Automotive Glossary
Automotive Glossary
Special | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | ALL
2 |
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2KThe common descriptive title for paints that require the addition of a hardener (without which they will not cure). | |
A |
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A.B.SAnti-lock braking system. | |
A.P.I.American Petroleum Institute. | |
A.P.I. (C)American Petroleum Institute classification for oils suitable for diesel (compression ignition engines). | |
A.P.I. (S)American Petroleum Institute classification for oils suitable for gasoline (spark ignition) engines. | |
A.P.I. SC/CCEngine lubricating oil classification suitable for basic petrol and diesel engines. | |
A.P.I. SG/CDEngine lubricating oil classification suitable for modern engines. | |
A/CAir Conditioning | |
A/C - Air ConditioningAir conditioning system that uses a refrigerant to remove heat from the air entering the passenger compartment. | |
A/D ConverterAn electronic device used to convert analog values to digital signals for electronic control units and instruments. | |
A/FAir/Fuel Ratio | |
A/TAutomatic transmission. | |
AbortThe term used when a test cannot be completed because of a problem with the VTS’s/DC’s testing equipment or the NT. No fee may be charged for the test. | |
AbrasionWearing away of a surface by some external force, such as sanding. | |
AbrasiveSubstance used to wear away or smooth a surface by friction. | |
AbrasivesSubstances used to wear away a surface by friction. | |
ABSAntilock braking system. | |
Absolute PressureThe pressure that exists when the forces of gravity are excluded from the actual pressure. Absolute pressure is equal to gauge pressure plus atmospheric pressure. | |
AbsorbThe penetration of a solid substance by a liquid as by capillary, osmotic, solvent, or chemical action. | |
AbsorptionOf heat: Takes in heat energy. Of sound: Takes in sound energy. | |
ABSVAir Bypass Solenoid Valve | |
ACAlternating Current | |
AC - Alternating CurrentAn electrical current that flows in forward and reverse bias alternately. | |
AccelerateTo speed up a process. | |
AccelerationIncreasing velocity or speed. | |
AcceleratorA substance that, when added to a paint, will speed up the rate of cure. | |
Accelerator PumpCarburettor pumping system that introduces flow of fuel into the carburettor choke (venturi) on acceleration, particularly when accelerating from low speeds. | |
AccumulatorA hydraulic device that dampens the pulses and retains a residual pressure in a hydraulic circuit. | |
AccuracyHow close the data given is to the true value. | |
ACEAAssociation des Constructeurs Europeens d'Automobiles. The European organisation that sets specifications for lubricants. There are three categories for engine oils. A for gasoline/petrol engines. B for light vehicle diesel engines. C for commercial vehicle diesel engines. | |
AcetoneA very fast evaporating solvent with high solvency for certain types of compounds and resins. Has a characteristic ether-like odour. | |
AcidAn inorganic or organic compound that (1) reacts with metals to yield hydrogen; (2) reacts with a base to form a salt. They are corrosive to human tissue and should be handled with care. Examples are hydrochloric acid, sulphuric acid, and nitric acid. | |
Acid RainForms when pollution is combined with water in the atmosphere. When sulphur dioxide and nitrogen oxides mix with water molecules, they form weak sulphuric and nitric acids. As the water evaporates, the acids gain strength and can etch the finish of any vehicle upon which they have been deposited. | |
Acidic CompoundsHarmful chemicals that are formed during combustion and can contaminate engine oil. Sulphur in fuel can form sulphuric acid which can cause corrosion, sludging and lubricating oil defects. | |
Ackerman PrincipleSystem of steering that produces wheel turning axes around a common point. | |
AcrylicA coating based on a polymer containing short chain esters of acrylic and methacrylic acid. One-pack Acrylics were once widely used as automotive topcoats, but have generally been replaced by water-borne base colours overcoated with two-pack Acrylic clear coats | |
Acrylic UrethaneA coating based on urethane chemistry which also includes acrylic chemistry as part of the cross-linked polymer backbone. | |
ACSAir conditioning switch. | |
ACT - Air Charge TemperatureAir charge temperature sensor measures the intake air temperature on fuel injection systems. | |
ActivatorA necessary component used to provide a chemical reaction to cure paints, resins and adhesives. | |
ActiveA system that takes action all the time as opposed to a passive system that waits for a specific event before reacting. | |
ACTSAir Charge Temperature Sensor | |
ActuatorsElectronic components that receive signals from an electronic control unit (ECU) and operate to make a system work. | |
AdapterGeneral term used to describe a device that allows one component to fit with another. | |
Adaptive MemoryA computer memory process that allows for changes in an open-loop mode. | |
AdditiveA chemical added to improve the properties or performance of something. | |
AdditivesChemical substances added to paint products in relatively small amounts to impart or improve desirable properties. Examples include UV screeners, flow agents, and fish eye eliminators. | |
AdhesionThe phenomenon by which one material is attached to another by means of surface attraction. | |
AdjusterGeneral term used to describe a component that changes the adjustment of something (brake shoes or brake bands for example). | |
AdviceGuidance offered by someone. | |
AEAuthorised Examiner – the organisation that operates and manages one or more VTSs and is responsible for controlling the quality of testing carried out. Except in the case of a ‘sole trader’ the AE is not a person but a legal entity (e.g. a company or partnership). | |
AerationAir mixture in a hydraulic liquid that reduces the performance of a hydraulic system. | |
Aesthetic ValueA value put on how nice or appealing something looks. | |
AFCAir Flow Control | |
AFMAir Flow Meter | |
AFSAir Flow Sensor | |
AgglomerateClumps of pigment particles which have formed loose clusters. Usually undesirable in paint, since agglomerates tend to settle out and exhibit poor colour or 'seeds', which are small granular deposits, other than dust, found in paint, varnish or lacquer colour. | |
AgitatorA paint stirrer. | |
Agitator CupPaint cup used with high metallics and pearls to keep the pigment particles in suspension by continually mixing the paint. This ensures better colour uniformity. | |
Air Bleed ValveAn automatic device used on fuel injection systems to provide fast idle during cold start and warm up. | |
Air CapFitted in front of a spray gun fluid nozzle to direct compressed air against the paint to form and shape an atomised cloud of droplets. | |
Air ChargeDescription of the amount of air taken into an engine on the induction stroke. | |
Air Cleaners/FiltersCanisters holding paper, plastic foam or gauze elements to trap dirt and grit. | |
Air DryThe ability of a coating to dry or cure to its ultimate hardness under normal atmospheric conditions, without baking or force-drying. Measurement of time required must state conditions such as temperature and humidity. | |
Air FlowMovement of a quantity of air past a point in a set time. | |
Air Flow MeterProvides information to fuel injection system electronic control unit (ECU) on engine load. Measures the mass of air entering an engine. | |
Air Flow Sensor PlateA plate used to sense the movement of air and therefore control fuel quantity. | |
Air GapThe gap between two parts of a component, such as the spark plug electrodes, an inductive sensor or an armature and field shoes of a motor or generator. | |
Air HornThe air inlet side of a carburettor or throttle body assembly. | |
Air InjectionAn emission control device that adds air to the exhaust to add oxygen for the conversion of hydrocarbons and carbon monoxide to water and carbon dioxide. Usually fitted upstream of a catalytic converter. | |
Air Intake DuctA pipe or similar used as part of the intake manifold or general system. | |
Air LineA pipe that delivers compressed air. | |
Air LockA bubble of air in a hydraulic system that can be compressed and therefore reduces the performance or causes failure of the system. | |
Air RatchetA ratchet wrench driven by compressed air. | |
Air ResistanceFriction force caused by, for example, a vehicle moving through the air. | |
Air SprayA system of applying paint in the form of tiny droplets. The paint is broken into droplets (atomised) by a spray gun as a result of being forced into a high velocity air stream. The shape and paint density of the resulting droplet cloud can be controlled by variations in air pressure, paint viscosity and gun tip geometry. | |
Air Temperature SensorElectronic device that provides information for engine management systems and frost warning indicator. | |
Air-fuel RatioThe air and fuel mixture strength ratio. | |
Airflow MeterProvides information to fuel injection system electronic control unit (ECU) on engine load. Measures the mass of air entering an engine. | |
Airflow Sensor PlateMechanical fuel injection component that moves in proportion to the air intake and sets fuelling accordingly. | |
Airless SprayA system of applying paint in which the paint, under extremely high pressure, is passed through a nozzle and breaks up into droplets as it enters the lower pressure region outside the gun tip. | |
AirlineA pipe that delivers compressed air. | |
ALCLAssembly Line Communications Link | |
ALCL/ALDLAssembly line communication or diagnostic link. A multisocket connector for attaching a diagnostic tool to a vehicle electronic system. | |
Alcoholics AnonymousA worldwide group of men and women who meet in order to help one another stop drinking alcohol and remain sober. | |
ALDLAssembly Line Data Link | |
AlignmentBringing into line. | |
AlkaliA chemical 'base' (loosely, the opposite of an acid). Certain types of alkalis have been used as fuel cell electrolytes. | |
AlkydA coating based on a polyester binder. Such polyesters are chemical combinations of molecules that contain more than one acid or alcohol group. | |
AllenA name used to describe a hexagonal key. | |
AlloyA mixture of metals and other elements to form a metal with specific properties such as phosphor bronze used for bushes. | |
Alternative fuelA fuel used in vehicles that comes from a source other than petroleum, such as ethanol made from corn and biodiesel made from vegetable oil. | |
AlternatorAn electrical generator attached to and driven by a motor vehicle engine. | |
Alternator BrushesSoft carbon brushes that conduct electricity to the field windings via the slip rings. | |
AluminiumNon-ferrous metal used as a substrate or a pigment. | |
Aluminium OxideSharp and hard abrasive - used in dry-flatting Production papers | |
Ambient PressureAir pressure in the surrounding area. | |
Ambient TemperatureTemperature of the air surrounding an object. | |
AmmeterInstrument for measuring electrical current. | |
AmmoniaA compound of nitrogen and hydrogen with the formula NH3. It is normally encountered as a gas with a characteristic pungent odour but can be included in a water based form into cleaning compounds for example. | |
AmperageStrength of an electrical current in amperes. | |
Ampere (Amp)Electrical unit for measuring the flow of electricity in a circuit. | |
Ampere-hour-rateDischarge rate used to describe what a battery will produce. For example, a 40Ah battery will produce 2A for 20Hrs. The 20hrs is an agreed value used to allow comparisons to be made. | |
AmplificationAn increased electrical voltage and/or current compared to say the original signal. | |
AmplifierAn electronic device that increases or allows an increased electrical voltage and/or current to flow. | |
AmplitudeThe maximum distance moved by a point on a vibrating body or wave measured from its equilibrium position. It is equal to one-half the length of the vibration path i.e. half the peak to peak value of a wave. | |
AmpsShort for Ampere (unit of electrical current) | |
AnaerobicUsed to describe a sealant that dries when air or oxygen is excluded. | |
AnalogA measuring process that uses a variable electrical current to provide a signal for computers and instruments. | |
Analog GaugeAn instrument readout that displays using a moving needle or similar method. | |
AnalogueA measuring process that uses a variable electrical current to provide a signal for computers and instruments. | |
Analogue GaugeAn instrument readout that displays using a moving needle or similar method. | |
Anionic ElectrodepositionOne of the electro-coating methods in which the body is charged positively and completely immersed in the negatively charged paint. Frequently used for OEM primer application, the resultant coating is known as 'E-coat' | |
Annual IncomeAmount of money you earn each year. | |
AnnulusThe outer gear with internal teeth on an epicyclic gear train. | |
AnodeA positive connection. | |
Anodised AluminiumA surface treatment for aluminium that adds an oxidised coating to harden the surface of the component. | |
AnodisingAn electrolytic surface treatment for aluminium which builds up an aluminium oxide coating, to provide better adhesion. | |
Anti-corrosiveProtective coating applied on metal surfaces to prevent corrosion. | |
Anti-freezeA chemical such as ethylene glycol, added to the cooling water of an engine to lower the freezing point for winter operation. | |
Anti-knockUsually used to refer to an additive that is added to fuel, which makes the burning process more controllable, resulting in reduced tendency to knock. | |
Anti-roll BarsSuspension component that reduces vehicle roll. | |
Anti-skinning AgentsChemicals added to a paint to help prevent the formation of a surface film during storage. | |
Anti-trap FunctionFacility to prevent electric windows closing and trapping something - your fingers for example! See also Bounce Back. | |
AntifreezeAdditive put in the cooling system to prevent freezing. | |
AntimonyA metal, which is added to lead, to improve its mechanical strength. Batteries were traditionally constructed with lead-antimony. | |
Antivirus SoftwareA software package that prevents computer viruses from damaging or destroying the system. | |
ApplicationAnother name for a computer program such as Microsoft Word. | |
Applied SolidsSolids that remain on the substrate being coated or painted. | |
APSAbsolute Pressure Sensor | |
APS - Absolute Pressure SensorA barometric pressure sensor used to compare atmospheric and manifold pressures in electric fuel injection systems. | |
AquaplaningThe effect when a vehicle's tyres tend to skid on top of water on the road. | |
AqueousDescribes a water-based solution or suspension (see 'waterborne'). | |
ArcingConduction of electricity across a gap. An arc is caused as contacts open. | |
AreaLength x width | |
ArmatureElectrical windings around the core fixed to the spindle of a motor or dynamo. | |
AromaThe smell of something such as perfume or worse... | |
AromaticsA type of solvent based on benzene ring molecules. | |
AsbestosFibrous silicate material that can be woven into an incombustible fabric. Requires special handling as it is a hazardous substance. | |
ASDMAirbag System Diagnostic Module | |
Aspect RatioRatio of two axes at right angles to each other such as the long and short sides of a rectangle. When applied to low profile tyres it refers to the width and depth and is shown as a percentage value in the tyre size marking. | |
AspirationBreathing or induction process of an engine. Non-turbocharged engines may be described as naturally aspirated. | |
AssessorThe teacher or tutor, who assesses the portfolio of evidence. | |
AsymmetricalA description of objects that are different on each side of their centre line. | |
ATDCAfter Top Dead Centre | |
ATDC - After Top Dead CenterATDC - Before Top Dead Centre. | |
ATDC - After Top Dead CentreThe position of the crankshaft when the piston has passed the top of the cylinder and is on the way down. | |
ATFAutomatic Transmission Fluid. | |
ATLAutomated Test Lane – These are lanes authorised by VOSA of use in the automated mode. | |
AtmosphereThe air that surrounds the Earth's surface. | |
Atmospheric PressurePressure in the atmosphere produced as a result of the Earth's gravity. Measured at sea level it has a value of 1 Bar, 14.7 psi or 100 kPa. | |
AtomSmallest particle in a chemical element that can take part in a chemical reaction. A single particle of an element. | |
AtomicRelating to the atom... | |
Atomic clockThis is a type of clock that uses an atomic resonance frequency standard as its timekeeping element. It is very accurate. | |
AtomisationThe formation of tiny droplets of liquid as in the paint spraying process. Atomisation is usually achieved by turbulence in an air stream, or a sudden drop in pressure. | |
AtomisedThe stage in which the metered air/fuel emulsion is drawn in to the airstream in the form of tiny droplets. | |
AtomizationBreaking up of fuel into fine particles during induction into an engine. | |
AtomizedThe stage in which the metered air/fuel emulsion is drawn in to the airstream in the form of tiny droplets. | |
ATSAir Temperature Sensor | |
AuralOf or relating to the ear or to the sense of hearing - aural diagnostics mean listening for faults such as a bearing noise or a misfire | |
Auto-boxSee Automatic Transmission | |
Automatic AdjustersBrake components that automatically take up wear to keep brake shoes or pads close to the drum or rotor. | |
Automatic ChokeA carburettor component using a bimetallic strip that operates at low engine temperatures to improve cold start and idle performance. Operates independently of the driver. | |
Automatic TransmissionA vehicle gearbox with automatic gear shifts based on engine speed and load conditions. Does not require individual gear shifts by the driver. | |
Auxiliary Air FlowUsed to describe a flow of air that bypasses the normal route. It is used to control idle speed or idle mixture. | |
Auxiliary Air ValveA valve used to control auxiliary air flow. | |
Auxiliary ComponentsComponents that are outside a specific system. For example, when working on the engine, an alternator would be described as auxiliary. | |
Auxiliary LightsExtra, non-essential lights such as front spotlights or driving lights. | |
Auxiliary shaftsShafts that are used on some engines for balance or to drive other components. | |
Avalanche DiodeA diode that conducts when a value voltage is applied. Used to protect circuits from overload. | |
AverageThe sum divided by the number of items. | |
Awarding bodyThere are several awarding bodies City and Guilds: AQA, Edexcel and OCR for example. | |
AWDTransmission system that uses all four wheels of a vehicle to provide a drive. This term is usually used on vehicles with a permanent four wheel drive that transfers drive to another axle when some loss of drive occurs on the main drive axle. The term 4WD or 4x4 is used for used for vehicles with selectable four wheel drive. | |
AWD - All Wheel DriveTransmission system that uses all four wheels of a vehicle to provide a drive. This term is usually used on vehicles with a permanent four wheel drive that transfers drive to another axle when some loss of drive occurs on the main drive axle. The term 4WD or 4x4 is used for vehicles with selectable four wheel drive. | |
Axial LoadingAlong the axis of a shaft. | |
Axial MotionMovement along or parallel to the axis of a shaft. | |
AxisThe centre line through a shaft or axle. The centre about which an object rotates or where the object is in equilibrium. | |
AxleHorizontal transverse shaft or beam with spindles on which road wheels are mounted. | |
Axle LoadingTerm used to describe the forces acting on an axle. | |
Axle MountingMethod of fixing the axle to the body or springs. | |
Axle StandsVehicle support equipment manufactured with a rated weight capacity. Used to support a vehicle when wheels are removed or when access to the underside is needed. Also known as jack stands. | |
Axle WindupA condition in an axle where the driven component locks and the axle casing attempts to rotate on its mountings. Usually caused when a differential lock or limited slip device is used and wheel spin is not possible such as on a dry road. | |
B |
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B-CANBody CAN or Basic CAN | |
B.ABritish Association old standard size of threads." | |
B.S. Kite MarkBritish Standards Kite Mark. The symbol of the British Standards Institute consisting of a triangle on its point with a capital B on its side above the triangle and a capital S inside the triangle. | |
B.S.FBritish Standard Fine size of thread." | |
B+Battery Positive Voltage | |
Babbitt MetalAn alloy of tin, copper, antimony and lead used as a coating for plain steel bearings. | |
Back EMFA voltage produced that tends to oppose the voltage that created it. | |
Back Plate(1) Non-rotating plate carrying the shoes of a drum brake. (2) Metal member carrying friction material of the disc brake pad. | |
Back PressureThe pressure build-up in the exhaust caused by the resistance to exhaust flow by pipe diameters and muffler baffles. Used in design to balance an exhaust to an engine. | |
Back-SandingTechnique of sanding a surface to taper the paint film away from the metal repaired area. | |
BackfireCombustion of fuel in the intake or exhaust resulting in a loud explosive noise. | |
BackingThe base material of flatting paper onto which abrasive grains are coated. For masking tape, the backing is the paper section without the adhesive. | |
Backing PadA supporting pad for abrasive disc and/or polishing pads that is attached to a polishing mop or a DA sander. In the compounding, glazing or polishing operation, a foam or wool polishing or glazing pad is attached on top of the backup pad. In dry sanding operations an abrasive disc is attached to the face of the pad. | |
BacklashThe clearance between two components, usually used to measure the running clearance of gear teeth. | |
BackupA second copy of work in case the original is damaged or destroyed. Should be stored away from the computer. | |
BaffleA part fitted behind the air cap in a spray gun to direct the air stream and reduce air turbulence. | |
BakingApplication of heat to cure and dry a coating. In automotive refinishing, baking is used to speed up the drying of air-drying finishes and is sometimes called force-drying. The metal temperature in refinish baking usually does not exceed 80°C (180°F). | |
Balance ShaftA rotating shaft geared to another shaft, usually the crankshaft that carries counterbalance weights to bring the shafts into harmonic balance. | |
Balance ValveA hydraulic device that controls the pressure in different parts of a hydraulic circuit. Used to balance front and rear brake actuation. | |
Balance WeightsSmall weights used to balance a shaft or a wheel. | |
BalancerAdditive used to balance colour formulae in proportion to size and pigment-to-binder ratio. | |
Balk RingA component of a synchromesh gear hub that provides a cone clutch and guidance of the outer hub to the gear dog teeth. | |
Ball BearingA bearing consisting of inner and outer tracks with a series of ball bearings in between. A single surface hardened steel ball. | |
Ball FlangeFlexible exhaust connection. | |
Ball JointsJoints that allow movement for suspension and steering. | |
Ball PivotA pivot that allows movement in several directions. | |
Ball ValveA simple valve that is closed off as a ball moves. | |
Ballast ResistorElectrical resistor used in low tension circuit to regulate ignition coil output when the engine is running and is by-passed during starting to give an increased spark voltage for cold starting. | |
BandwidthThe maximum amount of information (bits/second) that can be transmitted along a channel. | |
Banjo JointA hydraulic joint consisting of a hollow through bolt and a hose connector that looks like a banjo and from which it gets its name. | |
BarMeasurement of pressure - one atmosphere. | |
BAROBarometric Pressure | |
BARO (Barometric Pressure)Air or gas pressure measured in a standard unit. (Pascal, psi, bar) | |
Barrier CreamUsed to help prevent skin damage when working, for example, with oils. | |
BaseTerminal of a transistor that becomes conductive to the emitter when energised. The trigger terminal of transistors and thyristors. | |
BasecoatA colour coat requiring final protection in the form of a sprayed clearcoat. The basecoat provides colour effects and appearance, while the clearcoat provides gloss as well as UV and chemical resistance. | |
Basic skillsReading, writing, speaking in English (or Welsh) and using numbers sufficiently well to be able to function in society and at work. Key skills and basic skills overlap at levels 1 and 2. | |
BATBattery | |
Bath tubAn old type of combustion chamber looking like a bath tub when the cylinder head is turned over. | |
BatteryA chemical device that will give out an electrical current when connected into a circuit. | |
Battery CarrierA tray to hold the battery, usually under the bonnet. | |
Battery GreasePetroleum jelly used on battery terminals. | |
Battery moduleA generic term meaning a collection of battery cells and control systems. Often relates to EVs or HEVs. | |
Battery PostsThe main connections on a battery. | |
Battery terminalSee Battery Post | |
Battery VoltsA term used to describe the voltage of the particular system. This is often 12V - but could be 14V when the engine is running. | |
BCMBody Control Module | |
BDCBottom dead centre. The position of the crankshaft when the piston is at its lowest position in the cylinder. The crankshaft is at 180° of rotation from the top dead centre 0° position. | |
BeadPart of the tyre. | |
Beam AxleType of non-independent suspension. | |
Beam SetterEquipment used to check the alignment of vehicle headlights. | |
Bearing CapHalf-round parts that holds the big end and main bearings into place either on the con rods or engine block. | |
Bearing ClearanceThe freeplay between a bearing shell and journal. | |
Bearing Nip or CrushApplies to the applied grip of a split shell bearing when the two halves are tightened together. | |
BearingsComponents used to support a shaft and allow rotation. | |
Bell HousingCover over the clutch assembly. Usually joins the gearbox to the engine. | |
BenignA benign condition is one that is not usually serious or harmful. Zero emissions for example. | |
BenzoleHydrocarbon fuel additive and octane improver. | |
Bevel GearsGears cut at an angle from the periphery so that they can transmit a drive through an angle. An example is the final drive crown wheel and pinion. | |
BHPBrake Horse Power | |
Bi-Metal SpringA spring made of two metals that expand differently with temperature change. This changes the tension as temperature changes. | |
BiasTowards one side or one polarity. | |
BiasedFavouring one thing over another. | |
Big EndEnd of the con rod that fits to the crankshaft. | |
Big End BearingsThe journals and shell bearings on a crankshaft that carry the big ends of the connecting rods. | |
Bimetal StripTwo metals bonded together so that when heated, the different rates of expansion cause the strip to bend. The amount of bend is proportional to the temperature. | |
Bimetal Thermostatic SpringA spring that changes tension with temperature. | |
Bimetalic ValveSee Bi-metalic Valve. | |
Bimetallic ValveA valve that operates when a temperature change moves a bimetal strip. | |
BinaryA system of numbering using 0 and 1 and used in computer operating systems. | |
Binary CounterAn electronic device that counts in binary (1s and 0s) by using logic gates and basic memory devices. | |
Binary digitA binary digit or bit is the basic unit of information in computing and telecommunications; it is the amount of information that can be stored by a device or other physical system that can normally exist in only two distinct states - 1 or 0, on or off for example. | |
BinderThe component in a paint material that forms the film. So-called because it binds the pigment and any additives present into a solid durable film. | |
BindingTerm used to describe one component sticking or rubbing against another. | |
BiodegradabilityThe capacity of a material to decompose over time as a result of biological activity, especially to be broken down by microorganisms. | |
BitA binary digit or bit is the basic unit of information in computing and telecommunications; it is the amount of information that can be stored by a device or other physical system that can normally exist in only two distinct states - 1 or 0, on or off for example. | |
Black boxEquipment that records information about the performance of an aircraft during flight – or a vehicle during its normal use. | |
Blade ConnectorAn electrical cable connector consisting of a blade and spring sided socket. | |
Blanking PlugsScrewed plugs used to blank off or block off a test port or adjustment point. | |
BleedThe act of removing air from a liquid system. | |
Bleed NippleA small nipple valve that allows connection of a pipe and is operated by loosening. | |
BleedingA defect in which pigment from a lower coat of paint diffuses into an upper coat and discolours the latter. A non-bleeding colour is one that is not soluble in materials used over it and consequently does not work up into succeeding layers. Body filler may also cause bleeding if an excessive amount of hardener is added. | |
BlendingRepainting of panels or parts of panels and fading out the new colour onto adjacent prepared panel work to render the repair invisible. Normally only carried out on basecoat-and- clear finishes, as it is very difficult to blend a direct gloss paint finish. | |
Blending FlapsFlaps used to mix hot/cold and fresh/recirculated air in a heater system. | |
Blipped ThrottleDescription of a 'quick press' of the throttle to make the engine rev up. | |
BlisteringThe development of hollow bubbles or water droplets in a paint film. Blistering is usually caused by the expansion of air or moisture trapped beneath the film. It can occur rapidly or any time after application as the paint film ages. Blistering may also occur from the presence of unreacted acid within the paint film. | |
Block diagramA diagram of a system, in which the main parts or functions are represented by blocks connected by lines, which show the relationships between the blocks. | |
Blocker BarGeneral term used to describe a bar that prevents an action of some kind. | |
BloomingA powder-like deposit which sometimes forms on the surface of a paint. It is often the result of a solvent component partly dissolving the pigment(s) and then depositing them on the surface when the temperature is below the 'dew point',( i.e. the temperature at which moisture will condense on the surface) | |
Blow BackIgnition of fuel in the inlet manifold causing a flame to rise out of the air intake through the carburettor. | |
Blower MotorA motor that uses a fan to assist in moving air. | |
BluetoothWireless Technology. A chip is responsible for the transmission of data between a wide range of devices (mobile phone and hands-free system) through short range digital two-way radio. | |
BlueVisionTrade name for 'blue' headlight bulbs produced by Philips. | |
BlushingThe appearance of whitish or "cloudy" areas in a paint finish, caused by absorption and retention of moisture in a drying paint film. | |
BMAPBarometric/Manifold Absolute Pressure Sensor | |
Bodied VehiclesA bodied vehicle is defined as ‘a vehicle with a structure consisting/comprising of a floor pan and panels which, with a roof fully encloses the vehicle occupants and without a roof encloses them other than where the roof would be’. As a guide, if the driver sits in the vehicle with surrounding structure it would be classed as bodied. | |
BodyMain portion of motor car. | |
Body FillerA heavy-bodied 2K plastic filler material which cures very hard and is used to fill small dents in metal and plastic panel work. | |
BodyingThickening of paint in the can, usually due to evaporation of solvents or volatile material because of poor fitting lids or exposure to heat or air. | |
BondAttraction between two things such as to cause them to stick together. | |
Bonding CablesCables or wires used to connect different panels together. | |
Bonding ResinAdhesive often used on friction linings. | |
BOOBrake on/off switch | |
Boost PressureThe amount of increase above atmospheric pressure provided by a supercharger. | |
Booster FanSee blower motor. | |
BootUsually made of rubber, a cover for a moving component such as a track rod end. | |
Boots/GaitersA rubber (or similar) boot used to cover working components. It is used to keep dirt out and in some cases lubrication in place. Also slang for alligator... | |
Bore (cylinder)The internal part of a hollow cylinder in which a piston is located. | |
Boring BarUsed to cut cylinder bores. | |
Boron steelBoron steels possess hardenability equivalent to that of much higher carbon steels and more expensive low alloy heat treatable steels. Tempering toughens boron steels. The addition of only 0.001-0.003% soluble boron to a suitably protected base steel can produce an increased hardenability compared other steels. | |
BoschRobert Bosch GmbH is a technology-based corporation which was founded by Robert Bosch in Stuttgart, Germany in 1886. | |
BossA reinforcing section around a cylindrical bore in a component. | |
Bottom Dead CentreThe position of the crankshaft when the piston is at its lowest position in the cylinder. | |
BounceVehicle body suspension movement when hitting bumps. | |
Bounce TestA manual test of suspension dampers (shock absorbers) by pushing down on the suspension and observing the oscillations when released. | |
Bounce-backMovement of an electric window as it hits an obstruction - and bounces back (opens again). | |
Boundary lubricationThis form of lubrication is essentially a breakdown of hydrodynamic action. At high loads or low speeds, the pressure of the oil film cannot prevent metal-to-metal contact. So the opposing surfaces partially ride on an oil film and partially rub together as surface high points come in contact. Lubrication is provided by lubricant decomposition products or surface-active additives which form a thin, soft, solid film on the metal surfaces and prevent metal-junction adhesion. | |
Bourdon TubeA U shaped tube used to measure vacuum. | |
Box SectionsParts of the vehicle body - chassis and structural members. | |
Boxer EngineA horizontally opposed engine. | |
BP SensorA barometric pressure sensor. | |
BPSBack pressure Sensor | |
BPTBack Pressure Transducer | |
Brake(1) Device to retard the motion of a vehicle or to prevent inadvertent movement when parked. (2) Dynamometer for measuring the power of an engine, originally a friction brake by which torque could be measured. Also brake dynamometer (informal). | |
Brake AccumulatorA pressure container fitted into pumped hydraulic systems to maintain a reserve of pressure if the pump fails. They also smooth out the pump pulses in the system. | |
Brake AdjusterA mechanical device for taking up the free play in brake components. Can be either manually or automatically operated. | |
Brake BalanceThe splitting of brake effort to each axle in relation to the optimum that the axle can provide. | |
Brake BandA friction material lined strap around a epicyclic gear annulus. Operated by hydraulic pressure to hold the annulus for gear ratio selection. | |
Brake BoosterSee brake servo. | |
Brake CaliperThe fixed component of a disc brake holding the pistons that apply an inward force to press the brake pads onto the rotor. | |
Brake CylinderThe wheel cylinders of hydraulic brakes in the brake unit. | |
Brake DrumRotating drum inside which brake shoes operate. | |
Brake FadeReduction of braking effort resulting from overheating of friction surfaces, or other transient effect. | |
Brake FluidA special liquid used in hydraulic brake systems. Always check data because some types should not be mixed. | |
Brake Horsepower (bhp)A measure of the power output from an engine when measured with a dynamometer using a brake applied to the engine flywheel. The engine effort to overcome the braking force gives the bhp value. | |
Brake LinesThe hydraulic pipes and hoses of the brake system. | |
Brake LiningThe friction material attached to brake shoes and pads. | |
Brake LinkageA general term to describe components that link different parts of the brake system together. | |
Brake PadA steel plate with a bonded friction lining used on disc brakes. Similar to the brake shoe of a drum brake. | |
Brake RollersRollers used to drive the wheels of a vehicle for brake testing purposes. | |
Brake ServoA mechanism (vacuum or hydraulic) that increases the braking effort applied by the driver. | |
Brake ShoesPart of drum brake carrying linings. | |
Braking EffortThe force applied to the brakes. | |
Braking ThrustForces that are caused by braking. | |
Breakout BoxA terminal box for carrying out diagnostic tasks on electrical and electronic systems. | |
Bridge RectifierA type of rectifier using four or more diodes to give full wave rectification. | |
BridgingA characteristic of undercoat performance that occurs when a scratch or surface imperfection is not completely filled, leaving a cavity underneath. It i caused by under-reducing the primer or using too fast a solvent and can lead to the appearance of sand scratches in the finished repair. | |
BronzingThe formation of a metallic-appearing haze on a paint film. | |
Brush End PlateA plate used to hold brushes in contact with a commutator. | |
BrushesPieces of carbon or metal ending in wires or strips. Contacts onto rotating slip-rings or generator/motor commutators. | |
BTDCBefore Top Dead Centre | |
BTDC - Before Top Dead CenterBTDC - Before Top Dead Centre. | |
BTDC - Before Top Dead centreThe position of the crankshaft before the piston has passed the top of the cylinder and is still on the way up. | |
BtuBritish Thermal Units | |
BuffingA technique used to polish an area to remove sanding marks or surface imperfections (see Polishing). | |
Buffing CompoundSoft paste containing various grades of fine abrasives suspended in a neutral medium, used to eliminate fine scratches and polish the topcoat. | |
BuildThe amount of paint film deposited on a substrate (the depth or thickness of which is measured in microns). | |
BulkheadSubstantial structural panel of vehicle body in front of passenger compartment. Also known as a firewall. | |
Bump CapA hard hat. | |
Bump SteeringSteering action that results from hitting a bump. | |
Bump StopA rubber spring that limits and dampens the movement of a spring to prevent excessive deflection and spring damage. | |
BuoyancyThe ability to float in liquid or in air. | |
BurrsTerm used to describe rough edges on metal components. | |
BusA motor vehicle which is constructed or adapted to carry more than eight seated passengers (see also Minibus). | |
BushCylindrical sleeve forming a bearing surface for a shaft or pin. | |
Bushes (rubber)A metal and rubber composite bearing that provide both a limited range of movement and insulation from road vibration. | |
Buss BarA conductor in a fuse box or other electrical distribution device. | |
ButylSynthetic rubber impervious to oxygen. | |
Butyl AcetateA medium-evaporating solvent used in paint. | |
BypassA secondary route in a system that allows gas, liquid or electricity to flow outside of the main route. | |
Bypass ValveIn a lubrication system a valve that allows oil to bypass a filter. | |
C |
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CCelsius | |
C Classification (SAE)Engine oil suitable for diesel engines. The second letter in the classification denotes the quality and minimum conditions that the oil must meet. | |
C.F.P.PCold filter plugging point. Applies to diesel fuel with a cold weather additive." | |
C3IComputer Controlled Coil Ignition | |
Cadence brakingAn emergency braking procedure using rhythmic application and release of the brakes to strike a compromise between slowing down with locked wheels, so retaining the ability to steer. | |
CadmiumA metal used in the manufacture of durable but expensive red and yellow pigments. | |
CalciumA soft grey metallic element used a component in driers and pigments. | |
Calcium CarbonateAn extender pigment, also known as "whiting." | |
CalibrateThe act of making sure a piece of measuring equipment is accurate. Often this is done by checking it against equipment that is known to be good. | |
CalibratedThis means that a piece of measuring equipment is accurate. Often this is done by checking it against equipment that is known to be good. | |
Calibrated ApertureAn accurate size hole to control flow. | |
Calibrated FloatThe float used in a hydrometer. It is designed to work accurately (calibrated) usually at 15 degrees Celsius. | |
Calibration ResistorA variable resistance that is used to set the basic position of a circuit. | |
CaliperIn a disc brake system, the mechanism that brings brake pads to bear on the disc by a clamping or pinching action, similar to that of the jaws of a Vernier caliper. | |
Caliper PistonA slave cylinder in a brake caliper. | |
CALPAKCalibration Pack | |
Cam(1) A shaped or profiled component that produces linear or angular motion or lift of a follower. Except in the steering box, most automotive cams are in the form of non-circular wheels which impart motion to the follower by their rotation. (2) A camshaft (informal). Misleading usage, as for instance twin cam to describe an engine with two camshafts. | |
Cam BeltBelt, usually made of reinforced rubber, which drives the cam from the crank. | |
Cam LinkageA cam shaped (egg shaped) part. | |
Cam LobeHigh point of a cam which operates components. | |
Cam PlateA plate with one or more raised areas in the shape of a cam. Used in rotary diesel injection pumps to supply high pressure injection. | |
Cam RingA shaped ring with a cam shape. | |
Camber(1) Convex arched curvature of a (usually horizontal) surface. (2) Average curvature of the chord wise section of an aerofoil. (3) Mildly arched profile of a road or pavement. (4) Inclination of the plane of a wheel to the vertical plane of symmetry of a vehicle. Camber is considered positive if the wheel leans out towards the top, and negative if it slopes inward. | |
CamshaftShaft on which suitably phased cams are mounted, as for example to operate intake and exhaust valves of an engine. In four-stroke engines the camshaft rotates at half crankshaft speed. | |
CANController Area Network. A protocol for a multiplexed system of control and communication on a vehicle. | |
CAN BusThe actual circuit on which the CAN signal/message is transmitted. It is usually a pair of wires but fibre optics have been used. | |
CAN messageThe information transmitted on a data bus from one node to another. | |
CANPCanister Purge Solenoid Valve | |
Cap (Tire Valve)Air Valve. Secondary air valve for an inflated tire. | |
CapacitanceAn ability to store an electrical charge in two conductors separated by an insulator. | |
CapacitorElectrical/electronic device consisting of two plates separated by an insulator. It is capable of holding a charge. | |
Capacity (engine)Applied to the sum total of the swept volumes for all cylinders in an engine. Also known as 'total displacement'. | |
Carbon BlackA black pigment manufactured by collecting the carbon resulting from incomplete combustion of natural gas. | |
Carbon Monoxide (CO)Polluting, odourless, toxic (poisonous) gas produced by incomplete combustion of fuel. | |
CarburetorSee Carburettor. | |
CarburettorDevice for Vaporizing liquid fuel and mixing it in appropriate proportions with a stream of air, prior to combustion in an engine. | |
Cardan JointA drive shaft universal joint consisting of two yokes and a cross bearing. Also Hooke's joint. | |
CASCrank Angle Sensor | |
CastingA metal forming process where molten metal is poured or injected into a mould. | |
Castor(1) Originally an undercarriage member with a vertical pivot axis behind which the wheel trailed, so that the wheel aligned itself to its direction of motion. (2) Steering geometry, parallel to the direction of travel, in which the steering pivot is inclined away from the vertical in order to give the effect of castor as described in 1. Also castor offset and castor trail. Small pivoting wheel attached to piece of furniture to facilitate movement. | |
Castor AngleAngle in side elevation between the steering and vertical axis. | |
CatalystA substance that causes a chemical reaction when it is mixed with another substance. | |
Catalytic ConverterUses platinum, palladium and rhodium to change pollutants in exhaust gases to harmless substances. | |
Catch UpThe process by which testing test data recorded while testing under Emergency Testing is subsequently entered via the VTS Device. | |
CathodeA negative connection. | |
Cationic electrodepositionOne of the electro-coating (E-coat) methods in which the body is charged negatively and the paint positively. The cationic method is superior to the anionic method in terms of corrosion resistance. Frequently used for OEM primer application. | |
CaulkingSealing used in joints to prevent the passage of fluid (commonly moisture) or gas. | |
CavitationThe formation of cavities in a structure or of gas bubbles in a liquid, or of a vacuum or partial vacuum as between a body moving in a fluid and the fluid. | |
CCCubic Centimetres | |
CCACold cranking amps (a rating for batteries) | |
CCMCComite des Constructeurs d'Automobile du Marche Commun. The European organisation that set standards for engine lubricants. This organisation has been replaced by ACEA (Association des Constructeurs Europeens d'Automobiles). | |
CD ROMCompact Disk Read Only Memory. Stores up to 800Mb of data. The data is 'read only' which means that you cannot change or overwrite it. | |
CDICapacitor Discharge Ignition | |
CDI (Ignition)Capacitor discharge ignition system that uses a capacitor to produce the high tension for arcing across the electrodes of the spark plug. | |
CEABCold Engine Air Bleed | |
CECUCentral Electronic Control Unit | |
CellThat part of a battery made from two dissimilar metals and an acid or alkali solution. A cell stores chemical energy for use later as electrical energy. | |
Cell CapsRemovable covers for a battery cell. | |
Center BearingsSee Centre Bearings. | |
Center of GravitySee Centre of Gravity. | |
Centre BearingsBearings usually used to support a rotating shaft - at its centre. Many RWD propshafts have a centre bearing for example. | |
Centre LinkThe centre track rod of a three-part steering system which connects the steering box drop arm to the idler and the two outer track rods. | |
Centre of GravityThe point about which an object would balance in all directions. Also the point about which it can be said that gravity is acting on something. | |
Centre Point SteerSteering geometry, parallel with the vehicle axis, in which wheel camber and steering swivel axes meet at the centre line of a steered wheel at ground level. | |
Centrifugal ForceThe outward movement felt as a car turns a sharp corner. | |
Centrifugal UnitMechanical system using weights attached to a shaft. These move out against spring force as the shaft speed increases. Senses shaft speed for ignition advance and diesel pump speed. | |
CERCold Enrichment Rod | |
CESSCold Engine Sensor Switch | |
Cetane NumberApplies to diesel fuels as a measure of the delay in ignition after injection. A higher number indicates a shorter delay. | |
Cetane RatingSee cetane number. | |
CFICentral Fuel Injection | |
CFI (Fuel Injection)Usually centre point fuel injection system but sometimes used for continuous fuel injection. | |
cfmCubic Feet Per Minute | |
ChaffingUsed to describe the unintentional action of one component rubbing against another. | |
ChalkingThe degradation of a paint film by gradual erosion of the binder, typically due to weathering. It is common in ageing red finishes and is characterized by a pinkish haze and loose pigment particles on the surface of the paint | |
ChamoisA soft suede leather formerly from the skin of the chamois antelope but now more often made from sheepskin. | |
Charcoal CanisterA part of a fuel evaporative (EVAP) system. The charcoal absorbs petrol vapour during fuel tank venting and returns the fuel to a reverse air flow and into the engine under specific conditions. | |
Charge CurrentSee charge rate. | |
ChargingProcess of building up the level of charge in a battery or capacitor. | |
Charging RateThe recommended rate of charge for a battery. Usually one tenth of the amps in the Amp hour rate for one and a half times the hours for a fully discharged battery. | |
ChassisStructural lower part of a vehicle to which the running gear and body are attached. The true chassis is now evident only in larger vehicles. | |
Check ValveA one way valve, using a plate or ball and spring, that permits fluid flow in one direction only. Used in hydraulic systems to retain a residual pressure. | |
CheckingA type of paint film defect in which cracks in the film begin at the surface and progress downward. The result is usually a straight v-shaped crack which is narrower at the bottom than the top. | |
ChecksumA checksum is a count of the number of bits in a transmission unit that is included with the unit so that the receiver can check to see whether the same number of bits arrived. If the counts match, then one can assume that the complete transmission was received. | |
Chemical BondA reaction between atoms that causes a force such as to create a bond. | |
Chemical Cartridge RespiratorA respirator which uses a cartridge containing various chemical substances to purify inhaled air of certain gases and vapours. | |
Chemical StainingSpotty discolouration of the topcoat sometimes caused by environmental conditions (acid rain, tree sap, etc.) It can also be caused by improper activation of body filler which leads to staining in the subsequent layers of topcoat. | |
Chemical TreatmentA process that uses chemical to bring about a change in something. | |
ChipDescription of an integrated circuit where the circuit is built on a silicon chip. | |
ChippingSmall flakes of a finish losing adhesion from the substrate. Usually caused by the impact of stones or hard objects. | |
ChokeA restriction in a carburettor. The term is used to describe either the venturi as in single or twin choke carburettor, or for the cold start device. | |
Choke FlapThe butterfly type valve that restricts the flow of air. | |
Chopper ModuleAn electronic circuit or unit that switches a supply on and off rapidly. | |
ChromaThe level of saturation or intensity and richness of a colour. De-saturated or "dirty" colours have less chroma; saturated or "clean" colours have more chroma. | |
ChromateA chemical compound used as a component in primers to provide corrosion protection to metal. | |
Chromate RinseNewly manufactured vehicle bodies are completely immersed in a chromic acid solution after zinc or iron phosphating to passivate the metal at the base of cracks and pinholes in the phosphate. Chromate rinsing, as used in modern mass-production paint preparation, will greatly increase corrosion resistance. | |
CIDcylinder identification sensor | |
CircuitA complete conducting path. | |
Circuit BoardA board used to construct an electronic circuit. | |
Circuit BreakerA switch to turn off the current flow in a circuit. Can be manually or automatically operated. | |
Circuit diagramA diagram using symbols for electrical and electronic components that represents a real circuit. | |
CircumferenceThe boundary line of a circle. | |
CISContinuous Injection System | |
CKPCrankshaft Position Sensor | |
CKP SensorAbbreviation for the crankshaft position sensor. | |
Clamp PlateA simple plate to hold another item securely. | |
ClarifyTo make clear. | |
ClaysClay is a naturally occurring material composed primarily of fine-grained minerals. It is used in some cases to act as a very fine abrasive for improving paintwork. | |
CleanerMaterial used to remove dirt and other impurities from a substrate prior to painting. | |
Clear CoatThe transparent, non-pigmented top coat that is applied over a coloured base coat paint. Most modern cars have factory-applied clear coat paints. Clear coat paint increases paint durability, gloss, and resistance to harmful environmental effects such as ultra-violet radiation. | |
ClearanceA gap between two components. | |
Clearance FitThe relationship between the dimensions of two components where one fits inside the other. In this instance the fit is one where the inner dimension of the outer component is greater than the outer dimension of the inner component. | |
Clearance SizeA drilling size slightly larger than the nominal size of a thread. | |
Clearance VolumeThe space above a piston at top dead centre in a cylinder. Includes the combustion chamber and any other volume formed by the thickness of gaskets, etc. | |
ClipboardA temporary area used to store copied information. | |
Clock springThese are generally made of rectangular section material, flat strip, with round edges. They are general used as brush springs in D.C. motors. Also known as spiral springs | |
CloggingCondition where abrasive paper becomes clogged by the abraded surface coating. | |
Closed CircuitApplied to an electrical circuit when the switch is 'on' or the circuit is continuous. | |
Closed LoopA system where a change in the output causes a changed input which in turn changes the output and so on... | |
Closed Loop SystemElectronically controlled system, which adjusts settings by feedback from sensor signals that are monitoring the performance of actuators in the system and comparison with the pre-programmed map. | |
CloudingThe formation or presence of a haze in a liquid such as a paint film. | |
ClutchA device to allow drive to be connected and disconnected. In a starter motor a clutch is used to only allow drive to pass one way - starter to engine, NOT engine to starter. | |
Clutch (Transmission)Disengages / Engages drive from the engine. | |
Clutch ForkSee Release Fork. | |
Clutch LinkageMechanism to connect the pedal to the clutch release bearing. May be cable, electrically or hydraulically operated. | |
Clutch PackA set of friction plates and pressure plates in a multi-plate clutch. | |
Clutch PlateThe friction plate used as part of a clutch. | |
CMPCamshaft Position Sensor | |
CMP SensorAbbreviation for the camshaft position sensor. | |
COCarbon Monoxide | |
CO2Carbon Dioxide | |
CoachA motor vehicle which is constructed or adapted t carry more than 16 seated passengers, with a DGW of more than 7,500kg and a maximum speed in excess of 60mph. | |
CoachingCoaching is a method of directing, instructing and training a person or group of people, with the aim to achieve some goal or develop specific skills. | |
CoalescenceThe fusing or flowing together of liquid particles. The term is frequently applied to waterborne coatings, which require coalescence to form a continuous film. | |
CoastingDriving on very light throttle at a constant speed. | |
CoatingThe act of applying paint or the actual film left on the substrate by an applied paint. A single coat may be produced by two passes of a spray gun, one overlapping the other in half steps. A double coat is two single coats with little or no flash-off time between them. | |
CobwebbingThe tendency of sprayed paint to form strings or strands rather than droplets as it leaves the gun. May be caused by too fast or improper solvent, paint too thick or air pressure too low. | |
Coefficient of FrictionA value between 0 and 1 that indicates the ability of two materials to grip each other when sliding or rolling in contact with other. | |
Coil (Ignition)An electrical transformer that increases the battery voltage to a high tension capable of arcing across the gap of spark plug electrodes. | |
Coil SpringA spring that consists of a single length of bar wound into a helix (coil). | |
Cold Cranking RatingApplies to a battery's ability to provide a minimum current for a minimum time for starting a cold engine. | |
Cold Start EnrichmentAn increase in the amount of petrol mixed with the air under cold starting conditions. | |
Cold Start ValveAn extra valve used only when starting from cold. | |
Cold StartingCranking the engine so that it will start and run under cold conditions. | |
Cold-CrackingCracking of a paint film resulting from a sudden drop in temperature, or repeated cycling from high to low to high temperatures. | |
Cold-start ValveAn extra valve used only when starting from cold. | |
CollectorTerminal of a transistor that becomes conductive to the emitter when the base is energised. | |
ColletSmall half-round and tapered components used to fix a valve stem to its cap. | |
ColourThe visual appearance of an object that can be described in terms of hue, value, and chroma. Colours are seen differently by different people and under different lighting conditions. | |
Colour CoatThe single-stage or basecoat that provides the visible colour of a coating system. | |
Colour MatchAchieved when the applied colour duplicates all aspects of the original colour's appearance in terms of hue, value, and chroma. | |
Colour RetentionThe ability of a paint to maintain colour under exposure to light, heat, moisture or other conditions of use. | |
Colour SandingThe sanding of a cured or dried paint film to prepare it for polishing or recoating. | |
CombustionThe burning of fuel in air. | |
Combustion ChamberArea above the piston when it is at TDC where the combustion takes place. | |
Combustion KnockAdvanced or quick detonation of fuel in a cylinder where the resultant pressure rise causes a shock wave through the piston, crankshaft and engine block. | |
Combustion StrokeThe third stroke of the four stroke cycle when the fuel is burnt to produce heat energy, expansion of the air/fuel charge and power on top of the piston. Also known as the power stroke. | |
CommunicationThis is a process of transferring information from one entity to another. An exchange of thoughts and information if human. | |
CommutatorRotating contacts for electrical windings on a generator or motor armature. | |
CompensatingA strategy that involves adjusting something up or down to more closely approximate the required or ideal value. | |
CompensatorProvides equal force to mechanically braked wheels. | |
Compliance CoatingA coating whose volatile organic compound (VOC) content does not exceed that allowed by regulations. Compliance coatings may be waterborne, low solvent, or powder. | |
Composite MaterialsMaterial made up of constituents that remain recognisable. | |
CompoundPlace where cars are taken when they die, or dogs when they get lost...A chemical where the two or more elements they contain combine at the molecular level - salt for example is a compound of sodium and chlorine (sodium chloride). | |
Compound Gear TrainTwo or more pairs of gears. | |
CompoundingThe use of an abrasive material, either by hand or machine, to smooth and enhance the gloss of the applied topcoat. | |
CompressionThe reduction in volume of a gas when it is squashed. The gas pressure increases and the temperature rises. | |
Compression Ignition (CI)Fuel ignited by heated air (diesel). | |
Compression RatioThe ratio between the TOTAL volume of a cylinder (swept volume plus clearance volume) and the CLEARANCE volume (volume above the piston at TDC - the combustion chamber). | |
Compression RingA piston ring that helps to contain combustion pressure. | |
Compression SpringA spring that is designed to provide force when compressed. | |
Compression StrokeThe second stroke of the four stroke cycle when air or the fuel/air mixture is compressed. Compression is necessary for clean and efficient combustion of the fuel. | |
CompressorElectrically or mechanically driven pump used to increase pressure of a gas or liquid. | |
Compressor WheelPart of a turbocharger that pumps extra air into the intake and therefore the engine. | |
CompulsoryMust be completed. | |
Computer ApplicationPrograms such as Word, Excel and PowerPoint. | |
Computer CrashAn event that causes the computer to become inactive. This can often result in the loss of unsaved work. | |
Con RodShort for connecting rod, this joins the pistons to the crankshaft. | |
ConcentricA term that describes objects that revolve or are fitted around a common centre. | |
ConciseExpressing a lot but in few words. | |
Condenser1. Part of an air conditioning system positioning in the outside air stream. It gives off heat to atmosphere as a refrigerant condenses. 2. Alternative name for a capacitor in an ignition system. | |
Condenser (A/C)A heat exchanger in an air conditioning system that is similar to, and fitted in front of, the coolant radiator where it passes heat energy to the air stream passing through it. Operates by condensation of the refrigerant from gas to liquid by pressure and heat loss. | |
Condenser (Ignition)An electrical capacitor that is used in a contact breaker ignition system. | |
ConductionTransfer of electrical or heat energy along material. | |
ConductorA material that allows free movement of electricity or heat through it. | |
Conductor FoilGeneral term to describe a type of 'flat' wiring harness. | |
Cone ClutchA simple clutch shaped like a cone. Used as part of a synchromesh mechanism. | |
Cone PulleyA pulley shaped like a cone such as to allow different ratios to be set by the position of a drive belt. | |
Confidential InformationInformation that is private and should be protected. | |
Connecting RodThe engine component that joins the piston to the crankshaft. | |
Constant Velocity JointA drive shaft joint that transmits drive through an angle without changes in speed. | |
Construction and UseThe UK Construction and Use Regulations that cover the legal requirements on manufacturers and users of road vehicles. | |
Constructive feedbackA way of giving feedback to somebody so that they feel valued and that they can improve what they did based on your comments. | |
ConsumptionThe rate at which a vehicle uses fuel. | |
Contact BreakersMechanical spring-loaded switch located in the distributor of an ignition system and actuated by a rotating cam. It makes or breaks the ignition circuit to control the coil output and delivery of a spark to the spark plug. | |
ContaminantSomething which contaminates; an impurity; foreign matter | |
ContaminantsAny polish, wax, tree sap, tar, oil, etc., that would damage the paint film or spoil the adhesion of a new paint film. | |
ContinuityThe condition of an electrical circuit when a current will flow. | |
Continuous InjectionInjectors that inject or 'squirt' all the time. | |
Continuous Injection SystemsInjection systems where the supply to the inlets is active all the time but may only 'spray' on the intake stroke due to the lower pressure. | |
Contouring(see Mapping) | |
ContractAgreement between parties enforceable in law. | |
ContractionA decrease in size. For example, when a metal rod is cooled it decreases in length and diameter. Opposite of expansion. | |
Control FlapA flap that is used to control something! Air temperature for example. | |
Control PlungerPart of fuel injection system. Regulates fuel delivery against air flow. | |
Control PumpA pump that provides a set pressure. | |
ConvectionTravel of heat by movement in heated fluids due to a reduction in density and consequent rise of the hotter material. | |
Conversion CoatingConversion coatings are used on metal parts (such as vehicle bodies) to be painted. They are acidic chemical products used before paint to convert the metal substrate to an iron or zinc phosphate surface. The chemical reaction modifies the metal surface to enhance paint adhesion and corrosion protection | |
Conversion FactorUsed to make it easier when converting from one form of ‘measurement' to another. | |
ConversionsTo change one expression to another. For example, expressing miles in kilometres. | |
ConverterAn additive used to provide a chemical reaction to cure paint. Also used with some primers to convert them to 'non-sanding' versions, by changing their properties and making them suitable for wet-on-wet procedures. | |
CoolantLiquid made up of water, anti-freeze and inhibitors used to cool an engine in a sealed but circulated liquid system. | |
COPCoil on plug, where a different ignition coil is used for each spark plug on an engine. Also known as direct ignition. | |
CopperA difficult metal substrate to paint. Also used in the manufacture of special decorative pigments and synthetic driers. | |
Core PlugA steel plate fitted into a cylinder block or cylinder head casting after the casting sand has been removed in order to produce a fully sealed component. | |
CorrosionThe decomposition of a metal in contact with its environment - a chemical reaction of oxygen and moisture or corrosive materials on a metal surface. Also called oxidation or rusting (on ferrous metals). | |
CorrosiveAn acid or other chemical that will chemically react or attack another material. | |
COSHHThe Control of Substances Hazardous to Health Regulations 2002 is a United Kingdom Statutory Instrument that stipulates general requirements on employers to protect employees and other persons from the hazards of substances used at work by risk assessment, control of exposure | |
Cost of productionThe actual cost to the manufacturer of producing a vehicle (it does not include mark-up). | |
Cotter PinTapered pin used to hold shafts into housings. May also be used to describe a split pin. | |
Counter GearSee countershaft assembly. | |
Counter ShaftAn alternative term used to describe the layshaft in a manual gearbox. The shaft in a manual gearbox carrying the gear cluster and meshing with the constant mesh gears. | |
CountershaftAn alternative term used to describe the layshaft in a manual gearbox. The shaft in a manual gearbox carrying the gear cluster and meshing with the constant mesh gears. | |
CountersteerSteering force that acts such as to prevent the wheels moving off their intended line. | |
CoupleA pair of equal parallel forces that are opposite in direction. The effect of a couple is to produce or prevent the turning of a body. | |
Coupling PointThe point or speed at which a torque converter takes up drive. | |
Courtesy LightsLights for the vehicle occupants to use. | |
CoverageThe amount of area a volume of paint will cover at a certain thickness. Theoretical coverage is described as the number of square metres a coating will cover at 1 mm film thickness. | |
CowlingGeneral term used to describe a cover. | |
CPISee single point injection. | |
CPSCrankshaft position and speed sensor. | |
CPUCentral processing unit. This relates to the main component in an ECU or computer. | |
CrackingSplitting of a paint film. Cracking usually appears as straight lines which penetrate the entire film thickness and can be caused by over-baking or by application of excessive film builds. | |
CrankA term used to describe turning the engine by the starter motor. | |
CrankcaseThe part of the engine that houses the crankshaft and the bearings in which it runs. It can be either a separate part or be integral with the engine block. | |
Crankcase VentilationUsually a positive crankcase ventilation (PCV) system that allows any crankcase pressure and oil vapour to be passed into the combustion chamber so that it does not escape into the atmosphere as a pollutant. Early crankcase ventilation consisted of an open vent or breather tube that allowed crankcase gases to be passed out below the vehicle. | |
CrankedDescription of making the engine rotate on the starter motor. | |
CrankingThe process of turning over an engine using a starter motor (or a handle on earlier models!). | |
CrankshaftMajor rotary component of engine that converts piston movement into rotary movement. | |
Crankshaft DamperUsually part of the front pulley. A rubber mounted mass reduced torsional vibration. | |
Crankshaft Oil SealUsually radial lip type seals at the front and rear of the crankshaft. | |
Crankshaft PulleyMain drive pulley on the end of the crankshaft. | |
Crankshaft ShellSee Shell Bearings. | |
Crankshaft WebCounterbalance weights that are opposite the big end bearing journals. | |
Cratering (silicone cratering, see'Fish Eyes')">Small round depressions in a paint film which may or may not expose the underlying surface. Frequently caused by contamination of the substrate by wax, oils, etc. | |
CrawlingThe tendency of a wet paint film to recede from certain areas of a painted surface. Often caused by the presence of contaminants on the surface. | |
CrazingThe formation of surface cracks, often as a fine network, which do not penetrate to the underlying surface of a paint film. Crazing is sometimes caused by the softening effect of solvents from excessive paint coats as in cellulose or acrylic lacquer repair operations. | |
CRCA cyclic redundancy check is a method of checking for errors in data that has been transmitted on a communications link. | |
Crescent PumpA positive displacement pump made from one externally and one internally toothed gear rotating eccentrically in a housing. Inside the housing, and in the space formed where the teeth are out of mesh, is a crescent shaped block. This divides the gear teeth to create the pumping and carrying chambers of the pump. | |
CrimpAct of squeezing a connection such as a terminal onto a wire. | |
Crimped JointTermination of cables by squashing tabs on the terminal around the cable. | |
CrimpingThe process of compressing materials to make a join. Usually refers to squeezing a terminal to secure it to a wire. | |
Crocodile ClipHand operated clip that, like a crocodile, bites under spring pressure to make a contact. Also alligator clip. | |
Cross MemberA chassis or support member that runs across a vehicle frame or chassis. | |
Cross-Coat (double-header)A method of paint application often used with high solids paint. The technique involves a side-to-side application followed by a top-to-bottom application with very little flash-off time. Also used by some refinishers when they apply 'drop coats' in more than one direction to eliminate striping in metallic and pearlescent finishes. | |
Cross-draft BoothA spray booth in which air movement is horizontal from end to end, i.e. fresh (may be heated) air enters at the front of the booth and is extracted at the rear Not considered to be as efficient as downdraught extraction | |
Cross-pin (Hooke's) JointType of universal joint with a cross pin and two yokes. | |
Cross-plyForm of tyre construction in which the casing plies are laid diagonally so that each ply lies at an included angle, usually of more than 40 degrees, to the adjacent ply. | |
Cross-sectionThe area exposed if a cut were to be made through the centre of an object. | |
Cross-shaftsGeneral term used to describe shafts which are fitted across units rather than along or axially. | |
Crown WheelBevel gear wheel in which the teeth are set around the periphery, giving the wheel the appearance of a crown. The larger wheel of the crown wheel and pinion bevel pair. | |
Cruise ControlA system that keeps the vehicle at a set speed. | |
CruisingDriving at a constant speed under light throttle conditions. | |
Crumple ZoneSafety feature of vehicle body, absorbs impacts. | |
CrystallineThe arrangement or bonding of atoms in solid materials which form during cooling to give regular structural patterns. | |
Crystalline StructureThe arrangement or bonding of atoms in solid materials which form during cooling to give regular structural patterns. | |
CSSACold Start Spark Advance | |
CSSHCold Start Spark Hold | |
CTClosed throttle. | |
CTSCoolant Temperature Sensor | |
CTS SensorAbbreviation for the engine coolant temperature sensor or switch. | |
CTVSChoke Thermal Vacuum Switch | |
CTX TransmissionConstantly Variable TransaXle. | |
Cup SealA hydraulic seal with a lip that contains pressure against the lip but will allow a flow in the opposite direction. Used in the cylinders of brake systems. | |
Curb IdleRotational speed of an engine on no-load and minimum throttle setting. Also tick over and idle. | |
CureThe process, usually a chemical change, by which paint is converted from the liquid to the solid state. | |
Cured PaintPaints that have completed the curing process. Cured paints include all factory-applied paints and refinish paints that have air-dried for more than 30 days. Wax application is recommended only for fully cured paints. | |
CurrentMovement of electrically charged particles. Current flow is measured in Amperes. | |
Current RegulatorAn electrical or electronic device used in generator circuits to control the output current. | |
Current RelayA device that usually incorporates a reed switch. It is activated by current flow through a series winding. | |
Custom PaintingUnique painting, frequently with special effects or designs, normally designed by owner of vehicle and/or the specialist who will be painting the vehicle. | |
CutRefers to both the dissolving of solid material in a solvent and the reducing of the viscosity of a liquid by the addition of a thinner. | |
Cut-offProcess where fuel supply can be stopped, for example when a vehicle is coasting down. | |
CutoffSee Cut-off. | |
CV (Constant Velocity) JointA drive shaft joint that transmits drive through an angle without changes in speed. | |
CV JointA drive shaft joint that transmits drive through an angle without changes in speed. | |
CVRControl Vacuum Regulator | |
CVT (Transmission)Constantly variable transmission that uses two conical drums and a drive belt between them. The effective diameter of each drum is varied hydraulically in order to change the drive ratio. | |
Cylinder (Master)(1) Primary source of pressure in a hydraulic system such as brake or clutch system, containing the piston by which pressure is applied and connected to a source of hydraulic fluid. (2) Primary unit for dispensing hydraulic fluid under pressure in a hydraulic system. | |
Cylinder (Slave)Cylinder and piston that, under hydraulic or pneumatic pressure from a master cylinder, actuates mechanical components. For example, the brakes or a clutch. | |
Cylinder BalanceA test carried out with diagnostic equipment to make sure each cylinder of the engine is working to its full potential. | |
Cylinder BlockThe part of an engine containing the cylinders. The cylinder block may also incorporate the water cooling jackets and provisions for the valve gear. | |
Cylinder BoreThe diameter of the cylinder. | |
Cylinder ChargingProcess of filling a cylinder during the induction stroke. | |
Cylinder HeadEncloses the top of the cylinder block. | |
CylindersCylindrical or tubular chambers in which the pistons of a reciprocating engine or pump are fitted. They are contained in the cylinder block. | |
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DA (Dual Action)Refers to a power sander used for flatting substrates. | |
DA (Dual Action) SanderA machine used for random orbital sanding and buffing. The pad of a DA sander travels in a randomized orbital pattern, rather than taking a simple circular path. DA sanders minimize the swirl marks that commonly result from rotary sanding and greatly reduce the time necessary to produce feather-edges. | |
DampenerA device to reduce oscillations or vibrations. A kind of damper. | |
DamperComponent that reduces the oscillations of a spring in a suspension system. A device that smoothes out fluctuations. | |
DampingThe reduction of oscillations or smoothing out of fluctuations. | |
Damping ChamberAn air space in which a damper flap moves that acts to reduce oscillations. | |
Darlington CircuitTwo transistors connected so that the first switches the second. Used to switch high currents. | |
DashpotA damper used on some variable venturi carburettors. | |
DataIn computer science, data is anything in a form suitable for use with a computer. Data is often distinguished from programs. A program is a set of instructions that detail a task for the computer to perform. In this sense, data is thus everything that is not program code. | |
Data LinkGeneral term for a connection to a scanner or similar diagnostic tool. | |
Data rateThe actual speed at which data is transmitted. | |
Databank linkA connection to an electronic source of data. | |
dBDecibels | |
DCDirect Current | |
DC Brushless MotorA DC Brushless Motor uses a permanent magnet external rotor, three phases of driving coils, one or more Hall effect devices to sense the position of the rotor, and the associated drive electronics. | |
DC Direct CurrentAn electrical current that flows in one direction only. Conventionally from the positive pole to the negative pole. | |
DC-DC converterThis is an electronic circuit which converts a source of direct current (DC) from one voltage level to another. It actually converts DC to AC to a different voltage AC and then back to DC! | |
de Dion suspensionA de Dion suspension uses universal joints at both the wheel hubs and differential, and uses a solid tubular beam to hold the opposite wheels in parallel. Unlike an anti-roll bar, a de Dion tube is not directly connected to the chassis nor is it intended to flex. | |
De-energisedSwitched off - usually refers to a coil or relay. | |
De-ionisedUsed to describe pure, neutral water used for topping up batteries. | |
Dead AxleA non-driving axle. Supports the vehicle and carries freely rotating wheels. | |
Dead centreTop or bottom piston positions in the cylinder when the crankshaft is at 0° or 180° of rotation. | |
DecelerationOpposite of acceleration. Reducing velocity or speed. Slowing down. | |
DecelerometerBrake Meter for recording rate of deceleration during braking for test purposes. | |
DecimalA number system that uses a base of 10. | |
Decimal PlaceThe position of numbers after (to the right of) the decimal point. | |
Deck (Block)The top of the engine block forming the mating face for the cylinder head. | |
Dedicated Test EquipmentEquipment made to work specifically with one system or one manufacturer's vehicle range. | |
Deep SocketSame as a normal socket but longer to allow it to be used on a component such as a spark plug. | |
DefamatoryUntrue and harmful information. | |
DEFIDigital Electronic Fuel Injection | |
DeflectionApplied to springs to indicate the amount of movement away from the original position. | |
DegradationThe gradual or rapid disintegration of a paint film, normally due to weathering. May be simply fading/loss of gloss or can lead to total paint film breakdown | |
DegreasingCleaning a bare or previously painted substrate by removing greases, oils, and other surface contaminants. | |
Degrees of AdvanceRefers to crankshaft rotation degrees as linked to ignition timing. | |
DelaminationThe loss of adhesion between two or more layers of paint, causing material to separate from the painted surface or substrate. | |
Delta Wound StatorAn alternator stator winding with the three-phase coils connected at the ends in order to give a large current output. | |
DensityAn expression of the mass of a substance for a given volume, e.g. water has a density of 1kg per litre | |
Desiccant BagChemical used to absorb moisture. Often used in AC systems to remove moisture from the refrigerant. | |
DetailingCareful, in-depth cleaning and polishing of a vehicle's surface finish and/or interior surfaces. | |
DetentA position holding device consisting of a spring and locking piece that locates in a groove. A locating device for holding sliding gears in mesh in a manual gearbox. | |
DetergentA material intended to assist cleaning. The term is sometimes used to differentiate between soap and other surfactants used for cleaning. | |
DetonationIgnition of fuel in an engine that is too early or too rapid. Produces a knocking or pinking sound. | |
DFSDeceleration Fuel Shutoff | |
DGWDesign Gross Weight – i.e. the maximum gross weight that the vehicle was designed to operate at by the manufacturer. This is normally found on the manufacturer’s plate fixed to the vehicle, or in the case of older or heavier vehicles by a ‘Ministry Plate’. Such plates are not required on all vehicles. | |
DIDirect injection of fuel, usually diesel, into the combustion chamber. | |
Diacetone AlcoholA slow-evaporating solvent for paints. | |
DiagnosticsThe process of determining the fault in a system based on observed or measures symptoms. | |
Dial GaugeA gauge used to indicate lateral movement of a component, on a clock (dial) type display. | |
Dial Test IndicatorA gauge used to indicate lateral movement of a component, on a clock (dial) type display. | |
DiameterThe line that goes through the centre of the circle. | |
DiaphragmFlexible disc or membrane which deflects under pneumatic or hydraulic pressure and, in so doing, imparts linear motion to a centrally-located rod or other form of mechanical actuator, as in an air brake or carburettor. | |
Diaphragm SpringDished clutch spring applying clamping force and disengagement linkage. | |
DictionaryA book containing a list of words in alphabetical order. Each word has information given about it (i.e., the definition). | |
DieTool used to cut an external thread. | |
DielectricUsed in a capacitor as an insulator between the two conductive plates. | |
DieselHeavy fuel oil for diesel engines. Compression ignition engine. | |
Diesel 'Knock'Engine noise produced by very rapid rise in cylinder pressure following injection and ignition of the fuel in a diesel engine. | |
DieselingA condition in a petrol engine when it continues to run after the ignition has been turned off. Also known as running on or run on and usually occurs in a very hot carburettor engine where the fuel cannot be fully shut off. | |
DifferentialRelating to or using a difference. Operating on differences in pressure. Bevel gear set that allows two wheels to rotate at different speeds. | |
Differential Pressure ValveA valve that sets its position depending on the difference between two pressures, for example, two fuel pressures or fuel pressure and manifold pressure. | |
Differential Pressure ValvesValves that operate under the control of TWO external pressures or the difference (differential) between them. | |
Digilal ConvertersSee Digital Converter. | |
DigitA number. | |
DigitalA signal current with either an 'on' or 'off' voltage. Digital instruments which show a numerical value. | |
Digital ConvertersElectronic devices that convert analogue signals to digital or digital signals to analogue. | |
DiluentA liquid which increases the capacity of a solvent for the binder. Diluents cannot dissolve the binder themselves. They are usually used to control viscosity or flash-off times. | |
Dim-dip relayA switching relay that results in a resistor being connected in series with dipped lights when ignition and sidelights are switched on. This safety feature as used on some vehicles – but not all. | |
DiodeAn electronic one way valve with polarity bias manufactured from a semiconductor material. | |
Diode PackA collection of diodes that act as a rectifier. A minimum of six diodes in the pack are needed for a three phase alternator. | |
Dip SwitchA switch used to select main beam or dipped beam headlights. Sometimes called a dimmer switch. | |
Dipped BeamThe lower of the two headlamp beams, dipped to avoid blinding the drivers of oncoming vehicles. | |
DippingTo apply paint to an article by immersing it in a container of the paint and then withdrawing the article and allowing the excess paint to drain from the part. Particularly useful for small parts, such as nuts, bolts, brackets, etc. | |
DipstickA stick used to dip in a fluid and check its level! | |
Direct InjectionDiesel engine design where fuel is injected directly into the cylinder. | |
Dirt NibsSmall specks of foreign material in a dried paint film. They can be usually be removed by careful sanding and polishing. | |
DISDistributorless ignition system that uses an ignition coil or coils directly connected to the spark plugs. The ignition is triggered by the ignition module on signals from the ECM (Engine control module). | |
Disc BrakeBrake in which external friction pads are brought to bear on the faces of a rotor or disc, usually by the clamping action of a caliper. | |
Disc SanderPower sanding tool used for grinding, sanding, and rough polishing of repaired metal areas. | |
Discard DimensionThe lowest safe value for a component before it needs to be replaced. Used for brake components such as drums and rotors. | |
Discharge TimeRefers usually to how long a capacitor will take to release all its stored energy. It can be calculated by multiplying the capacitance by resistance and by five (t = 5CR). | |
DiscolorationChange in colour of paint due to chalking, dirt collection, fading, darkening or tonal changes. | |
DiscriminatoryUnfair or unequal treatment of a person due to their age, sex, disability, race, religion etc. | |
DisengagementThe act of removing a connection between two gears of through a clutch. | |
Disk DrivesThe primary data storage device used by computers. It stores and retrieves data. | |
Dispersion CoatingsA type of paint in which the binder molecules are present as colloidal particles. Characterized by a higher percent sprayable solids than is possible with solution-bases paints. | |
DisplacementThe swept volume of a cylinder between the top and bottom positions of the top of a piston. | |
Displacer UnitA hydraulic suspension component that contains gas under pressure and a fluid. | |
DissolutionMetallic particles from the basecoat surface in the clearcoat. If severe, the effect can alter the tone and exaggerate the metallic appearance. | |
DistilledPurified by evaporation and condensation. | |
DistillingDistillation is a method of separating mixtures based on differences in their boiling points in a liquid mixture. | |
Distinctness of ImageA measurement of the accuracy of a reflection in a paint film, which assists the painter in determining the quality of the surface gloss. | |
DistributorA component in the ignition system that houses the primary circuit switching device and the secondary circuit distribution components. | |
Diverter ValveUsed on air injection systems to control the air feed according to the engine running conditions. Also known as a 'dump valve'. | |
DividerA digital circuit that, for example, reacts to only every second input hence dividing it in two. | |
DLCData link connector for connecting a diagnostic tool to a vehicle's electronic systems. | |
Dog ClutchPegs or similar used to transfer drive rotation from one component to another. | |
Dog DrivesPegs or similar used to transfer drive rotation from one component to another. | |
DOHCDual overhead camshaft. Sometimes double overhead camshaft. | |
Donut CouplingA rubber universal joint shaped like a donut. | |
Double-Cardan Universal JointTwo Hooke's or Cardan type universal joints close coupled to increase the effective angle of turn before inducing vibration. | |
Double-declutchA technique that was necessary before the use of synchromesh mechanisms. During a gear change the clutch is lifted as the gear mechanism moves to neutral, the engine is revved (if changing down), the clutch is now depressed and the new gear selected. | |
DowelA locating pin between two mating components. Can be solid or hollow. | |
Down DraftA carburettor where the choke tube (venturi) is fitted vertically. | |
Downdraft BoothA spray booth in which the air movement is from the ceiling (input air) through the floor (extracted air). | |
Downshift ValveAutomatic transmission valve to give a downshift under specific drive conditions. | |
DPFDiesel Particulate Filter | |
Drag LinkSteering linkage between the steering box drop arm (Pitman arm) and the drag arm on the steering swivel. | |
Drain PlugRemovable plug used to let fluid out (engine oil for example). | |
Drain TapA simple valve used to allow a fluid to be removed. | |
Drain TubeA tube used to, for example, remove moisture from an air conditioning evaporator. | |
DrierA chemical which, when added to an enamel, paint, varnish, or oil, hastens the drying or hardening of the film through evaporation. | |
Drive AxleAn axle that transmits a drive to the wheels. Also known as a live axle. | |
Drive BeltTraditionally called the fan belt. A Vee or multi-vee belt to take drive from the engine to auxiliary components such as an alternator or water pump. | |
Drive FlangeA flange that is used to transmit drive from one component to another. The flange on the end of a propshaft is a good example. | |
Drive GearA toothed wheel to pass drive to another toothed wheel. | |
Drive JointsGeneral term used to describe any joint in a drive system such as a CV or universal joint. | |
Drive LineRotary shafts carrying drive to the wheels. | |
Drive MotorA motor that supplies a driving force. Term usually refers to an electric motor. | |
Drive PinionA small gear that drives another gear. | |
Drive PlateA plate that takes the place of the flywheel on an engine such as to transfer drive to a torque converter. | |
Drive PulleysPulleys that transfer drive from one shaft to another. | |
Drive RatiosRatio between gears. For example 2:1 or 1.3:1. | |
Drive ShaftsOpen shafts carrying the drive from the final drive to the driven wheels. | |
DrivelineTransmission components in the line between the engine and wheels. | |
Driveline Wind-upDescription of how a vehicle in four-wheel drive (with no centre differential) can build up spring tension in its transmission components. This is because the front wheels may rotate at a slightly different speed to the rear wheels. | |
Driven PlaneThe plane (like a flat sheet) through which the drive operates. | |
Driven PlateThe clutch disc that is driven by the pressure plate. | |
DriveshaftsOpen shafts carrying the drive from the final drive to the driven wheels. | |
Driving BeamThe upper of the two headlamp beams. Also main beam and upper beam. | |
Driving ThrustForces generated by the engine and transmission. | |
Drop ArmThe output arm on a steering gearbox. Also known as a Pitman arm. | |
Drop-Coat (Finesse coat)A paint application method recommended on many Technical Data Sheets to eliminate patchy finishes in metallic and pearlescent basecoats. The atomising air pressure is reduced and the gun is held further from the surface. Providing the spray gun is then moved across the surface at a uniform speed, angle and distance, this technique should result in better orientation of the metallic and mica particles. | |
Dropping ResistorsResistors used to reduce voltage to a component. | |
Drum BrakeBrake in which friction blocks or brake shoes lined with friction material are brought to bear on the periphery of a drum or cylinder. In most vehicle applications the shoes are brought into contact with the inner periphery of the drum. | |
Dry ClutchA friction clutch that runs in an open housing. As distinct from a wet clutch that runs in an oil bath. | |
Dry CoatA paint having a very low solvent content which produces a gritty film appearance. | |
Dry Film ThicknessThe resultant film thickness of a coating after it has reached its final state of drying or curing. Measured in microns. | |
Dry Liner/Dry Sleeve(US: dry sleeve) Hard metal engine cylinder liner or insert that is not exposed to contact with cooling water. | |
Dry SandingA method of abrading the surface by hand or machine without the aid of any water or other lubricant. | |
Dry SpraySprayed paint which loses so much solvent in the air that it becomes too dry to flow out over the surface. This normally occurs when the chosen thinners is too fast for the atmospheric or application conditions. | |
Dry Sump (Oil Pan)An engine lubrication system where the reservoir of lubricating oil is held in an oil tank. The sump (oil pan) below the engine is scavenged with a separate pump for return to the oil tank. As distinct from a wet sump (oil pan) where the reservoir of lubricating oil is kept in an oil pan below the engine. | |
DryingThe change from a liquid to a solid which takes place after a paint is deposited on a surface. This involves both the evaporation of the solvents and any chemical changes that may occur. | |
Drying OilA liquid that will change to a solid under normal atmospheric conditions when spread out in a thin film. | |
DSGDirect shift gearbox | |
DTCDiagnostic Trouble Code | |
DTIDial Test Indicator. | |
Dual Bed ConverterA three way catalytic converter with one stage coated with platinum and palladium and the other with platinum and rhodium. Converts HC and CO to H and CO2 and NOX to N and O. | |
Dual Circuit Brake SystemA brake system that has two independent hydraulic circuits so that one continues to act if the other fails. The split of dual circuits can be front and rear, diagonal, split front and one rear, and two complete circuits. | |
Dual mass flywheelA dual-mass flywheel is used to isolate torsional crankshaft spikes created by diesel engines during the power stroke. Dual mass flywheels separate the mass of the flywheel between the engine and the transmission. This eliminates damage to the transmission components. | |
Dual Master CylinderA brake master cylinder with two separate chambers for a dual circuit hydraulic system. | |
DuctPipe, tube or trunking. | |
DuctilityThe property of a material that allows it to be drawn into wires. | |
DuctingLarge pipes or similar. Usually refers to the air intake system components. | |
Dump ValveSee diverter valve. | |
DurabilityRefers to the retention of gloss and performance properties in a paint film during prolonged use or exposure to sunlight and other atmospheric conditions. | |
Dust ContaminationContamination due to visible dust particles of various sizes and forms which are embedded or form raised spots in the paint coating. | |
Dust-FreeCondition when a new paint film has dried sufficiently that it will no longer allow dust to penetrate and stick to the finish. | |
Duty CycleThe percentage length of time that an actuator or solenoid is energised by an electronic control unit. Refers to the pulse width. | |
DVOMDigital Volt Ohm Meter | |
Dwell AngleThe angle of distributor cam rotation when the contact breaker points are closed. | |
Dwell MeterMeasures the dwell angle. | |
Dwell PeriodThe angle of distributor cam rotation when the contact breaker points are closed. This term is used when the dwell angle is not a fixed value. Used for electronic ignition systems. | |
DynamicA term that indicates components that are in motion. The opposite of static. | |
DynamoMachine converting mechanical energy into electrical energy. DC. | |
DynamometerA measuring device for engine power output. A brake dynamometer measures the output at the engine flywheel to give the term brake horse power (bhp). A rolling road dynamometer measures the output at the vehicle wheels and is used for test and diagnostic purposes. | |
E |
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E.C. (E)European Commission (Executive). | |
E.C.UElectronic Control Unit." | |
E.C.U.Electronic Control Unit. | |
E.M.F.(emf.)Electro Motive Force. | |
E2PROMElectrically Erasable Programmable Read Only Memory | |
EACVElectronic Air Control Valve | |
Early Fuel EvaporationEarly fuel evaporation system using a heater element below a carburettor to heat the intake air and improve atomisation at cold engine speeds. Improves driveability and reduces harmful exhaust emissions. | |
Earth (Ground)The electrical termination for components connected into a vehicle direct current earth return circuit. On mains electricity a safety route for an electrical short circuit used as a means of protecting people or electrical components from electrical overload.(Ground - US term) | |
Earth (Ground) CableThe battery cable connecting the return side of a vehicle circuit to a terminal on the battery where a ground return circuit is used. (Ground - US term). | |
Earth SwitchingUsed to describe a circuit where the switch breaks the earth side of the circuit instead of the supply side. | |
Earth SwitcingSee Earth Switching! | |
EATXElectronically controlled automatic transmission. | |
EBCMElectronic Brake Control Module | |
EBMElectronic Body Module | |
ECAElectronic Control Assembly | |
ECATElectronic Control of Automatic Transmission | |
EccentricOff centre. Usually refers to a rotating component with the operational part rotating about the central axis of the shaft. An example is a round cam offset from the shaft axis. | |
ECMEngine control module. The electronic control module for engine management systems. | |
ECTEngine coolant temperature sensor or sender. | |
ECUElectronic Control Unit. | |
EDCElectronic Diesel Control. | |
Edge-to-edgePainting technique where full panels are sprayed without blending into masked off adjacent panelwork, or where panels are removed from the vehicle to be painted | |
EDISElectronic distributor or distributorless ignition system. | |
EDPExplanation Demonstration Participation – a reminder of a good way to teach something practical to somebody. | |
EECElectronic engine control module. | |
EEPROMElectronically Erasable Programmable Read Only Memory | |
EFCElectronic Fuel Control | |
EFCAElectronic Fuel Control Assembly | |
EFEEarly fuel evaporation system using a heater element below a carburettor to heat the intake air and improve atomisation at cold engine speeds. Improves driveability and reduces harmful exhaust emissions. | |
EfficiencyA measure of effectiveness given as a ratio, percentage or decimal value (co-efficient) based on actual and possible performance. | |
Efficiency (energy)Energy conversion efficiency is the ratio between the useful output of an energy conversion machine and the input, in energy terms. The useful output may be electric power, mechanical work, or heat. | |
EfficientTo produce work without wasting time and energy. | |
EffortA force or action that tries to achieve something. | |
EFIElectronic fuel injection using sensors, an electronic control unit and fuel injectors to spray fuel into a central throttle body or the inlet ports. Provides very close control of fuel mixture under all operating conditions. | |
EGOExhaust Gas Oxygen Sensor. Also HEGO - Heated Exhaust Gas Oxygen Sensor, EOS Exhaust Oxygen Sensor and Lambda sensor. Provides information to the fuel system ECU on the oxygen content in the exhaust gas. | |
EGRExhaust gas recirculation. An emission control system that uses an exhaust gas feed into the intake air stream to reduce the mass of oxygen in the air charge and limit the formation of harmful oxides. | |
EGRPSEGR Valve Position Sensor | |
EGRTEGR Temperature | |
EIElectronic Ignition | |
Elastic LimitAmount of deflection in a spring that can be tolerated before permanent deformation occurs. | |
ElasticityThe property of materials that can deform and return to their original shape without permanent deformation. | |
Electric FieldArea round an electric charge in which an electric force is exerted. | |
Electrical EnergyThe potential of electricity to do work. | |
Electro Motive Force (e.m.f.)Voltage or pressure in a circuit. | |
Electro Motive Force (emf.)Electrical energy available to a circuit at the battery or generator. | |
Electro PlatingCoating with chromium, silver, etc. by electrolysis. | |
Electro-coating (Electrophoretic coating)Electro-coating is an organic coating method that uses electrical current to deposit paint onto vehicle bodies, part, or other assembled products. | |
ElectrodeUsually a metallic conductor which conducts electricity into a liquid, a gas, a vacuum or on to the surface of a solid. | |
ElectrodepositionA method by which paint is applied electrically by immersing electrodes and the work to be painted in a water-based paint and applying a direct electrical current to them. | |
ElectrohydraulicA combination of electrical and hydraulic control systems. | |
ElectroluminescenceElectroluminescence (EL) is an optical and electrical phenomenon in which a material emits light in response to an electric current passed through it, or to a strong electric field. It is used on in car entertainment systems and instruments on some vehicles. | |
ElectrolyteA liquid that conducts electricity. Battery acid is a good example. | |
ElectromagnetA magnet formed by a soft iron core and an electrical winding about the core. Becomes a magnet when an electrical current flows through the windings. | |
ElectromagneticSee electromagnet. | |
Electromagnetic OscillationChanges from one value to another in a circuit. Usually produces a sine wave output or similar. | |
Electromagnetic SolenoidA solenoid (coil of wire) that is used to operate an actuator such as a fuel injection. | |
Electromagnetic ValveA valve that is operated by a coil of wire, which becomes magnetic when switched on. | |
ElectronElectrons form the outer shell layers of atoms and orbit the protons and neutrons in the nucleus. The electrons have negative polarity and are electrically negative in opposition to the positive charge of the protons. | |
Electron ShellTerm used to describe the orbit of electrons round a nucleus. | |
ElectronicElectrical systems operated or controlled by semi-conductor devices. | |
Electronic ControlSystem usually based round an electronic control unit where the operation of the system is pre-programmed. | |
Electronic IgnitionPetrol ignition system in which switching semi-conductors make and break the low tension circuit. | |
ElectrostaticDescribes the electrical state of something as in static (not flowing) electricity. | |
ElementThe basic form of a material. | |
Electronic Mail. Messages sent from one person to another electronically via a computer. | |
EMCElectromagnetic compatibility. EMC requirements stipulate that a device shall not cause interference within itself or in other devices, or be susceptible to interference from other devices. | |
Emergency BrakeA legal requirement for all vehicles provided by a split hydraulic circuit or a mechanically operated parking brake. | |
Emery PaperCarborundum grit on a backing sheet. | |
EMIElectromagnetic Interference | |
Emission ControlSystems on the vehicle to control (limit) toxic emission. | |
Emission-controlSystems on the vehicle to control (limit) toxic emission. | |
EmitterTerminal of a transistor that becomes conductive when the base is energised. | |
EmoticonsA way of expressing emotions in online communication. E.g., :-) | |
EMRElectronic Module Retard | |
EmulsionA suspension of fine particles in a liquid. The dispersed particles may be binder, pigments, or other ingredients. | |
Emulsion TubeCombined main and compensating jet tubes in a carburettor with provision for drawing air into the fuel flow to create an emulsion at higher engine speeds, thus preventing over-richness and improving fuel distribution. | |
ENEN European Standard e.g. BS EN 50342-2:2007 relates to: Lead-acid starter batteries and is a combined British and European standard (Dimensions of batteries and marking of terminals) | |
EnamelA paint type which forms a film by absorbing oxygen during curing. Characterised by slow drying and having a highly glossy, finished appearance without polishing. | |
End FloatLongitudinal play in shaft, intentional or otherwise. | |
End PlayAlternative term for end float. Longitudinal play in shaft, intentional or otherwise. | |
EnergyAn ability to perform work. SI unit is the 'Joule'. | |
EngagementThe act of making a connection between two gears of through a clutch. | |
Engaging PinA simple pin used to make a drive connection. | |
Engaging PlungerGeneral term to describe a plunger that engages something! Often part of a gearbox. | |
Engine AnalyserComplex test equipment used to check a variety of engine operating functions and conditions. An oscilloscope is usually included. | |
Engine AnalyzerComplex test equipment used to check a variety of engine operating functions and conditions. An oscilloscope is usually included. | |
Engine BlockMain part of the engine that contains the cylinders. | |
Engine CompartmentThe space under the bonnet! | |
Engine LoadHow hard the engine is having to work. For example, accelerating uphill creates a high load. | |
Engine ManagementGeneral term used to describe the control of engine operating functions such as ignition and fuelling. Usually related to electronic control. | |
Engine MapA three dimensional map held in a microprocessor that provides an optimum set of values for the control of ignition timing, ignition dwell period and fuel quantities for all engine operating conditions. | |
Engine Speed SensorProvides information on engine speed to engine management systems (transducer). | |
Engine Support BeamsA bar that is used to support an engine, for example, after the transmission has been removed. | |
Engine Temp. SensorEngine temperature sender unit for temperature gauge and engine management systems (thermistor). | |
Engine TorqueThe amount of turning force produced by an engine. Usually quoted at a set speed. | |
EnrichmentProcess of increasing the mixture strength / reducing the air fuel ratio. | |
EOBDEuropean Onboard Diagnostics | |
EOSEOS Exhaust Oxygen Sensor. Provides information to the fuel system ECU on the oxygen content in the exhaust gas. Also EGO Exhaust Gas Oxygen Sensor, HEGO Heated Exhaust Gas Oxygen Sensor and Lambda sensor. | |
EPAEnvironmental Protection Agency | |
Epicyclic GearSee Epicyclical Gearing. | |
Epicyclical GearingA gear system, consisting in basic form of an internally toothed annulus or ring gear and a central externally toothed sun wheel, with usually three or four planet wheels or gears meshing with the sun wheel and annulus. The planet wheels are often carried as a unit on a planet carrier or spider. Holding the rotation of the planet carrier, annulus or sun wheel will provide a transmission ratio between the two remaining elements. Planetary gear sets can be coupled to increase the available number of ratios. | |
EpitrochoidAn epitrochoid is a shape traced by a point attached to a circle of radius r rolling around the outside of a fixed circle of radius R, where the point is a distance d from the centre of the exterior circle. It is the shape of the cylinder in a Wankel engine. | |
EPOSEGR Valve Position Sensor | |
EpoxyA type of paint, adhesive or plastic noted for high mechanical strength, good adhesion and excellent chemical resistance. | |
EPROMErasable Programmable Read Only Memory. | |
EPTExhaust Electronic Pressure Transducer. | |
ESCElectronic Spark Control | |
ESTElectronic Spark Timing | |
EsterA type of organic compound used as active solvents. | |
EstimateAn opinion or judgement. | |
ETEmergency Testing – the process by which testing may continue when the computerised system is not available due to a wide scale failure affecting a significant number of VTSs. | |
Etch PrimerPrimer with an acid (usually Phosphoric) content. The purpose of the Etch primer in a coating system is to improve the adhesion and corrosion performance of the undercoat system. Their use is recommended when working with ferrous substrates, and essential on non-ferrous substrates | |
EtchingThe process of a strong chemical cutting into unprotected parts of a metal. | |
EthanolEthyl-alcohol produced from starches and sugar plants and used as an octane enhancer. | |
Ethyl AcetateA fast evaporating ester solvent. | |
Ethyl AlcoholAn inexpensive, fast evaporating solvent or diluent. | |
Ethylene GlycolAnti-freeze. Chemical used to lower freezing point of coolant. | |
EUThe European Union (EU) is an economic and political union of 27 (as at 2010) member states, located primarily in Europe. Committed to regional integration, the EU was established by the Treaty of Maastricht on 1 November 1993. | |
Evaluation CircuitAn electronic circuit used to decide a course of action. | |
EVAPEmission control system that uses a charcoal canister to prevent fuel tank vapours from venting to the atmosphere. The vapours are drawn into the engine during specific running conditions to purge the canister. | |
EvaporationThe change from liquid to a gas. When solvents leave a wet paint film, they usually do so by evaporation. | |
Evaporation RateThe speed at which any liquid evaporates. | |
Evaporative CanisterA canister usually containing charcoal that prevents emissions from the fuel tank due to evaporation. | |
EvaporatorA radiator in the air conditioning system fitted in the heater and A/C housing. The refrigerant passes through the pipes in the evaporator and vaporises to absorb heat and therefore cool the air stream flowing into the vehicle passenger compartment. | |
EvidenceThis is what a candidates needs to produce to prove they have the skills required. | |
EVPEGR Valve Position Sensor | |
EVRElectronic vacuum regulator solenoid on EGR system. | |
Excess Pressure ValveA pressure relief valve that opens if pressure exceeds a set value. Often for safety reasons. | |
Exhaust Blow-byGases from the exhaust bypassing a component, for example, the piston rings or a valve in a turbocharger. | |
Exhaust EmissionsSubstances vented into the atmosphere from an exhaust system. | |
Exhaust Gas AnalyserAn instrument for measuring the constituent gases in the exhaust. | |
Exhaust Gas AnalyzerSee Exhaust Gas Analyser. | |
Exhaust Gas RecirculationAn emission control system that uses an exhaust gas feed into the intake air stream to reduce the mass of oxygen in the air charge and limit the formation of harmful oxides. | |
Exhaust ManifoldHeat resisting ducting that connects the exhaust ports of an engine to an exhaust pipe. | |
Exhaust PortsOutlets in the cylinder head for the exhaust after the valve opens. In a two-stroke engine the ports are in the side of the cylinder. | |
Exhaust StrokeThe last stroke of the four stroke cycle when the burnt gases are expelled to the atmosphere. | |
ExpansionAn increase in size. For example, when a metal rod is heated it increases in length and diameter. Opposite of contraction. | |
Expansion BoxOpen muffler in the exhaust system to reduce the noise. | |
Extender PigmentAn inert, usually colourless and semi-transparent pigment used in paints to fortify and lower the price of pigment systems. | |
Extension HousingUsually describes an extra housing on the rear of a transmission gearbox. | |
External assessmentA test set externally to check portfolio evidence. | |
External CustomerOne outside of an organisation. | |
F |
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FFahrenheit | |
F-CANFast CAN | |
F.W.D.Front wheel drive." | |
Face-toneThe colour perceived by the brain when a painted surface is viewed from an angle of 90° - that being the angle at which the greatest amount of light reflection will occur | |
Factory-applied PaintPaint applied to a vehicle at the factory of the original equipment manufacturer (OEM). Factory-applied paint is normally cured by baking. | |
FadingThe gradual loss of colour or gloss of a paint film due to a chemical or physical change, usually due to natural ageing or exposure to harmful environmental conditions | |
Fail SafeA device or feature that prevents total failure in the event of a fault occurring. | |
FallbackThe process by which testing may continue when the computerised system is not available at a VTS, for example, following the breakdown of the VTS device. | |
Fallback ReviewThe process by which test data recorded while testing under Fallback is subsequently confirmed on the MOT computer database. | |
Fan (fan width)The spray pattern of paint as it is emitted from a spray gun. Most spray guns have adjustments that can alter the fan width from a small round pattern to an elongated elliptical pattern. | |
Fan CowlA protective shield around a fan. | |
FaradThe unit of capacitance. | |
Fascia PanelThe panel inside the vehicle below the front windscreen. It carries the instruments, heater ducts and accessories. | |
Fast ChargeRapid charge for a battery. 5 times the Ah capacity for about an hour is the recommended maximum. | |
Fast IdleThe cold engine running speed achieved by a stepped cam on the throttle linkage or by an air bleed valve. | |
FatigueFailure in a material due to excessive and repeated loading usually of an intermittent nature. | |
FaultThe cause of a problem that results in symptoms | |
Fault CodeA code generated in and output from an ECU. Used for diagnostics. | |
Fault-tolerantIn engineering, fault-tolerant design, also known as fail-safe design, is a design that enables a system to continue operation, possibly at a reduced level, rather than failing completely, when some part of the system fails. | |
FBCFeedback Carburettor System | |
FBCAFeedback Carburettor Actuator | |
FCSFuel Control Solenoid | |
FDCFuel Deceleration Valve | |
Feather-edge SplittingFractures or cracks along the feather-edge which occur during drying or shortly after the topcoat has been applied over primer-surfacer. This problem occurs due to poor preparation, use of excessively fast solvents in primer, improper flash-off time and/or very aggressive solvents in topcoat. | |
Feather-edgingTapering a paint edge from substrate to topcoat or between layers of paint material by sanding. If feather-edging has been carried out efficiently, it should not be possible to feel the edges with the finger tips. | |
FeatheringTerm used to describe the way a tyre wears when the tracking is set incorrectly. The tread scuffs up like feathers. | |
Feed (leather)The process of treating leather with soaps and creams to improves its lifespan and appearance. | |
Feed CableThe main supply wire to a component. | |
FeedbackA feature used in electronic control systems to monitor performance by the use of a sensor downstream of an actuator. An example is an exhaust oxygen sensor monitoring the fuel injection quantities. | |
Feedback ResistorA variable resistor used to indicate position of a moving component. | |
Feeler GaugeSet of accurate blades used to set or measure small gaps (valve clearances for example). | |
FerritesThese are chemical compounds, ceramic with iron oxide as their main components. Many of them are magnetic materials and they are used to make permanent magnets, ferrite cores for transformers, and in various other high tech applications. | |
FerrousDescribes any metal composed of or containing iron, such as low-carbon steel, stainless steel, etc. | |
FIFuel Injection | |
FibreglassVery fine fibres of glass that are supplied as reels of single fibres or spun together as woven matting. It is used in the manufacture of glass-reinforced vehicle bodies, panels, and for component parts and repairs on automobile bodies. | |
Field (Magnetic)A magnetic flux about a permanent magnet or live electrical conductor. | |
Field CircuitAn electrical control circuit for the field coils used to regulate the output from a generator. | |
Field CoilAn electrical winding round a magnet pole shoe that is used to create a magnetic field when an electrical current flows through the windings. The direction of current flow determines the polarity of the magnetic pole. Used in generators and electrical motors. | |
Field Coil (Winding)An electrical winding round a magnet pole shoe that is used to create a magnetic field when an electrical current flows through the windings. The direction of current flow determines the polarity of the magnetic pole. Used in generators and electrical motors. | |
Filament (Bulb)The tungsten element in a bulb that glows to produce light. | |
FilamentsThe tungsten elements in a bulb that glow to produce light. | |
Filiform Corrosion (Spidering)A paint defect caused by moisture ingress between the substrate and the paint film, e.g. via an untreated stone chip, that continues to travel in 'spidery' threads. | |
FillerCommonly, a heavily pigmented sprayed foundation paint used to fill imperfections and pores in a substrate. To avoid confusion with 'Body Filler', should be referred to as 'Primer-Filler' or 'High-Build Filler' | |
Filler NeckThe connection into the fuel tank for refuelling. | |
Fillet RadiusA machined curve between two faces of a component. An example is the curve between a crankshaft web and journal. | |
FilmA very thin continuous sheet of material. Paint forms a film on the surface to which it is applied. | |
Film ThicknessThe thickness or depth of a dry paint film is important. Thin films may appear to be the wrong colour due to their lower opacity, and may also have durability issues. Over-thick films are likely to crack in use. The thickness of paint films on iron or steel surfaces is easily determined with a magnetic gauge. | |
Film Thickness GaugeA device used to measure the coating thickness on a substrate. Magnetic devices are used to measure the thickness of ferrous metals; whereas electronic devices are used on non-ferrous substrates. | |
FilterA fine mesh or paper screen used to remove dirt and other contaminants from a liquid or gas (air). | |
Final DriveThe gearing immediately before the driven wheels. It provides a split to each driven wheel with a final gear reduction for the transmission. Can also be used to turn the drive through 90° with the use of bevel gears. | |
Finesse coatSee 'Drop coat' | |
FinishA protective coating of paint; usually referring to the final appearance of the painted surface. Also, to apply a paint or paint system. | |
Finishing FilmA fine graded abrasive disc for sanding top coat automotive paints before repainting or compounding. | |
FirewallSubstantial structural panel of vehicle body in front of passenger compartment. Also known as a bulkhead. | |
Firing OrderThe sequence for ignition of individual cylinders in an engine. | |
Fish EyesA surface depression or crater in the wet paint film. Fish Eyes are caused by repulsion of the wet paint by a surface contaminant such as oil or silicone. The depression may or may not reveal the surface under the paint, depending on its depth or severity. | |
Fish-Eye EliminatorAdditive used in paint to prevent the occurrence of fish eyes (craters/silicones) in a freshly painted surface - usually caused by the presence of contaminants such as wax polish. | |
Fixed CaliperA disc brake caliper in which the two halves and pistons are made as a single unit attached to the axle assembly. | |
Fixed Choke CarburettorA carburettor with a fixed diameter venturi (choke tube). | |
Fixed VenturiA narrowed section in a carburettor - the size of which remains fixed. | |
FlakeA decorative pigment consisting of flat particles. Usually mica, aluminium or other bright metals, providing special colour effects to the final paint finish. | |
Flake OrientationThe appearance of the metallic particles in a paint film during and after drying or curing. Selection of the correct flakes in the colour mixing formula and proper application will lead to good flake orientation and thus to good colour match and appearance. | |
FlakingA serious paint defect characterised by the paint film lifting and eventually falling off of the substrate. | |
Flame PlugCold start device fitted in the inlet manifold on some direct injection diesel engines. | |
Flame TrapIncorporated into the air cleaner unit to prevent the spread of fire caused by fuel igniting in the carburettor if blow back occurs. | |
FlangeFlat face to flat face butted fitting. Method used to secure exhaust system. | |
Flange BoltsBolts that secure a flat face to flat face butted fitting. | |
Flange FittingFlat face to flat face butted fitting. Method used to secure exhaust system. | |
Flare JointA method of connecting pipes, particularly steel brake pipes, where the end of the pipe is deformed to give a concave or convex flare which is secured with a union nut. | |
Flash RustingA surface rust occurring from improper cleaning or exposing bare metal to the air and moisture for too long of a period. | |
Flash-offThe first stage of paint drying where some of the solvent content evaporates. This typically dulls the surface from an exceedingly high gloss to a normal gloss or flat appearance. | |
Flash-off TimeThe time between paint application and consecutive coats. | |
FlashpointThe temperature at which a liquid will give off a flammable vapour that would ignite when a spark is struck. | |
Flat (finish)Lacking in gloss. (See Matting agent) | |
Flat Seat ValveA valve that operates by one part operating against a flat component to control flow. | |
Flat SpotA temporary drop in power that occurs at the point of initial acceleration when the throttle plate is opened. Occurs as a result of a rise in venturi pressure (drop in vacuum) and a resultant loss of fuel supply into the venturi. Remedied by the addition of an accelerator pump. | |
Flat-seat ValveA valve that operates by one part operating against a flat component to control flow. | |
FlattingThe rubbing down of repaired or pre-painted surfaces with abrasives to achieve the desired shape, prepare the surface for painting or prior to polishing. | |
Flex PlateThe mounting plate for a torque converter where it is attached to the crankshaft. Fits in place of the flywheel. | |
FlexibleBeing able to accept change. | |
Flexible AdditiveA substance added to paint to improve its performance characteristics, such as impact resistance, flexibility, and elasticity when applied to plastic or flexible substrates. | |
Flexible CouplingA rubber or fabric reinforced rubber coupling that is used to join two shafts. Usually incorporates two forks that act as a safety device in the event of failure of the rubber component. | |
FlexingAnother word for bending. | |
FlipThe change in value, hue, and chroma of a metallic or pearl car finish when it is viewed from different angles. | |
Flip-toneThe colour perceived by the brain when a painted surface is viewed from an acute angle (i.e. less than 90°). - the more acute the angle, the less amount of light reflection occurs, giving an impression that the colour is darker | |
FlitchA longitudinal cut | |
Flitch PanelStructural panel of vehicle body on sides of engine. | |
FloatA buoyant component used to indicate or control fluid levels. In a carburettor used with a needle valve to control the petrol level in the float chamber. | |
Float ChamberPart of carburettor holding petrol at a controlled level. | |
FloatingThe tendency of pigment particles in a wet paint film to separate from one another and concentrate in particular areas, resulting in a 'patchy' finish | |
Floating CaliperA disc brake caliper that has a fixed component attached to the axle assembly and a single piston and caliper that is 'floating' by sliding or pivoting on the fixed component. | |
FlocculationClumping together of pigment particles within the wet paint. | |
FloodingThe tendency of pigment particles to rise to the surface during curing and produce a colour variation at the surface and a lack of uniformity in the colour appearance through the film. | |
Floppy DiskA portable disk that stores 1.44Mb of information. | |
FlowThe levelling characteristics of a wet paint film. | |
Flow MeterA sensor that determines flow of a fluid or gas. | |
FLSFluid Level Sensor | |
Fluid CouplingA drive coupling that uses a fluid to transmit drive. Also sometimes a viscous coupling. | |
Fluid FlywheelA drive coupling that uses a fluid to transmit drive. | |
Fluid NeedleThe part of a spray gun that opens and closes the fluid passage in the fluid tip. | |
Fluid PumpA pump for moving or pressurising a fluid. | |
Fluid TipPart of a spray gun that meters and directs the fluid stream. | |
FlyweightsWeights that act on pivots and move outwards due to centrifugal force. | |
Flywheel(1) Component of the clutch. (2) Massive wheel or disc attached, for example, to the crankshaft of an engine, to store energy of rotation and smooth the output from the irregular firing of the cylinders. In many automotive engines, the flywheel incorporates the ring-gear and acts as one friction face of the clutch. (3) Maintains the momentum of the engine. | |
FOFuel Octane Adjustment. | |
FoamingA term used to describe the aeration of an oil. | |
Focal LengthThe distance between the focal point and the reflector. | |
Focal PointThe point within a reflector from where a light source produces parallel beams. | |
FocussedTo the point. | |
Follower (Cam)The component in contact with the cam on a camshaft. | |
Foot PoundOld unit of torque. Also pounds/feet. Torque is now given in the SI units of Newton metres (Nm). | |
FootprintWhen applied to tyres describes the area and shape of the part of the tyre in contact with the road. | |
ForceExerted to overcome a load. | |
Force RatioThe comparison of the force applied to the force produced via some kind of machine or system. | |
Force-DryA method of accelerating the drying of paint with the aid of heat. | |
ForgingA component forming process applied to hot metal with a hammer or die either by hand or machine. Also hot stamping. | |
ForkPart of the door latch mechanism, clutch or gearbox. Fits around another component to hold or move that component. | |
Fossil fuelThis relates to any fuel made from hydrocarbon deposits such as coal, petroleum, natural gas and, to some extent, peat; these fuels are irreplaceable, and their burning generates the greenhouse gas carbon dioxide. | |
Four Stroke CycleThe conventional operating principle for the modern internal combustion engine consisting of the induction, compression, combustion/power and exhaust strokes. | |
Four Wheel Drive (4WD) (4x4)Transmission system that uses all four wheels of a vehicle to provide a drive. This term is usually used on vehicles with selectable four wheel drive. The term AWD for all wheel drive is used for vehicles with permanent four wheel drive. | |
Four Wheel Steering (4WS)A steering system that applies turning movement to front and rear wheels. The rear wheel steer is initially opposite to the front wheels, neutral and then with the front wheels. This provides steering characteristics that aid manoeuvrability. | |
Four Wheel Steering 4WSA steering system that applies turning movement to front and rear wheels. The rear wheel steer is initially opposite to the front wheels, neutral and then with the front wheels. This provides steering characteristics that aid manoeuvrability. | |
FPFuel Pump. | |
FPRFuel Pump Relay. | |
FractionsA number of parts out of another number of parts. | |
FranchiseThis is an authorization to sell a company's goods or services in a particular place. | |
Free ElectronsThe electrons in the valency shell of an atom that can link with and move on from other atoms. A material with free electron flow makes a good electrical or heat conductor. | |
Free PlayThe amount of free movement in or between components that is not transmitted to the next component in the sequence. May also be referred to as 'backlash' in some applications such as when applied to gears. | |
Free TravelThe free play in a clutch linkage before it operates the clutch mechanism. | |
FreeplayThe amount of free movement in or between components that is not transmitted to the next component in the sequence. May also be referred to as 'backlash' in some applications such as when applied to gears. | |
FreewheelingOverrun of a one way clutch. Vehicle movement when the transmission is not engaged to the engine. | |
FrequencyThe number of oscillations per unit of time. Examples are a sound wave or alternating electrical current. The unit for frequency is the Hertz, which equals one oscillation per second. | |
FrictionResistance a body encounters in moving over another. | |
Friction DiscTerm used to refer to a clutch drive plate. | |
Friction DiscsComponent of the clutch. The centre plate that is gripped between the flywheel and pressure plate to transmit a drive to the gearbox input shaft. | |
Friction MaterialA material with consistent performance characteristics used to provide a rubbing surface for brake and clutch components. | |
Friction PlateComponent of the clutch. The centre plate that is gripped between the flywheel and pressure plate to transmit a drive to the gearbox input shaft. | |
Front-end SolventA fast-evaporating solvent that leaves the paint very soon after application. | |
FTFuel Temperature Sensor. | |
ft.lbFoot Pound" | |
Fuel DistributorThe component in a mechanical injection system that controls and distributes the fuel. | |
Fuel EfficiencyPerformance of engine/vehicle. Rate of fuel usage. | |
Fuel FilterA filter to remove contamination from fuel. | |
Fuel Gauge SenderSensor, usually a variable resistor, which supplies information on fuel quantity in the tank. | |
Fuel InjectionThe injection of fuel under pressure into the intake air stream of petrol engines by the use of electrical solenoid valves in place of a carburettor. | |
Fuel LineThe pipes and hoses that connect the fuel system components. | |
Fuel Pressure RegulatorIn a fuel system the component that keeps the pressure across injectors constant. It consists of a valve, diaphragm and spring. | |
Fuel RailA tube or pipe used to supply fuel to electrical injectors. The quantity of fuel in the rail is relatively large so that the pressure remains constant when the injectors operate. | |
FulcrumA pivot for a lever. Usually a supporting point or shaft. | |
Fulcrum RingA ring on which clutch release fingers pivot. | |
Full Flow LubricationAn engine lubrication system where all of the oil flows through the oil filter before entering the engine oil galleries. | |
Full LoadDescribes the engine condition when it is working as hard as it is able - for acceleration for example. | |
Full Load EnrichmentA device in a carburettor that provides additional fuel during full throttle and heavy load conditions. | |
Full Wave RectificationAlternating current converted to direct current by reverse flow of the negative bias so that it is added to the forward bias electrical flow. Modern rectifiers using a diode bridge achieve full wave rectification. | |
Fully Floating AxleAn axle hub arrangement that carries the load on two bearings and therefore does not apply a shear or bending force on the axle shaft. | |
FuseA safety device in an electrical circuit that will burn and melt to break the circuit when an excess current is applied. | |
Fuse BoxA central termination block in a vehicle electrical system that carries the fuses. | |
Fuse RatingThe rated value of a fuse before failure due to an excess current load. The rating can be either a constant or a surge value and is given in amps. Fuses are usually colour coded and marked for the fuse rating. | |
Fuzzy LogicA digital control system that makes 'educated' guesses. | |
FWDFront-Wheel Drive | |
G |
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G or gUnit of force equivalent to the force of the Earth's gravity. | |
G-forceA force on an object equivalent to the force applied by the Earth's gravity. | |
G/C ClampA clamp (hand tool) shaped like a G/C. | |
GaiterA rubber (or similar) boot used to cover working components. It is used to keep dirt out and in some cases lubrication in place. Also slang for alligator... | |
galGallon | |
GalleriesSee Main Gallery. | |
GalvanizeA protective process for steel sheet where a thin surface layer of zinc is applied by hot dipping the steel into a bath of molten zinc. | |
Ganged SwitchAn electrical switch that operates two or more circuits from one switching point. | |
GasA fluid state of matter when the atoms are free. The least dense state of matter which can have three states, solid, liquid and gas. | |
Gas AnalyserElectronic equipment that measures exhaust gas constituents. | |
Gas AnalyzerSee Gas Analyser. | |
Gas TurbineA type of internal combustion that uses rotating blades in a compressor to provide charging of the combustion chamber. The output gas pressure is used to drive turbine blades which are connected by a shaft to drive the compressor and a transmission gearbox or in the case of aircraft jet engines to provide air propulsion. | |
GasketA material that is fitted between faces to take up the irregularity of the surface finishes and provide a gas or liquid seal. | |
GasolineA hydrocarbon fuel made up from carbon and hydrogen elements. Used as a fuel for internal combustion engines. Also petrol. | |
GassingThe formation, in the can, of gaseous products in a coating material, due to the reaction between two or more constituents of the coating material or between the latter and the metal of the container. Characterised by a 'Pop' sound when opening paint containers | |
GateIn transmission systems a device to guide a gear into any one position at any one time. In electronics a logic device for regulating electrical current flow according to input voltage levels. | |
GCMGovernor Control Module. | |
GDiGasoline direct injection. Petrol/Gasoline is injected directly into the combustion chamber under high pressure. | |
GearA method of providing leverage. Toothed wheel that meshes with another toothed wheel. | |
Gear BrakePart of an automatic gearbox, the brake is often a band of friction material. | |
Gear ClusterA series of fixed gears on one shaft. Used to provide gear selection by engagement with freely rotating gears on another shaft. The selection is made by locking the freely rotating gear to the shaft. This can be by the use of a sliding hub or a sliding gear splined to the output shaft. | |
Gear ClutchA clutch that connects or disconnects drive to a gear. | |
Gear CogsToothed wheels that mesh with other toothed wheels. | |
Gear LashThe clearance between the teeth of two meshing gears. Also known as backlash when applied to gears. | |
Gear PumpAn oil pump using two meshed gears to provide a positive pumping action. The teeth are of the two gears run in mesh. Where they come out of mesh a small chamber forms to allow oil to flow in, the oil is carried round the periphery of pump in the gear teeth and when the teeth come into mesh the chamber is reduced in size and the oil forced from the pump. | |
Gear RatioRatio of angular velocities of pairs of meshing gears. Number of teeth on driven gear divided by number of teeth on driver gear. | |
Gear ReductionA gear drive that reduces the rotational speed of the output shaft below that of the input shaft. | |
Gear TrainTwo or more gears in mesh that transmit a drive through them. | |
GearboxA housing containing gears to allow different ratios to be selected. | |
Geared DistributorA distributor driven by a gear from the engine. | |
GearshiftThe mechanism for selecting gears in the transmission. Consists of the driver's gear lever, the linkage to the transmission gearbox, and the selectors in the gearbox. | |
GEMGovernor Electronic Module. | |
GENGenerator. | |
GeneratorMachine for converting mechanical energy into electrical energy. | |
GenericA common type or something that is used for a variety of tasks. | |
Gerotor PumpA type of positive displacement oil pump that uses two gears on eccentric axes. One gear is on a shaft inside another rotating in the housing. The pumping and carrying chambers are formed between the gear teeth. | |
GlareReflection from the sun or a light onto the computer screen making it difficult to see properly. | |
GlazeA polish that is safe for use on fresh paints. Some glazes contain a mild abrasive that will remove minor surface imperfections. When a glaze with an abrasive is used, it should be followed by application of wax on cured paint or a hand glaze on fresh paint. A glaze also does not contain silicone. | |
GlazierPerson who works with glass. | |
GlossThe ability of a surface to reflect light. Measured by determining the percentage of light reflected from a surface at certain angles. | |
Gloss MeterAn apparatus for measuring the gloss of paint film. | |
Glow PlugCold start device for diesel engine. Fitted into the combustion chamber and heated by an electrical current so that the injected air and fuel is heated as an aid to ignition when the engine is cold. | |
GNDGround. | |
Popular Search Engine. | |
GovernorA control device that limits the speed of a unit or controls or senses the operation of a unit. An example is the governor in a diesel injection pump which controls the engine speed. | |
Governor PressureThe control pressure in an automatic transmission that senses vehicle speed. It is applied to the hydraulic control unit or valve body to effect gear shifts in relation to vehicle speed. | |
Governor ValveThe valve in an automatic transmission, which is fitted on the output shaft. The rotational speed acts on a spring-loaded valve to regulate pump pressure. The governor pressure acts on the gear shift control plunger in the valve body. | |
GPMGrams Per Mile | |
GPSGlobal Positioning System: This is a navigational system involving satellites and computers that can determine the latitude and longitude of a receiver on Earth by computing the time difference for signals from different satellites to reach the receiver. | |
Grab (Brake)A braking condition where the brakes lock up when light pedal effort is applied. Caused by brake linings digging into the drum or disc on application. Usually cured by forming a chamfer on the leading edge of the lining. | |
GrammarForming well written, easy to read sentences, paragraphs and documents with the use of punctuation (i.e., full stops, commas etc.). | |
GravelometerA device that propels rocks at a painted substrate to measure the resistance the finish has to rock chips. | |
GravityThe attraction that all masses experience as a force towards the earth - or any other planet for that matter! | |
Gravity-feed GunA spray gun which has the paint container on the top of the gun, allowing the paint to flow into the fluid passage by gravity. | |
GreaseA thick sticky lubricant made from a variety of bases, usually derived from crude oils, and used for bearing and chassis lubrication. | |
Greenhouse gasesGases that are a natural part of the atmosphere. They absorb and re-radiate the sun's warmth, and maintain the Earth's surface temperature at a level necessary to support life. | |
GrindingAbrading painted or unpainted metal surfaces to remove paint/corrosion or prepare the area for filling. | |
GritRefers to the abrasive size used in flatting papers, discs, etc. and is classified using 'P' grades, e.g. P40, P120, P600 and so on. The larger the number, the finer the abrasive | |
GrittyA paint product is said to be gritty when it contains large particles, from insufficient dispersion during mixing or when it contains large hard particles of foreign materials. | |
GrommetA blind grommet is a rubber insert fitted into a hole in a plate to blank off the plate. Other types are used to provide protection for cables or pipes that pass through a hole. | |
Groove (Tire)A channel cut in the tread of a tire to facilitate the dispersal of road surface water. | |
Groove (Tyre)(1) A channel cut in the tread of a tyre to facilitate the dispersal of road surface water. (2) The machined slot around the piston into which the rings are fitted. | |
Ground (Earth)The electrical termination for components connected into a vehicle direct current ground return circuit. On mains electricity a safety route for an electrical short circuit used as a means of protecting people or electrical components from electrical overload. | |
Ground (Earth) CableThe battery cable connecting the return side of a vehicle circuit to a terminal on the battery where a ground return circuit is used. | |
Ground ClearanceThe dimension under a vehicle which clears any obstacles in the roadway. | |
Ground TestA test to make sure the earth or ground or chassis electrical connection is in good working order. | |
GroundingA safety practice where two objects are interconnected with clamps and bare wire. This equalizes the electrical potential between the objects and helps prevent static sparks that could ignite flammable materials. | |
Gudgeon PinThe piston pin that connects a piston to a connecting rod. Fitted at the little end of the connecting rod. Also wrist pin. | |
GumPetroleum distillate formed during combustion particularly with poor fuel quality. The gum is deposited on cylinder walls and increases the tendency for glazing. | |
Gun BodyThe main part of the spray gun to which all other component parts are attached. | |
GVWGross Vehicle Weight | |
H |
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H.A.S.W.AHealth And Safety at Work Act 1974.(UK)" | |
H20Water | |
Half ShaftsShafts by which power is transmitted from final drive to driven wheels in an enclosed axle. | |
Hall GeneratorAn electronic pulse generator using the Hall effect of a semiconductor to provide information to the ignition amplifier or ECU on engine position and speed. | |
Hall ICIntegrated circuit as part of a Hall sensor. | |
Hall SensorAn electronic pulse generator using the Hall effect of a semiconductor to provide information to the ignition amplifier or ECU on engine position and speed. Also used for sensing road speed etc. | |
HalogenA description of a series of gases such as argon. | |
HandbrakeHand operated parking brake usually with a mechanical linkage. Also forms the reserve or emergency brake on many vehicles. | |
Handbrake CableA cable that operates the brakes when a lever is pulled. | |
Handbrake LinkageCables or rods used to operate the parking/handbrake. | |
Hard DiskA storage device that holds large amounts of data. | |
HardenerA chemical specifically designed to ensure cure of a paint finish, filler, stopper, resin or adhesive. Also, another name for an activator. | |
HardwareThe physical components of a computer system. | |
HardwiredA physical connection between two or more electrical devices. | |
Harmonic BalancerRotating or oscillating engine balance shaft. | |
HarnessThe collection of vehicle cables wound together with an insulation tape. Also known as a 'wiring loom'. | |
HazardousRisky. Potential to harm people or property. | |
HazeThe development of a cloudy area in the paint film or in a clear liquid. | |
HC(1) Hydrocarbon. (2) High compression. | |
Head GasketSeal between cylinder block and cylinder head. | |
Head-onViewing a repaired/re-painted area from an angle that is perpendicular (at 90°) to the car. | |
Head-up DisplayProjection of instruments onto the windscreen so that the road and the instruments can be seen at the same time by the driver. | |
Header TankThe expansion tank at the top of a coolant radiator, which can be part of the radiator or a separate tank. | |
HeadlampVehicle lighting that provides illumination of the road for the driver. Usually consists of switched main and dipped beams. | |
Headway SensorA device usually fitted in the front grill of a vehicle that in conjunction with a transmitter senses distance in front of the vehicle. Often part of an active cruise control system. | |
HeatA form of energy in all materials that can be used to do work. | |
Heat ExchangerA device for transferring heat from one system or place to another. | |
Heat RangeApplies to spark plug construction where the rate of heat loss from the plug nose is controlled by the length of the insulation. Spark plugs are given a rating from hot to cold to classify the heat range and application. The plug tip temperature is controlled to keep the tip and electrodes clean. | |
Heat SinkA plate to which electronic components are attached to dissipate heat. | |
Heater MatrixSmall radiator used to exchange heat from the coolant to the vehicle cabin. | |
HEGOHeated Exhaust Gas Oxygen Sensor. Also EGO Exhaust Gas Oxygen Sensor, EOS Exhaust Oxygen Sensor and Lambda sensor. Provides information to the fuel system ECU on the oxygen content in the exhaust gas. | |
HEIHigh Energy Ignition. A distributor ignition system using electronic control of the coil secondary output. | |
Helical GearA gear with teeth cut at an angle. | |
Helical RotorA turbine or compressor in a turbocharger often has vanes that are helically shaped. | |
Helical SpringMetal spring used in vehicle suspension. Also known as a coil spring. | |
HemisphereA sphere is a perfectly round geometrical object in three-dimensional space, such as the shape of a round ball - a hemisphere is half a sphere | |
HeptaneA fuel used in research tests as a comparison when determining the octane rating of fuels. Octane value of zero. | |
HertzThe number of oscillations per unit of time. The SI unit for frequency is the Hertz which equals one oscillation per second. | |
HexShort for hexagonal. | |
HgMercury | |
Hide MalletSoft hammer made of hide (leather). Plastic types are also used. | |
Hiding or Hiding Power(See 'Opacity') | |
High BoilersSolvents with boiling points above 100 degrees Celsius. | |
High Lift CamA special cam profile used on performance engines to increase the opening size of a valve. | |
High resistanceAn unwanted resistance in a circuit that causes it to operate incorrectly. | |
High SolidsPaints are described as having high solids when they contain more than 50-60% solids. High solids paints have lower VOC's. | |
High TensionThe term used for the high voltage in the secondary circuit of the ignition system. | |
HLGHall generator. A sensor using a Hall effect to provide signals to an ECU. | |
HO2SHeated Oxygen Sensor | |
HoistTo lift something or a term used to describe a vehicle lift or ramp. | |
Hold-in WindingA winding in a starter motor solenoid that holds the switch contacts together and the drive pinion in mesh during engine starting. | |
HoldoutThe ability of a surface to keep the topcoat from sinking in and causing a decrease in appearance or gloss. | |
HomogenousUniform in structure or composition throughout. This is usually used to refer to a fuel air mixture in a cylinder that is a 'perfect' mixture of fuel and air. | |
HoneA light grinding process applied to cylinder bores in preparation for the fitting of new pistons. | |
Hooke's JointA drive shaft universal joint consisting of two yokes and a cross bearing. Also Cardan joint. | |
Horizontally OpposedAn engine configuration where cylinder pairs are fitted on opposite sides of the crankshaft. Sometimes referred to as 'Boxer' engines. | |
HorsepowerA measure of power equivalent to 0.746 Kilowatts. Defined by a rate of doing work of 33,000 foot pounds per minute (550 foot pounds per second). | |
HOS HO2SHeated Oxygen Sensor. | |
Hose ClampSimple ring type clamp to seal a hose onto a pipe. | |
Hot Idle CompensatorA device to change idle or mixture settings when an engine is hot. | |
Hot SprayThe technique of applying paint at elevated temperatures. The elevated temperature reduces the viscosity so that higher solids materials can be sprayed, and allows application with less solvent. | |
Hot StampingA machine forging process using a series of dies to create the completed shape. | |
Hot WireA small thin wire that is heated an placed in an air flow. The change in temperature is used to determine the rate of air flow. | |
hpHorsepower | |
HTHigh Tension | |
HT CablesHigh tension leads (high voltage) used to supply the spark. | |
HT LeadsHigh tension leads (high voltage) used to supply the spark. | |
HubCentre of a wheel or gear or similar. | |
Hub NutMain nut that secures a wheel hub. | |
HueThe quality by which colours are distinguished from one another, such as">a red from yellow, blue, green, or purple, and all shades in between. | |
HuntingUneven running of an engine, usually when the mixture is over rich. | |
HVACHeating, ventilation and air conditioning. | |
HVLP (High Volume, Low Pressure)Describes a paint gun that uses a high volume and low pressure of atomising air to apply material to a surface. This provides high transfer efficiency and lower overspray. | |
HybridA hybrid vehicle is a vehicle that uses two or more power sources to move the vehicle. The term most commonly refers to hybrid electric vehicles (HEVs), which combine an internal combustion engine and one or more electric motors. | |
Hybrid vehicleVehicles that use both a traditional engine (combustion) and a rechargeable system (typically operated by a battery) to improve mileage, cause less pollution, and decrease need for fossil fuel. | |
HydraulicA system for transmitting and modifying force by the use of a liquid. Consists of a pump, control devices, hydraulic lines and slave cylinders. | |
Hydraulic BrakeBrake actuated only by hydraulic pressure. | |
Hydraulic ClutchA clutch, operated by fluid pressure. | |
Hydraulic HosesHoses that carry fluid under high pressure. | |
Hydraulic LiftersHydraulic cam followers in the valve opening mechanism. | |
Hydraulic PedestalSelf-adjusting support for a finger tappet in the valve opening mechanism. | |
Hydraulic PressurePressure applied by a fluid. | |
Hydraulic TappetsSelf-adjusting cam followers in valve opening mechanism. | |
Hydraulic ValvesValves used to control pressure or flow of a hydraulic fluid. | |
HydrocarbonA compound which contains only carbon and hydrogen, which are distillate by-products of petroleum, natural gas and coal. | |
Hydrocarbon (HC)Chemical compound which contains only, or principally, Carbon and Hydrogen. The principal constituent of liquid fossil fuels. | |
Hydrocarbon EmissionsFuel vapours released into the atmosphere from a vehicle exhaust or fuel tank. | |
HydrocrackTo break down (a hydrocarbon) by the process of hydrocracking. This is a catalytic cracking process of breaking down large hydrocarbon molecules into smaller ones | |
HydrolysisReaction with water. Usually refers to a decomposition process leading to paint failure. | |
HydrometerInstrument used for measuring specific gravity/relative density of a liquid (coolant, battery electrolyte). | |
Hydropneumatic SuspensionA suspension system using a liquid to transfer suspension movements to pneumatic (gas) springs. | |
HygrometerInstrument used for measuring relative humidity - in an automotive context it is used to check moisture content of brake fluid. | |
HygroscopicA paint film or other solid that readily absorbs water. | |
Hypoid GearingBevel gear with the axes of the driving and driven shafts at right angles, but not in the same plane, giving some sliding action between teeth. Widely used in rear axle final drives. | |
HysteresisA characteristic of materials, sensors and sometimes instruments to make their behaviour dependent on the immediate history to which they have been subjected. Typically the final settling point is different when approached from above to when it is approached from below | |
I |
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I.F.SIndependent Front Suspension. Also inertia fuel shut off switch used to switch off an electrical fuel pump or diesel fuel pump solenoid when the vehicle is involved in an accident." | |
I.R.SIndependent Rear Suspension." | |
IA ISAIdle adjust. Idle speed adjust. | |
IACIdle Air Control | |
IATIntake air temperature sensor used in electronic fuel injection as a correction factor for the quantity of fuel to be delivered. | |
IATSIntake Air Temperature Sensor | |
ICIntegrated Circuit | |
ICEIn Car Entertainment system. | |
ICMIgnition Control Module. | |
ICSIdle Control Solenoid | |
ICTInformation and Communication Technology. | |
IDInside Diameter | |
IDIIndirect injection of diesel fuel into a pre-combustion or swirl chamber in the cylinder head. | |
IdleTerm used to describe an engine running at a speed when the throttle has not been depressed. Also used to describe a lazy technician... | |
Idle Air Control (IAC)Idle air control. An air valve on fuel injection systems to increase the air flow and idle speed of a cold engine and during warm up. | |
Idle Control ComponentsParts that are designed to keep the engine idle speed at a set level. | |
Idle MixtureThe fuel strength or air/fuel ratio. | |
Idle SpeedRotational speed of an engine on no-load and minimum throttle setting. Also tick over and curb idle. | |
Idler ArmA steering arm parallel to the Pitman arm (drop arm) and connected to it by a centre track rod. | |
Idler Gear(1) A gear between two others that does not affect the gear ratio. Any gearwheel between the driving and driven gears in a gear train, the shaft of which serves only to bear and locate the gear, and is therefore 'idle'. The idler gear may serve to reverse the rotation of the driven wheel, so that it rotates in the same direction as the driving wheel. (2) An intermediate or tensioning pulley for a belt drive. | |
IdlingDescribes an engine running at idle speed (usually 700 to 800 rev/min). | |
IECInternational electrotechnical commission | |
IFIIndirect Fuel Injection | |
IGBTThe insulated gate bipolar transistor or IGBT is a three-terminal power semiconductor device, noted for high efficiency and fast switching. | |
IGNIgnition | |
IgniterThe part of an air bag unit that sets the inflation process in to action. | |
Ignition - IGNStarting of combustion. Setting fire to a flammable substance. In a petrol engine the spark jumping the spark plug electrodes that starts the combustion process. | |
Ignition AdvanceThe automatic bringing forward of the ignition spark in relation to the engine speed. | |
Ignition circuitThe system used to connect components involved in producing a high voltage at the spark plugs. | |
Ignition CoilAn electrical transformer that increases the battery voltage to a high tension capable of arcing across the gap of spark plug electrodes. | |
Ignition Coil - IGCAn electrical transformer that increases the battery voltage to a high tension capable of arcing across the gap of spark plug electrodes. | |
Ignition DistributorA component in the ignition system that houses the primary circuit switching device and the secondary circuit distribution components. | |
Ignition LagA short delay after injection before the fuel ignites. | |
Ignition ModuleThe electronic unit that switches the ignition coil on and off in response to a signal from a pulse generator. | |
Ignition SwitchThe engine ignition and vehicle electrical circuits control switch used by the driver to start and stop the engine. | |
Ignition TimingThe static and dynamic settings of the ignition distributor or in the engine control module (ECM) that control the ignition coil secondary circuit output and spark for starting the combustion process in the engine. | |
IlluminationLighting up, making bright. | |
IMAIntegrated Motor Assist is Honda's term for their hybrid propulsion system. This includes the electric motor/generator, 144v battery pack, controlling electronics and the wiring that connects them all together. ISG or ISA is used by some manufacturers, Integrated Starter Generator or Alternator. | |
ImmediatelyTaking place without delay. | |
Immiscible (non-miscible)Incapable of mixing in or blending with other components. | |
ImmobiliserUsually part of an alarm system. It cuts off the ignition or fuel to prevent a vehicle from being started and stolen. | |
Impact SwitchA switch that operates when the car impacts something. Used as a safety device to cut off a fuel pump. | |
Impact ToolsPower tools that use a high frequency hammering action for the removal and installation of nuts and bolts, for drilling and chiselling. Impact tools should only be used with sockets, drills and chisels made for that purpose. The use of normal hand tools form impact is hazardous as these may shatter in use. | |
ImpellerVaned disc that creates flow by centrifugal force (water pump). In a torque converter it is driven from the engine to force liquid onto the turbine. | |
ImperialOld British standard of measurement using yards, feet and inches. | |
Imperial MeasurementDefined by three measures - the gallon, the yard and the pound. | |
In-line EngineA engine fitted along the axis of a motor vehicle. | |
Inboard BrakesBrake units fitted on the final drive casing and output shafts rather than on the wheel hub and carrier. | |
IncandescenceLight given off by a high temperature object. Usually describes a bulb filament. | |
Included AngleCamber and steering swivel (king pin) inclinations (angles) added together. | |
Incoming Telephone CallTo receive a telephone call. | |
Independent SuspensionSuspension fitted to each wheel." | |
Indirect InjectionDiesel engine design where fuel is injected into a pre-combustion chamber fitted inside the cylinder head. | |
Induced VoltageNaturally occurring voltage in a conductor when subjected a magnetic flux. | |
InductanceProperty of a coil such that an increase in current causes an increase in magnetism, which in turn tends to prevent the original increase in current. See also Lens's law. | |
Induction1. The drawing in of a gas or fluid. 2. Process of causing an electrical potential in a conductor due to relative movement of a magnetic field. | |
Induction PeriodAn allotted amount of time upon mixing of components for compatibilization. The process is common among the use of epoxy/polyamide coatings. | |
Induction StrokeFirst stroke of four stroke cycle when air and fuel enter the engine as the piston moves down the cylinder. Also known as the intake stroke. | |
Inductive CoilAll coils possess inductance. This is the property that resists changes in current flow. | |
Inductive GeneratorA magnetic/electrical pulse generator used as a sensor in electronic control systems. It uses an iron core and electrical winding to induce an electrical current when passed by a toothed wheel or rotor. Also known as a magnetic pulse generator. | |
Inductive SensorA coil and magnet used in conjunction with a trigger wheel. It produces a sine wave output with a frequency proportional to speed. | |
Industrial FalloutChemical compounds present in the air which are deposited on the horizontal surfaces of vehicles and which may damage the finish. | |
Inert GasA non-reactive gas element. | |
InertiaThe force that holds a body stationary or in uniform motion. | |
Inertia ReelType of seat belt that holds spare webbing on a reel and locks the reel on impact. This is performed by a swinging weighted ball and lever that locks the belt reel ratchet wheel with a pawl. | |
Inertia SwitchA switch that operates by the inertia (need to stay at a constant speed or state of rest) of a mass. Usually used to cut off supply to a fuel pump in case of a crash. | |
InflationThe general increase in the price of goods and services. | |
InfraredLight energy that produces radiated heat, used for speeding up the curing of paint, filler, etc. | |
Infrared LightThat portion of the spectrum responsible for most of the heating effects of the sun's light. Not visible to the human eye. | |
Infrared LightingInfrared light is outside the visible spectrum. When used for lighting, a special detector is also needed. | |
Infrared SensorA sensor that is sensitive and produces a signal in response to infrared light. | |
IngestionTake in by swallowing or absorbing. | |
InhalationBreathing in. | |
InhibitTo hinder or to restrain progress. | |
InhibitorA chemical added to retard or prevent a particular reaction. | |
Inhibitor SwitchA simple switch that prevents the operation of a circuit. A good example is the switch in an automatic transmission gearbox that prevents operation of the starter motor when drive or reverse is engaged. | |
InhibitorsA chemical that restricts or reduces the chemical reactions. In a cooling system an inhibitor is added to prevent corrosion of the engine from the ethylene glycol content of the antifreeze. | |
Initial diagnostic assessmentThis is carried out to find a candidates strengths and weaknesses, current levels of attainment and potential. | |
InitiatorA chemical added to help start a chemical reaction such as polymerization or curing. | |
INJInjector valve. | |
InjectionOf fuel by pressure into inlet manifolds (petrol) or combustion chamber (diesel). | |
Injection LagA short time delay between actuation and actual operation of an injector. | |
Injection TimingPoint within the four-stroke cycle when injection occurs. Similar to ignition timing on petrol engines. | |
InjectorControl valve and nozzle used to inject and atomise fuel. | |
Injector lagA short time delay between actuation and actual operation of an injector. | |
Injector NozzleThe tip of a fuel injector, which is drilled to produce a particular spray pattern. | |
Injector Pulse WidthWhen viewed on an oscilloscope, the horizontal width of the trace. This represents the open time of the injector. | |
Injector PumpFuel pump that produces the timed high pressure pulses for the injection and timing of fuel delivery on a diesel engine. | |
Inlet ManifoldDucting that connects the carburettor/fuel injection components to the inlet ports in the cylinder head. | |
Inlet PortsThe way in to the engine for fuel/air mixture. | |
Inlet ValveValve in the inlet port that allows air or air/fuel mixture into an engine. | |
Inline PumpType of diesel fuel injection pump with the pump elements in line. | |
Inner RacesThe inside rings of ball or roller bearings. | |
Inner TubeThe separate sealed air tube on a tyre that is required with certain types of tyre and wheel rim. | |
Inner WingMetal panel structure under the bonnet forming part of the wing. | |
InputPower or data that goes into a mechanical unit or electronic control module. | |
Input DeviceA device that allows you to put information into the computer. Egg, keyboard, mouse. | |
Input ShaftShaft that takes drive from the engine into the gearbox. | |
Insert (Valve Seat)A steel insert fitted in aluminium and some iron cylinder heads to form a durable seating for the inlet and exhaust valves. | |
InshotA feature of air brakes designed to give an initial quick application to make up for the time it takes for air pressure change. | |
Instrument LightsIllumination for instruments such as the speedometer. | |
Instrument PanelThe panel in a vehicle fascia that holds the instruments and warning lights. Also dash panel and dashboard. | |
Insulated CircuitA vehicle wiring system that does not use the body and chassis as a ground to form a return electrical circuit to the battery and alternator. A separate insulated set of cables connects all components to complete the circuits. Used in vehicles where there is a high fire risk. (Fuel tankers). | |
Insulation resistanceThe resistance to current flow of the insulating materials between circuits and contacts. | |
InsulatorRestricts the flow of electricity or heat through the material. | |
Intake ManifoldSee inlet manifold. | |
Intake StrokeAlternative term for the induction stroke. First stroke of four stroke cycle when air and fuel enter the engine as the piston moves down the cylinder. | |
Integral Body ConstructionModern light vehicle body and chassis construction method which has no separate chassis. The strength is built in by the use of stressed and reinforced panels. | |
IntegrateTo incorporate something into something else or to unite into a whole. | |
Integrated Circuit (IC)An electronic device consisting of transistors, diodes and other components in a single unit and usually having a specific function. | |
IntegrityData corruption refers to errors in computer data that occur during transmission, retrieval, or processing, introducing unintended changes to the original data. Computer storage and transmission systems use a number of measures to provide data integrity, or in other words the lack of errors. | |
Intelligent deviceA component that has some ability to monitor itself and react to changes. | |
IntensifierA device which converts low pressure fluid power into higher pressure fluid power (used by some injection systems) | |
Inter-Quartile MeanThe average of the values in the inter-quartile range. | |
Inter-Quartile RangeThe range of numbers with the upper and lower quartiles removed. | |
InteractiveTwo-way communication. | |
IntercoolerAn air to air radiator type heat exchanger fitted after a turbocharger in the air intake ducting to cool the intake air before it enters the engine. | |
Interference FitThe relationship between the dimensions of two components where one fits inside the other. In this instance the fit is one where the inner dimension of the outer component is less than the outer dimension of the inner component. | |
Interior LightsLights inside a vehicle for illumination purposes. | |
Interleaf FrictionFriction between spring leaves that produces a damping effect. | |
InterlockPart of a manual gearbox selector mechanism that prevents the engagement of two gears at the same time. | |
Intermediate GearAny gear in a transmission gearbox other than top and bottom or reverse. | |
Intermediate ShaftA shaft between the input and output shafts, usually as part of a gearbox. | |
Internal CombustionEngine where fuel is burnt inside cylinders. | |
Internal CustomerOne inside of an organisation. | |
Internal DampingA feature of some suspension components where friction tends to reduce oscillations. | |
Internal ResistanceDescribes the resistance of a component that is the combination of all its internal parts. Even a battery has some resistance inside it. | |
Internal SplinesSplines (teeth) inside a shaft or tube. | |
Internal TaperA hole that narrows. | |
Internal verificationThe process whereby a centre ensures it operates consistently and to national standards in interpreting and assessing the key skills. | |
Internal WindingsWindings inside a component. | |
InternetA worldwide network of computers that allows us to view the World Wide Web. | |
InterpretTo understand and be able to explain something. | |
IntimidatingTo make somebody feel uncomfortable, timid or even fearful. | |
IonAn atom with positive or negative charge due to gain or loss of an electron. | |
IPUIntegrated Power Unit. | |
IridescentsAll colours that contain aluminium, mica, or other particles that impart a metallic appearance to the colour. | |
Irradiation TreatmentA process where something is acted upon by radiation from a radioactive substance - it is used to make some foodstuffs last longer - but is a contentious issue! | |
ISInertia Switch. | |
ISCIdle Speed Control. This term is usually used when a stepper motor or solenoid is used for idle speed increases during engine warm-up and when ancillary systems are in use. | |
ISOInternational Standards Organization | |
Iso-octaneA fuel used in research tests as a comparison when determining the octane rating of fuels. Octane value of 100. | |
IsocyanateA chemical found in the hardening agent used with acrylic urethane and other two component reaction type paints. The introduction of Isocyanates in hardeners led to the requirement for air-fed respirators in the vehicle painting industry | |
ITInformation Technology | |
ITCSIgnition Timing Control System | |
ITSIdle Tracking Switch | |
J |
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JackA mechanical or hydraulic tool for lifting a vehicle. Should always be used with axle stands if under vehicle access is needed. | |
Jack StandsVehicle support equipment manufactured with a rated weight capacity. Used to support a vehicle when wheels are removed or when access to the underside is needed. Also known as axle stands. | |
Jam (Lock) NutA nut that is used to lock another nut or threaded component in position on a threaded rod or stud. Also lock nut - US term. | |
Jamb SwitchSwitch fitted on a door jamb or pillar for operating the courtesy light or vehicle alarm system. | |
JammingThe deliberate radiation or reflection of electromagnetic energy for the purpose of disrupting enemy use of electronic devices or systems. Or informal music creation in a group! | |
JASJet Air System | |
JetA calibrated nozzle in a gas or liquid injection system. In a carburettor used to regulate fuel and air flows. | |
Jet NeedleA small needle that works inside a jet (small hole) to control fuel flow in a carburettor. | |
JigA device for locating and holding a piece of work during machining operations. | |
Jiggle pinMost thermostats have a Jiggle pin. Its function is to allow trapped air past a closed thermostat as a build-up of air in front of the wax capsule could cause engine damage. | |
JounceSuspension bump travel due to the wheel hitting an irregularity in the road surface. Also applies when the suspension is pushed down. Also known as bounce. | |
JournalThe surface hardened cylindrical part of a shaft that forms part of a bearing. The journal rotates in round sleeve or split shell bearings. | |
JoystickA control stick that operates a system. | |
JudderIrregular braking or clutch operation with intermittent snatching. | |
Jump LeadsHeavy duty electrical cables used to connect a slave battery to a vehicle with a discharged battery for starting. Also jumper cables. | |
Jump StartStarting a vehicle engine with the aid of a slave battery and jump leads. | |
Jumper CablesHeavy duty electrical cables used to connect a slave battery to a vehicle with a discharged battery for starting. Also jump leads. | |
K |
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KAMSee Keep Alive Memory. | |
KDSKick Down Switch. | |
KE-JetronicA mechanical injection system from Bosch, but with some electronic control. | |
Keep Alive Memory (KAM)Part of a microprocessor RAM that holds temporary data for a specified duration. The KAM requires a constant voltage to retain data. It is cleared when the power is turned off. | |
KERSA kinetic energy recovery system is an electric generation, storage, and propulsion system used in Formula One (up to 2010 anyway), which generates electricity during slow down, stores energy in batteries or a flywheel, and boosts acceleration with electric drive motors assisting the engine. Many hybrid cars are similar. | |
KeyA locating device that sits in slots on a shaft and pulley or gear wheel. Also known as Woodruff key. | |
Key DataImportant, relevant information. | |
KeyboardThe typewriter-like keys used to input data into a computer. An input device. | |
kHzKilohertz | |
Kick DownA switch of a cable on an automatic transmission signals that the throttle is at least 90% open. Under certain conditions this causes a downshift for improved acceleration. | |
Kick Down SwitchSwitch on an automatic transmission that signals that the throttle is at least 90% open. Under certain conditions causes a downshift for improved acceleration. | |
Kick-outThe precipitation of dissolved binder or additive from solution as a result of solvent incompatibility. | |
KickbackRoad shocks transmitted to the driver through the steering system. | |
Kilowatt1000 watts | |
KineticMovement energy. | |
Kinetic BalanceThe balance of a rotating component about the perpendicular to the axis. Wheel balance has both static and dynamic quantities. | |
Kinetic EnergyEnergy in the form of a mass moving. | |
King Pin AngleAlternative term for KPI (King Pin Inclination). | |
King Pin InclinationThe angle that the king pin axis tilts from the vertical. Used to provide centre point steering where the centre of the tyre tread is on the steering pin axis. | |
King PinsA type of steering swivel fitted to beam axles. | |
KmKilometres | |
KNKKnock signal from an engine knock sensor to the ECM. | |
KnockAdvanced or quick detonation of fuel in a cylinder where the resultant pressure rise causes a shock wave through the piston, crankshaft and engine block. | |
Knock SensorA piezoelectric sensor used to provide sensor signals to an ECM when an engine is knocking. A closed loop control retards the ignition to prevent knock. | |
KnockingUsed to describe engine knock or a noise produced that sounds like one object hitting another. | |
KnowledgeKnowledge is defined by the Oxford English Dictionary as (i) expertise, and skills acquired by a person through experience or education; the theoretical or practical understanding of a subject; (ii) what is known in a particular field or in total; facts and information; or (iii) awareness or familiarity gained by experience of a fact or situation. | |
Knuckle (Steering)Steering stub axle assembly. Also known as a steering swivel. | |
KOEC''Key On, Engine Cranking'' | |
KOEO''Key On, Engine Off'' | |
KOER''Key On, Engine Running'' | |
kPaKilopascals - unit of pressure. | |
KPIKing Pin Inclination or the angle that the king pin axis tilts from the vertical. | |
KSKnock Sensor. | |
KVKilovolts | |
L |
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LLitres | |
LacquerA deposit that builds up in fuel components. It is similar to varnish. | |
LacquersPaints that dry by evaporative loss of solvent, e.g. Cellulose and 1K Acrylics. The film remains soluble in and susceptible to attack by the same or similar solvents. | |
Ladder ChassisA chassis construction consisting of two longitudinal side members and a series of cross members. The finished chassis has the appearance of a ladder. | |
LadenCarrying a load. | |
Lag (Valve)The term applied to valves which remain open after the piston has passed tdc or bdc at the end of a stroke in the four stroke cycle. | |
LambdaGreek letter like an upside down y. It represents the ideal air to fuel ratio of 14.7:1. | |
Lambda SensorProvides information to the fuel system ECU on the oxygen content in the exhaust gas. Also, EGO Exhaust Gas Oxygen Sensor, HEGO Heated Exhaust Gas Oxygen Sensor and EOS Exhaust Oxygen Sensor. | |
LaminatedA layered component made from thin sheets of material. | |
Laminated GlassPlastic or vinyl core with thin glass each side. An approved glass construction for vehicle windscreens. | |
Laminated SpringA leaf spring with multiple leaves. | |
LandThe sliding areas on pistons either side of ring grooves or fluid passages. The area on shafts that an oil seal lip seals against. | |
Lap and Diagonal BeltType of seat belt that has a single belt threaded across the lap and shoulder and anchored at three points. The anchorage points are both sides of the lap and on the pillar above the shoulder of the wearer. Also known as a three point seat belt. | |
Lap BeltType of seat belt that has a lap restraint belt only. | |
Large Class 4A Class 4 vehicle with a DGW greater than 2500kg. | |
Latching RelayA relay that latches into a set position when first operated and then back to its rest position next time it is operated. | |
Latent HeatThe heat energy that is needed to bring about a change of state of a material. During a change of state the temperature remains constant. | |
Lateral ForcesSideways forces. | |
Lateral RunoutMovement from side to side in a rotating component. | |
LaterallySideways to the length of the vehicle. | |
LatexAn emulsion; usually a dispersion of a polymer in water. | |
Layrub JointA type of limited angle constant velocity joint consisting of an enclosed rubber disc with two pairs of sleeves which are attached to mountings on the ends of the shafts. | |
LayshaftThe shaft in a manual gearbox carrying the gear cluster and meshing with the constant mesh gears. Also known as a countershaft. | |
Lazy LockTerm used to describe the automatic closing of windows when central locking is operated. | |
lb. ft.Pound Feet" | |
LCLow Compression. | |
LCDLiquid Crystal Display. An electronic display device using liquid crystals in a glass sandwich. The glass has an inner transparent series of conductors and polarizing filters. Electrical signals to the conductors rearranges the liquid crystals to form digital or other images. | |
Lead (Valve)The term applied to valves which open before the piston has passed tdc or bdc at the beginning of a stroke in the four stroke cycle. | |
Lead OxideMaterial used for the positive plate material in a battery. | |
Leading EdgeThe front edge of a brake shoe in relation to the direction of rotation of the brake drum. | |
Leading ShoeA brake shoe that has a leading edge making first contact when applied. Also primary shoe. | |
Leaf SpringMetal spring used on vehicle suspensions. Consists of one or more steel strips clamped together with a mounting eye at each end. The front eye is used for fixing to the chassis and the rear eye for fixing to a swinging shackle. Or it may have a mounting eye at the front and a flat end plate for a slipper shackle at the rear. | |
Lean Fuel/Air MixtureA fuel/air mixture with a ratio less than the stoichiometric ratio of 14.7:1. A mixture strength with an excess of air and therefore oxygen. | |
Learning styleThe way a person takes in, understands, expresses and remembers information; the way a person learns best. | |
LeatherA tough material produced from the skin of animals, by tanning or similar process. | |
LEDLight emitting diode. An electronic diode that emits light when an electrical current passes through it. | |
Legal RightsStatutory rights within law. | |
LegislationLaws. | |
Let-down PanelPanel made by a paint technician with different methods of application and amounts of material, resulting in different shades of the same colour. | |
LevellingThe flowing out of a paint film, occurring from the time the paint particles form a wet film on the surface to the time the film hardens and dries. | |
LeverA rigid rod or bar that moves about a fixed point. | |
LeverageThe use of levers to gain a mechanical advantage. | |
LHDLeft-Hand Drive | |
LibellousUntrue and harmful information. | |
LibraryCollection of materials i.e. books or cd's. | |
Lift PumpA low pressure pump used to supply a carburettor or diesel injector pump with fuel. Driven mechanically from a cam in the engine or electrically from the battery. | |
LiftingAttack by the solvent in a newly-applied paint on the substrate which results in distortion or wrinkling of the preceding dried or partially cured layers. | |
Light MeterA meter that measures light intensity. | |
LightnessThe brightness of a paint or object compared to a perfect white. Measured by the amount of light reflected by a surface. A perfect white is one which reflects 100% of the light in the visible spectrum. | |
Limit SwitchA switch that operates by a linkage at the limit of its movement. For example, a wiper motor has a switch that operates when the blades are in the park position. | |
Limited Slip DifferentialFinal drive differential with a clutch or other device to limit the differential action when one wheel loses traction. | |
Limp HomeElectronic control systems on later vehicles can substitute faulty sensor signals and therefore a vehicle can 'limp home' even when a fault occurs. | |
LINThe LIN-Bus (Local Interconnect Network) is a vehicle bus standard or computer networking bus-system used within current automotive network architectures. Local interconnect network (LIN) is a single-master, multiple-slave networking architecture originally developed for automotive sensor and actuator networking applications. | |
LinearFor an equal increase in one variable an equal increase occurs in another. | |
Linear ValveA valve where the movement is proportional to the change in opening size. | |
Liner (Cylinder)A steel sleeve used to form a running surface for pistons in an engine. Also known as a cylinder sleeve. | |
LiningThe friction material attached to brake pads, shoes and clutch friction plates. | |
LinkageGeneral term used to describe a collection of components that operate something. | |
Lip SealAn oil seal with a lip that is reinforced with a coil spring and is used to retain oil on a revolving or reciprocating shaft. | |
Liquid LeverHydraulic cylinders that increase the force applied. | |
Little EndEnd of the con rod that fits to the piston. | |
Live AxleAn axle that transmits a drive to the wheels. Also known as a drive axle. | |
Live FeedElectrical supply from (usually) the battery positive, possibly via the ignition switch and a fuse. | |
LoadDescription of how hard an engine is working. | |
Load Carrying MemberA component of a chassis which carries or supports the weight of the vehicle, the engine or other mechanical system. Any other component that carries a load. | |
Load Sensing ValveA valve in the rear brake circuit of a goods carrying vehicle that responds to the weight of load to vary the braking effort of the rear wheels. | |
Loading (Clogging)The build-up of flatting residue between the abrasive particles on flatting papers or discs during use. Loading reduces the cutting effectiveness of the abrasive. | |
LobeThe lever component of a cam set on an eccentric orbit from the centre axis of the shaft. | |
Lock (Steering)The amount that the front wheels are able to turn from the straight ahead position to fully turned. Measures either as an angle of turn or the diameter of the minimum turning circle. | |
Lock NutA nut that is used to lock another nut or threaded component in position on a threaded rod or stud. Also jam nut - US term. | |
Lock TabSpecial washer that can be bent over to lock a nut or similar. | |
Lock-up ClutchAutomatically operated clutch in a torque converter applied during constant speeds to lock the input and output components together. | |
Logic GateA simple electronic device, which has an output that is dependent on its input of combinations of inputs. Common types are described as AND, OR and NOT. | |
Logic ProbeHigh resistance tester (so it does not load the circuit), that is used to check the logic state (1/0 or high/low voltage) of a circuit. | |
LongevityLong life, long duration of service,durability
| |
LongitudinalAny axis running from the front to the rear of a vehicle or other object. | |
Longitudinal AxisAny axis running from the front to the rear of a vehicle and parallel with the ground and the sides of the vehicle. The main vehicle axis runs through the centre of gravity of the vehicle. | |
Longitudinal ForcesForces acting along the length of a vehicle. | |
LoomThe collection of vehicle cables wound together with an insulation tape. Also known as a 'wiring harness'. | |
LOSLimited Operation Strategy. Get home or limp home mode of ECM when system failures occur. | |
Low BoilersSolvents with low boiling points, usually less than 50 degrees Celsius. | |
Low Film BuildThe condition of a paint film when it is too thin to provide protection to the substrate or withstand environmental conditions. | |
Low Profile TyreTyre with an aspect ratio less than 80%. The depth of the tyre is less than the width by the percentage value. | |
Low TensionThe term used for the low voltage in the primary circuit of the ignition system. | |
Low Tension CircuitThe ignition coil primary or control circuit operating at battery voltage (low tension). | |
Lower Control ArmThe lower and longer wishbone in an independent suspension system. | |
Lower QuartileData is split into 4 equal quarters. The lowest quarter is referred to as the Lower Quartile. For example the Lower Quartile of 100 is the lowest 25 of the numbers. | |
LPGLiquid Petroleum Gas. | |
LTFTLong Term Fuel Trim | |
LubricantOil, for example, to prevent surface contact. | |
LubricationMinimise friction with oil, grease, etc. | |
LUSLock-up solenoid. Operates with PCM signal to apply the torque converter lock-up clutch. | |
LustreGloss or sheen of a finish. | |
LWBLong Wheel-Base | |
M |
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M.O.TMinistry of Transport. Colloquial for the annual inspection test for vehicles. | |
MAFMass Air Flow Meter. | |
MagnetAny material with the naturally occurring phenomenon that has the ability to attract iron. | |
Magnetic fieldMagnetic fields surround magnetic materials and electric currents and are detected by the force they exert on other magnetic materials and moving electric charges. The magnetic field at any given point is specified by both a direction and a magnitude (or strength). | |
Magnetic FluxThe force contained in a magnetic field. | |
Magnetic PoleThe ends of a magnet where the lines of force originate. The north and south poles. | |
Magnetic Pulse GeneratorA sensor that uses an iron core and electrical winding to induce an electrical current when passed by a toothed wheel or rotor. Also known as an inductive generator. | |
Magnetic StandA holding device for measuring equipment such as a dial test indicator. | |
MagnetismA natural force found in iron and some other materials. | |
MagnitudeThe height of a wave. The maximum voltage in an AC wave pattern. | |
Main BeamThe upper of the two headlamp beams. Also driving beam and upper beam. | |
Main BearingsCentral journals and bearings on a crankshaft axis mounted in the engine crankcase. The crankshaft rotates in these bearings. | |
Main GalleryA tube shaped section cast in to the engine block where other oil feeds are taken from. | |
Mainline PressureThe regulated hydraulic pressure in an automatic transmission. | |
Makeup AirA system that brings and heats air from the outside to a desired air flow and temperature. | |
MalleableDescribes a material that means it can be easily shaped. | |
MAMMaximum Authorised Mass – The maximum gross weight permissible in GB. | |
MandrelsBars used to locate a component. | |
ManifoldPipes or ducting to route air in or burnt gases out of an engine. Attached to the ports. | |
Manifold Absolute PressureThe mean gas absolute static pressure in an engine induction manifold. Absolute pressure is equal to gauge pressure plus atmospheric pressure. | |
Manifold VacuumThe depression or low pressure that occurs in the inlet manifold due to the increasing volume above the pistons when they are moving downwards in the cylinders. The airflow into a naturally aspirated engine cannot move quickly enough to fill the additional volume and therefore loses pressure and density. | |
Manual TransmissionTransmission system where the driver makes the gear shifts by means of a control (gear) lever and linkages to the gearbox. | |
Manual ValveThe gear selector valve in an automatic transmission operated by the driver. | |
MAPManifold Absolute Pressure Sensor. The mean gas absolute static pressure in an engine induction manifold. | |
Map LightSmall light used in a vehicle for illuminating a map! | |
MAP SensorA pressure sensor used to measure manifold absolute pressure in an engine induction system. | |
MappingUsed to identify opportunities for developing and assessing key skills within the curriculum. | |
Mapping (Contouring)Edge of a repaired area under a paint film that shows up after a surface has been repainted. | |
MaskingApplication of paper or other material and adhesive tape to cover an object that must be protected from overspray. | |
Masking PaperPaper designed to prevent paint from bleeding through. | |
MassThe total theoretical weight of matter based on its atomic structure. The weight of matter without gravitational pull. | |
Mass Air Flow MeterA sensing device in the air intake duct of a fuel injection engine that provides data for control of the quantity of fuel that is injected. | |
Master CylinderThe pump on a brake hydraulic system. | |
MATManifold Air Temperature | |
MatchingIn painting, to make refinishing colours look the same as the original finish. | |
MattA surface with minimal reflection. | |
MatterA term used to describe any substance as a 'quantity of atoms'. | |
Matting agentAn additive used to lower the gloss of topcoat, single-stage colours and clearcoats. | |
MbMegabyte. Used to measure computer memory. 1 Mb = 1,000,000 bytes or 1024 Kb (kilobytes). | |
MCMMotor control module | |
McPherson StrutTelescopic independently sprung suspension member incorporating a damper, and fixed at its upper end to the body. The lower end is located by linkages which counteract transverse and fore and aft movement. The original system used a track control arm for transverse forces and an anti-roll bar for longitudinal (fore and aft) location. Usually incorporated in a steered front suspension system. | |
MCSMixture Control Solenoid | |
MCTManifold Charge Temperature | |
MeanThe average value (the sum divided by the number of items). | |
Mechanical AdvantageThe effectiveness of a simple machine, such as a lever, inclined plane, wedge, pulley system or a screw at amplifying a force. | |
Mechanical EfficiencyThe ratio between the actual total output of a machine and the theoretical maximum output. | |
MechatronicsA combination of a mechanical and electronic control system | |
MedianThe middle number of a series when the data is arranged in ascending order. | |
MelamineUsed in 1K OEM finishes, a hard resin used to modify alkyd resins and other films formed used in baking finishes. | |
MemoryThe stored data in a microcomputer or electronic control module. | |
Memory ChipA chip that stores data. | |
Memory KeeperA battery or secondary power source used to preserve ECU memories when the main battery is disconnected. It can often be plugged in to the cigar lighter socket. | |
Memory SaverA battery or secondary power source used to preserve ECU memories when the main battery is disconnected. It can often be plugged in to the cigar lighter socket. | |
MeshCriss-cross fibres to produce a material with very small holes. Used to make filter elements. | |
Mesh (Gears)Gear teeth in contact. | |
Metal ConditionerAn acid-type cleaner which removes small amounts of rust and corrosion left from mechanical metal cleaning. Usually based on Phosphoric Acid solutions. | |
Metallic PaintTopcoat which contains metallic pigments, usually in the form of tiny flakes of aluminium. Custom finishes may use other non-ferrous metal flakes such as copper or bronze. | |
MetamerismA term used to describe colours that match under a specific light source, but do not match under all light sources. It is primarily caused by the use of pigments that are different to those used in the original formulation. | |
MeterMeasuring the flow rate of a gas or liquid. | |
MeteringWhen applied to fuel systems a control device for achieving the correct air/fuel mixture strength for specific engine running conditions. | |
Metering NeedleSee metering rod. | |
Metering PortsPorts designed to a set size to allow accurate flow of fuel or air. | |
Metering RodA tapered needle in a jet in a carburettor. The taper allows a varied or metered supply dependent on the position of the taper in the jet. | |
MethanolMethyl-alcohol used as a fuel or fuel additive. | |
MethodThe way in which a task is carried out. | |
Methyl Ethyl Ketone (MEK)A fast-evaporating solvent. | |
MetricEuropean standards of measurement based on the metre. | |
Metric MeasurementA system designed to regulate measurement. Each quantity has a single unit. These include; metre, kilogram, ampere. | |
MFIMultiport fuel injection. Usually known a port fuel injection or multipoint fuel injection (MPI). | |
MHMetal hydride | |
Micro ProcessorA processor on a single integrated circuit or chip. The calculator in a microcomputer or electronic control module. | |
Micro SwitchA small switch usually operated by a moving mechanism. | |
Micro-checkingA condition which appears as severe dulling of a paint film, but when viewed under magnification, is actually very fine cracking of the painted surface . | |
Micro-porousContaining lots of very small holes. | |
MicroelectronicsRefers to integrated circuit electronics usually involving some form of processor. | |
MicrometerMeasuring device based on an accurate screw thread. Measurements can be taken to 0.01mm/0.001''. | |
MicronA measure of paint film thickness, equal to one one-thousandth of a millimetre. | |
MicrophoneA device that converts sound waves to audio signals. | |
Microsoft OfficeA package of programs including Word Processor (Word), Spreadsheet (Excel), Presentation (PowerPoint), Email and Organisation (Outlook). | |
Microwave1. Essential equipment for use when a technician is hungry...2. High frequency radio waves. | |
Middle SolventA solvent that evaporates at a medium rate, leaving the paint primarily during flash-off. | |
MILMalfunction indicator lamp. Dashboard warning light from an electronic control module to signal a system or component failure. | |
MillingA machining process that uses a rotating blade to cut through the surface of materials. | |
MinibusA motor vehicle constructed or adapted to carry more than eight but no more than sixteen seated passengers (see also Bus). | |
Ministry PlateDisplays the maximum authorised weights at which a vehicle may be operated. This information supersedes the maximum weights displayed on the Manufacturer’s plate. | |
MiscibilityThe property of materials that mix easily. | |
MiscibleCapable of being mixed with or dissolved in other components of a paint, etc. | |
MisfireUneven running of an engine due to one or more cylinders not working properly. | |
MisrepresentationRepresent wrongly with false account (legal). | |
Mist CoatingA light sprayed coat of a paint material to assist in blending and/or gloss enhancement and metallic control in single-stage colours. | |
Mixing (Ratio) StickInstrument used to gauge the correct ratio of paint material being mixed for ready-to-spray configuration. | |
Mixing RatioThe proportion of ingredients to be mixed together to make a ready-to-spray paint. | |
mmMillimetres | |
ModeThe most common number in a series. | |
ModemModulator-demodulator. Used to convert computer signals so that they can be sent over telephone lines. | |
Modulating ValveA valve that can be switched on and off rapidly such as to control its partially open position. | |
Modulator AssemblyReleases and re-applies fluid pressure to brake units. (ABS). Adjusts and regulates. | |
Modulator ValveFlow control valve in power steering pump. In an automatic transmission a valve that responds to manifold vacuum to create hydraulic pressure feedback to the main control assembly. | |
ModuleAn electronic control unit for a vehicle system. | |
MolMethod of Inspection | |
MolecularRelating to atoms formed into molecules. | |
Molecular MassTerm used to describe the mass of molecules - usually relating to the mass of the protons and neutrons. | |
MoleculeThe smallest possible unit or amount of any substance which retains the characteristics of that substance. | |
MomentumForce that keeps a body moving. | |
MonitorThe screen that displays information produced on a computer. An output device. | |
MonolithThe honeycomb catalyst support element in a catalytic converter. | |
MonopointA petrol fuel injection system using a single point (or monopoint) injector in a throttle body in the inlet air supply and positioned on top of the inlet manifold. Also throttle body injection (TBI). | |
MoonroofSee also Sunroof... A sunroof that has a clear glass panel, rather than being opaque, so that light can enter the vehicle even when the roof is closed. Some vehicle have a sunroof at the front and a moonroof at the back. | |
MopedThree wheeled vehicle with max speed of 45km/h, not over 50cc for a petrol engine or 4KW for any other engine or electric motor, not more than 450kg ULW. | |
MOSTMedia Oriented Systems Transport. This protocol defines a multimedia fibre-optic point-to-point network implemented in a ring, star or daisy-chain topology over Plastic optical fibres. The MOST bus specifications define the Physical Layer as well as the Application Layer, Network Layer, and Medium Access Control. The MOST bus provides an optical solution for automotive media networks. | |
MOTMinistry of transport (UK) | |
Motor Reverse CircuitAn electrical circuit that reverses polarity supplied to a motor. | |
Motor tricycleThree wheeled vehicle with wheels symmetrically arranged, a max speed over 45km/h, or engine size over 50cc. | |
MottlingA film defect appearing as blotches or surface imperfections, normally due to metallic or pearlescent pigments not being properly orientated in the paint film. | |
Mould-Release AgentsChemical compounds applied to manufacturing moulds which must be removed by a pre-treatment prior to refinishing plastic parts to insure adhesion. | |
MountingGeneral term for the part of a component, or a separate component, which fits one thing to another. | |
Mounting StudsThreaded fixings for an exhaust flange or similar. | |
MountingsInsulated or solid attachments for components/units on the vehicle. Insulated versions absorb vibration and provide some protection from shock loads. | |
MouseAn input device that allows the user to move the pointer around the screen and click on different items to operate computer applications. | |
Moving ConductorThe armature in a motor or dynamo. | |
MPFIMulti Point Fuel Injection | |
MPGMiles Per Gallon | |
MPHMiles Per Hour | |
MPIMultipoint Fuel Injection. | |
MPVMulti-Purpose Vehicle | |
msMillisecond | |
MSDSMaterial Safety Data Sheets. | |
Muffler (Silencer)A component in the exhaust system to absorb the gas shock waves and noise in order to reduce the emitted noise from a vehicle engine. Also known as a silencer. | |
Multi-Plate BrakeA brake that uses several clutch-type plates. | |
Multi-plate ClutchA clutch mechanism having a series of friction and steel plates in a clutch drum assembly. One set of plates is splined to the drum and the other to a centre shaft so that drive through the clutch is via the drum, friction faces and the centre shaft. | |
Multi-vee BeltA flat drive belt with several ridges or vee shapes running circumferentially (the long way round). | |
Multigrade OilClassification for lubricating oils that change viscosity grades during temperature change. The lower number is the cold temperature grade and the higher number the hot temperature grade. These oils do not thin at the same rate as single grade viscosity oils as the temperature rises. Also known as multiviscosity oils. | |
MultimeterAn electrical measuring tool with functions for volts, amps and ohms. | |
MultiplateA clutch mechanism having a series of friction and steel plates in a clutch drum assembly. One set of plates is splined to the drum and the other to a centre shaft so that drive through the clutch is via the drum, friction faces and the centre shaft. | |
MultiplexedIn signal transmission where each set of signal pulses is given a certain time or frequency slot. This allows a great number of individual signals to be carried by a common conductor. | |
MultiplexerA unit used for signal transmission where each set of signal pulses is given a certain time or frequency slot. This allows a great number of individual signals to be carried by a common conductor. | |
MultiplexingA common conductor system for digital signal transmission where each set of signal pulses carries its own unique identity. This allows a great number of individual signals to be carried by the common conductor. | |
MultiplugA connector with more than one electrical terminal inside. | |
Multipoint Fuel InjectionGasoline electronic fuel injection system with injectors in each inlet manifold spraying fuel in towards the inlet valves in the ports of each cylinder. Also known as port injection. | |
MultisocketsSockets with many positions for fitting over a bolt or nut head. Sometimes described as multihex. | |
Mutual InductionThe electrical current induced in one conductor because of the electrical current flow and magnetic field produced around another conductor nearby. Used in transformers to induce a current in one winding from the electrical flow of another when both are wound around an iron core to create a magnet field. | |
mVMillivolts | |
N |
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NavePart of a wheel: connects the rim to wheel hub. | |
NavigationThe way in which you get around a program or website. | |
NDSNeutral Drive Switch. | |
Needle BearingA bearing made from small diameter rollers in between inner and outer bearing tracks. | |
Needle Valve(1) Valve by which fluid flow rate is controlled by the degree of insertion of a tapered needle into a fixed diameter orifice. This type of valve can provide a fine gradation of flow. (2) Valve in which a blunt, conically ended needle seats on a fixed diameter orifice. With this type of valve there is little or no gradation of flow, control being limited to full, with needle lifted, or none, with needle seated. | |
Negative CamberSteering geometry where the road wheel leans inward at the top. | |
Negative CastorAngle in side elevation between the steering and vertical axis. Steering axis hits the ground behind the vertical axis. | |
Negative CommunicationA comment or statement expressing lack of approval. | |
Negative Offset (Wheel)The position of the wheel nave or disc when inside the centre line of the wheel. | |
Negative ScrubNegative scrub radius steering geometry where a line through the steering swivel axis meets the road surface outside of the tyre centre line. | |
Negative Temperature CoeffcientSee Negative Temperature Coefficient. | |
Negative Temperature CoefficientType of resistor that has resistance reducing with increases in temperature. These resistors are used in electrical circuits to give temperature sensing and control. Thermistor. | |
Negative Temperature CoeficientSee Negative Temperature Coefficient. | |
NetworkInterlinked group of computers so that resources can be shared. | |
Network CardA piece of hardware that allows computers to be connected to a network. | |
NeutralGearbox position when no gear is selected and no drive transmitted. | |
Neutral Drive SwitchOn a transmission system, a switch that makes when neutral is selected. | |
Neutral SteerSteering condition when the vehicle follows a true line in relation to the steered wheels. | |
NeutronOne of a number of particles in the nucleus of an atom. The neutron has no polarity and is electrically neutral. | |
New and like-new finishesFinishes that have maintained a brilliant, high-gloss performance. | |
Newton (N)A standard unit of force. | |
Ni(OH)2Nickel di-hydroxide | |
NiMHNickel metal hydride – used in alkaline batteries. | |
NiOOHNickel hydroxide | |
Nip (Bearing)The amount by which shell bearing halves are clamped in order to secure them in their housing. | |
NmNewton Metres | |
Non IndependentDescribes suspension systems using a solid beam axle where the movement of one wheel affects the other wheel on the same axle. | |
Non-ferrousDescribes metals which contain no iron. | |
Non-metallicUsed to describe paint finishes that do not contain metallic pigments, i.e. Solid colours | |
Non-porousPrevents flow or holds back a liquid. | |
Non-Return ValveA valve that will allow fluid or gas to pass in one direction only. | |
Non-VerbalAny form of communication that does not use words, i.e. traffic lights, shaking somebody's hand and smiling. | |
Normally AspiratedNon pressure-charged engine using atmospheric pressure and cylinder vacuum to charge the cylinders. | |
North PoleThe term used to describe one of the poles of a magnet where the magnetic field lines of force start. | |
NOxOxides of nitrogen. An exhaust emission pollutant. | |
NozzleThe tip of an injector from where the fuel is sprayed. | |
NTNominated Tester – a person nominated by an AE to carry out tests, Inspectors appointed by Designated Councils to carry out tests, all of which are approved by VOSA. Also VOSA staff appointed under section 66A of the Road Traffic Act 1988. | |
NTC ResistorType of resistor that has resistance reducing with increases in temperature. Used for temperature sensors. | |
NucleusThe mass of neutrons and protons at the centre of an atom. | |
NVRAMNon-volatile Random Access Memory | |
O |
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O RingsCircular rubber rings used to seal pipe and other connections. | |
O2Oxygen | |
O2 SensorOxygen sensor, lambda EGO or HEGO sensor to provide exhaust oxygen content signal to the ECM. | |
O2SOxygen Sensor | |
OBDOn board diagnostic. A connector for diagnostic analysis of a vehicle's electronic systems. | |
OBD IOnboard Diagnostics One | |
OBD IIOnboard Diagnostics Two | |
ObjectiveThe goal intended to be attained and which is believed to be attainable. | |
Objective InformationInformation that is unbiased and open minded. | |
ObligatoryCompulsory. | |
ObsceneOffensive, foul, disgusting. | |
OCOxidation Catalyst. | |
OccupationThe job that you do. For example, training to be a motor mechanic is training for an occupation. | |
Octane RatingThe anti-knock property of petrol fuel. The octane rating or number is a comparison against two standard fuels, heptane and iso-octane having values of zero and 100 respectively. Most road vehicles use petrol with octane ratings between 93 and 98. | |
ODOutside Diameter | |
OdometerInstrument that displays distance travelled by vehicle. | |
OEOriginal Equipment | |
OEMOriginal Equipment Manufacturer. | |
OffensiveTo attack somebody/something. | |
Office ApplicationsA package of programs including Word Processor (Word), Spreadsheet (Excel), Presentation (PowerPoint), Email and Organisation (Outlook). | |
OffsetAny point that is not on the axis of shaft or component. | |
OHCOverhead cam - type of valve operating gear. Camshaft in cylinder head above the valves. | |
OhmElectrical unit of resistance. | |
Ohm's LawThe electrical law, named after its originator, that shows the relationship between electrical pressure in volts, electrical current in amps and the electrical resistance in Ohms is proportional. Volts is equal to amps multiplied by Ohms. | |
OhmmeterA meter for measuring Ohms, the standard unit for electrical resistance. | |
OHVOverhead valve - type of valve operating gear. Camshaft in cylinder block connected to valves by push rods and rockers. | |
Oil CoolerA small heat exchanged (radiator), which has oil pumped through so that a flow of air will cool it. | |
Oil DilutionThe thinning of engine oil by fuel flowing down the cylinder walls into the oil pan. | |
Oil DrillingsHoles through various engine components, such as the crank, to allow oil to flow. | |
Oil PanSump that holds oil for lubricating the engine. | |
Oil PumpAn mechanically driven pump used to supply oil pressure. | |
Oil SealA seal that prevents oil loss. Usually described as a radial lip seal but other types are used. | |
Oil SeparatorPlates or baffles used to prevent oil being mixed with air or drawn through air pipes. | |
Oil StrainerThe mesh filter on the end of an oil pick up pipe. | |
Oil-Based PaintsPaints which dry by absorbing oxygen from the atmosphere. This 'uptake of oxygen' promotes a chemical reaction which is irreversible. | |
On Board Diagnostics (OBD)See OBD | |
One-way ClutchAn automatic mechanical clutch that permits drive from one shaft to another in one direction only. A drive transmitted to the outer hub of the clutch bypasses the inner hub and the clutch free wheels. This type of clutch allows drive to be transmitted by two alternative routes and at different rotational speeds. | |
OpacimeterSmoke meter used to measure the amount of smoke in diesel engine exhaust gases. | |
OpacityThe ability of a paint film to obliterate the colour or pattern of a surface. Opacity is measured by determining the minimum thickness at which a paint film will completely obscure a black and white pattern. | |
OpaqueImpervious to light transmission -non-transparent. | |
Open CircuitApplied to an electrical circuit when the switch is 'off' or the circuit is not continuous. | |
Open CoatA type of abrasive paper coating in which the abrasive particles are scattered in a low density to prevent it from clogging up. Typically found in Production Papers | |
Open Period(1) The number of degrees of distributor rotation during which the primary circuit remains open. (2) The number of degrees of crankshaft rotation during which an inlet or exhaust valve remains open. | |
Open-loopAn electronic control system using a comparison of sensor signals and a pre-programmed map. | |
Operational SafetySafety aspects that are operational during use of a vehicle. | |
Optical GaugeA measuring instrument that uses light/reflection to align steering (for example). | |
OPTLOne Person Test Lane. These are lanes authorised by VOSA to conduct testing where the tester has the option of not using an assistant if so desired. | |
Orange cablesThese indicate high voltages – take care. | |
Orange PeelAn irregularity in the surface of a paint film resulting from the inability of the wet film to "level out" after being applied, caused by a lack of flow. Orange peel appears as a characteristically uneven or dimpled surface to the eye, but usually feels smooth to the touch. | |
Orbital SanderType of sander that uses a circular motion to accomplish the sanding of different materials. | |
Organic MaterialsCompounds composed of carbon, hydrogen, and other elements with chain or ring structures. | |
OrificeA hole, usually with a precise drilling diameter to control a fluid flow or spray. | |
OSOxygen Sensor | |
OscillateTo move or swing from one place to another (e.g. side to side). | |
OscillatorAn electronic circuit that produces as signal of a set frequency. | |
OscilloscopeAlso shortened to ‘scope'. An instrument that draws an image to represent changes in voltage over a set time period. | |
Otto CycleAn alternative term for the four stroke engine cycle using the name of its inventor. | |
Out-of-roundA term used to describe a component that should be perfectly round or cylindrical but is not. Usually caused by wear but can be from faulty machining. | |
Outdoor ExposureThe most realistic way to measure the behaviour of a paint film. Manufacturers paint sample panels and leave them exposed to the elements for long periods of time, and inspect them at intervals to measure the effects of the exposure. | |
Outer RacesThe outside rings of ball or roller bearings. | |
Outgoing Telephone CallTo make a telephone call to somebody. | |
Outlet PortsUsed to describe any port that allows a gas or liquid to leave. Exhaust ports are a good example. | |
OutputPower or data that comes out from a mechanical unit or electronic control module. Usually adapted or modified by the unit or module to suit a particular purpose. | |
Output CircuitThe battery charging circuit for the electrical current from a generator. | |
Output DeviceA device that allows information from the computer to be displayed. Egg, monitor, printer. | |
Output ShaftShaft that outputs drive from a gearbox to a propshaft or final drive. | |
OvenEquipment used to bake paint finishes. Originally developed by vehicle manufacturers, whose applied finishes may require temperatures as high as 180°C to cure. In the refinishing industry, ovens are used to bake sprayed coatings at varying temperatures up to 80°C, producing fully-cured finishes in as little as 20 minutes. | |
Over-thinTo add more thinner or reducer to a paint than is normally necessary for application. This is sometimes done in order to lower the paint viscosity, to aid in blending, or to achieve a special colour effect with metallics or pearlescents | |
Overall PaintingA type of refinish task in which the entire car is completely repainted. | |
Overall RatioThe term used to describe the output ratio of a series of mechanical components such as gears or levers. | |
OverbakeThe result of curing a paint film at too high temperature, or for longer than the specified time. The film often becomes too hard and brittle. | |
Overdrive GearA gear drive that increases the rotational speed of the output shaft above that of the input shaft. | |
Overdrive UnitA separate unit that at one time was fitted on the output shaft of a gearbox. It produces a higher gear ratio. | |
OverlapThe area of coverage in which one spray pass is extended over and partly covered by the next pass. | |
Overlap (Valve)The term used to describe the angle of crankshaft rotation when the inlet and exhaust valves are both open. | |
OverrunMovement of vehicle when engine is not under power. Engine braking. | |
Overrun Clutch(1) A clutch on a starter drive pinion that prevents the engine from driving the starter motor after the engine has started. (2) A one-way clutch in an automatic transmission. | |
OversprayAn overlap of dry spray particles landing on areas that were not meant to be painted, or on previously painted areas where they do not blend in. | |
OversteerSteering condition of a turning vehicle when the vehicle attempts to turn by a greater degree than the steered position taken by the driver. A difficult driving condition requiring opposite lock to control. | |
OxidationThe chemical combination of oxygen and the binder of synthetic-enamel type paints which leads to drying. Also refers to the destructive combination of oxygen with a dry paint film leading to age degradation, or the destructive combination of oxygen and metal commonly known as Corrosion. | |
Oxygenated SolventAn organic solvent containing oxygen as part of the molecular structure. Alcohols and ketones are oxygenated compounds often used as paint solvents. | |
OzoneA colourless gas (O3) soluble in alkalis and cold water; a strong oxidizing agent; can be produced by electric discharge in oxygen or by the action of ultraviolet radiation on oxygen in the stratosphere (where it acts as a screen for ultraviolet radiation). | |
P |
---|
P/BPower Bakes | |
P/NPark and neutral position switch for sending signals to the PCM. | |
P/SPower Steering Pressure Switch. Also PSP switch. | |
PAPressure Air | |
PaceThe relative speed of progress or change. | |
PaintA material which, when applied as a liquid to a surface, forms a solid film for the purpose of decoration and/or protection. Generally, any paint contains a binder, solvent, and pigment plus other chemicals or additives giving the paint its special characteristics or properties. | |
Paint RemoverA chemical, usually a mixture of acid and solvents that breaks down an old paint finish by liquefying it, thus allowing it to be completely removed from the substrate. | |
Paint StrainerA disposable fine mesh filter used to clean paint as it is poured into the gun cup. | |
Paint thickness gaugePrecision instruments to accurately measure the dried film thickness of painted objects by non-destructive testing. On ferrous substrates, they operate by measuring the resistance to the flow of magnetism between two probes, and on non-ferrous surfaces special gauges use the 'Eddy Current' principle | |
PAIRPulsed Secondary Air Injection | |
PanAlternative name for a sump. | |
Panel LightsIllumination for instruments and other displays. | |
Panhard RodRear axle transverse link between the chassis and axle beam. It is used to hold the axle in relation to the body during cornering or for sideways forces. | |
ParaffinA petroleum based thin and colourless fuel oil, (kerosene in US English). | |
ParallelThe condition that exists when the centre lines of two or more items or components or lines do not converge. The extended lines in both directions will always remain at an equal distance apart. | |
Parallel circuitA circuit that splits into two or more branches. A break in one will not stop current flowing in the other(s). | |
Parallel hybridThe engine and motor can both be used to drive the vehicle (most hybrid vehicles use this system). | |
Parasitic drawAn unwanted, usually small, current flow from a battery. | |
Parking BrakeMechanical system of braking to hold vehicle stationary. | |
Parking GearThe component(s) in an automatic box that lock the drive when 'Park' is selected. | |
Particle SizeThe size of the pigment particles in a dispersion (e.g. paint). | |
ParticulatesExhaust pollution consisting of very small particles of matter (soot) that are produced as a by-product of combustion. Seen as smoke in a vehicle exhaust, particularly from diesel engines. | |
PASPower Assisted Steering. | |
Pascal (Pa)Standard unit of pressure (N/m2) named after a scientist who studied pressure in liquids. Pascal's principle of the transmission of pressure in fluids established that the pressure in a completely filled container is equally applied throughout and any change in pressure is transferred to all parts of the fluid and walls of the container. | |
PassivationThe conversion of a metal surface to a less reactive state. A process used by vehicle body manufacturers to reduce the corrosion rate of a metal surface, particularly low-carbon steel. | |
Passive RestraintSafety features of a vehicle that act only in an accident. Seat belts, head restraints, air bags and pre-tensioners are examples. | |
PasswordPersonal Identification, used in conjunction with a Smart Card to access the MOT database via the VTS device. Can be numbers or letters, or a combination of both. | |
PawlPart of the ratchet mechanism that holds the ratchet. A pivoted tooth that engages in the teeth of the ratchet wheel to either prevent the pawl lever or the wheel from rotating in one direction only or in some mechanisms to drive the wheel forward. | |
PCMPowertrain Control Module. | |
PCVPositive Crankcase Ventilation. A series of pipes and valves connecting the engine crankcase to the inlet manifold or air cleaner in order to reduce oil vapour emission to atmosphere. | |
PDUPower drive unit | |
Pearls (Pearlescents)Finishes which include mica flakes in addition to the pigment and binder. These finishes are highly decorative and often give the impression that the colour alters as the viewing angle is changed. | |
PECVPower Enrichment Control Valve | |
PeelingThe failure of a paint film to adhere to its substrate. Peeling results when contaminated surfaces are painted, when there is an excessive difference between paint and surface polarity or thermal expansion, or when there is solvent incompatibility. | |
PentagonThe Pentagon, is a government building with five sides that serves as the headquarters of the United States Department of Defence. A pentagon, is a five sided shape. | |
PercentThe proportion of one part of something to the whole. Usually out of 100 (‘per' means ‘out of' and ‘cent' means ‘hundred'). | |
Percentage ChangeChanged amounts divided by the original value, then multiplied by 100. | |
Perceptual SafetyA reference to how safe the driver and passengers feel. | |
PerimeterThe sum of all the outside edges of a shape. | |
PerishingDescription of how some components, particularly if rubber-based, can decay. | |
PerpendicularAt ninety degrees to another plane or line. | |
PetrolVolatile hydrocarbon fuel for spark ignition engines. Also gasoline. | |
Petroleum JellyA type of grease used for battery terminals. Vaseline is a refined version. | |
PferdestärkeThe German word for horsepower. Pferdestärke. 1PS equals 0.986bhp. | |
PFIPort Fuel Injection. | |
PGPulse Generator. | |
PH valueA measure of the acidity of a substance in an aqueous solution. Pure water has a pH value of 7 and is classified as neutral. Below 7 is acid and above 7 is known as basic. The scale is from 0 (strong acid) to 14 (strong base). | |
PhaseThe time span between the start and end of a single wave moving from zero to positive and negative positions and returning to zero. | |
Phase SensorSensor that indicates camshaft position and hence where the engine is in its cycle. | |
Phasing (diesel injection)There are a number of phases of injection: fill phase, spill phase, injection phase and the pressure reduction phase. | |
Phosfor BronzeSee Phosphor Bronze. | |
PhosphatingA process used by vehicle body manufacturers which results in the formation of a layer of zinc, iron, or manganese phosphate crystals on the surface of the part to be painted. In modern vehicle construction plants, phosphating is achieved by complete body immersion. | |
Phosphor bronzeA material that can absorb oil making it ideal for making bushes/bearings. | |
Phosphoric AcidAn acid commonly used as a catalyst to speed up the cure of Etch primers and some baking finishes, usually alkyd/nitrogen resin combinations. Also a cleaner used for removing surface corrosion from ferrous metals. | |
PhotoelectricThe generation of an electrical current by light shining on certain materials such as some semiconductor devices. Photoelectric cell, photodiode or phototransistor. | |
PhototransistorA transistor that is operated by light. | |
PhraseA group of words in sequence. | |
Physical layerHardware, actual components and wires as opposed to software. | |
Pi3.141592 (3.142). | |
Pick Up PipeOil pipe that picks up oil from the oil pan. | |
PicklingThe use of a chemical solution (usually acidic) to prepare a surface for painting or bonding by dissolving away surface oxides and other impurities. | |
PIDParameter ID | |
Piezo-resistiveA special crystal that changes resistance as pressure is applied. | |
PiezoelectricVoltage produced by shock waves on a piezo crystal. Used in engine knock sensors. | |
PigmentSmall particles added to paint to influence properties such as colour, corrosion resistance, mechanical strength, etc. Pigments may be coloured, semi-transparent, black, white, or colourless. They must be incorporated into a paint system by very efficient dispersion processes. | |
Pilot BearingSmall bearing usually where two shafts meet. See also Spigot. | |
PingingNoise heard from an engine when the ignition of fuel occurs too early (advanced) in the cycle. Also 'ping'. | |
PinholingA defect consisting of tiny holes in the dried paint surface. Defects such as pin holing, popping, bubbling, and cratering are usually caused by solvent vapours forming from the substrate or the paint and rising to the surface. | |
PinionA small gear wheel or the driver of a meshing pair of gear wheels. | |
Pinion GearA small gear wheel or the driver of a meshing pair of gear wheels. | |
Pinion ShaftA shaft on which a small gear runs. | |
PinkingNoise heard from an engine when the ignition of fuel occurs too early (advanced) in the cycle. Also 'ping'. | |
PintauxType of injector for an indirect injection engine. Similar to pintle but with additional small injection orifice for low engine speeds. | |
PintleType of injector for an indirect injection engine. Uses a spring-loaded needle that is raised by fuel pressure to allow a spray of fuel to enter the pre-combustion chamber. | |
PIPProfile Ignition Pick Up Signal. | |
Pipe UnionA joint in a pipe. | |
PistonReciprocating component, usually in the form of a cylinder closed at one end, that operates under fluid pressure within a smooth walled cylinder. In a reciprocating engine, gas pressure on the piston crown provides the prime force that is converted into rotating mechanical power by the crankshaft. | |
Piston BlowTerm used to describe gases blowing past the piston rings. | |
Piston CrownThe top of the piston. | |
Piston RingSealing rings usually made of cast iron. Fitted on to a piston to make a gas tight seal. | |
Pitch(1) Distance that two points are apart. Examples are thread dimensions and pitch circle diameters of concentric drillings. (2) Vehicle body movement from back to front or from front to back. | |
Pitman ArmThe output arm on a steering gearbox. Also known as a drop arm. | |
PittingThe appearance of holes or pits in a paint film while it is wet. May also refer to the damage caused by more serious rusting on steel panelwork | |
Pivot BoltA simple bolt on which something pivots (turns). | |
Pivot PointThe point about which something pivots! | |
Planet CarrierFrame with spindles that the planet gears rotate on as part of an epicyclic gear set. | |
Planetary GearsGears that rotate around sun gears (differential, epicyclic gearing, etc.) | |
PlanningThe act of forming and following a program to achieve a specific goal. | |
PlanometerA flat metal plate for gauging the accuracy of a plane surface in precision metalworking, which is also known as a surface plate | |
Plastic FillerA compound of resin and heavy pigments used to fill dents on car bodies. | |
PlasticizerA low molecular weight substance added to polymeric materials such as paints to improve their flexibility. | |
PlastigaugeBrand name of a product that is used to determine bearing clearance. | |
Plate GridsBasket like holders to contain the active material in a battery. | |
Plate LugA connection point on the battery plate. | |
PlenumA chamber in the air inlet system to provide even air supply to all cylinders. | |
PliesRayon cords used in tyre construction. | |
Plug ThreadScrewed thread that is designed for a spark plug. | |
Plunge JointA shaft joint or coupling with provision for axial or plunging movement. | |
PlungerAlternative term for a piston or needle in a pump, slave cylinder or injector. | |
Ply (Tire)Fabric layer used in the construction of a tire. | |
Ply (Tyre)Fabric layer used in the construction of a tyre. | |
Ply RatingLoad rating of a tyre. | |
PneumaticTransfer of force by air or gas. | |
Pneumatic SuspensionSuspension system using air or gas springs. | |
PNPPark/Neutral Switch | |
PodgerA tool in the form of a short bar, usually tapered and often incorporating a spanner/wrench at one end. | |
PointsThe switching contacts of an ignition contact breaker. | |
Polarised LightLight that has been filtered so that its rays oscillate only in one direction. | |
PolarityA description of a component that must have positive and negative connections connected correctly. | |
Polarity (Electrical)Electrical positive and negative charges. | |
Polarity (Magnetic)Magnetic north and south poles. | |
Polarized LightLight that has been filtered so that its rays oscillate only in one direction. | |
PoleThe ends of a magnet where the field lines are emitted. | |
PolishA specially formulated blend of components designed to remove minor paint surface imperfections, such as fine scratches, light oxidation, water spots, and swirl marks left by the use of rubbing compounds. | |
PolishingThe use of polishes, either by hand or machine, to level and provide more gloss to a finish. | |
Polishing CompoundA mild abrasive material applied to a vehicle's painted surface which removes minor imperfections with minimal cutting action. Buffing restores film to a high gloss appearance. | |
Polishing WaxA combination of wax and polish that contains mild abrasives. The abrasives remove minor paint imperfections. The wax and other ingredients produce a durable, high-gloss finish. | |
PollutionProducts or by-products that destroy purity or make environments foul or filthy. | |
PolyesterA 2K resin used as the binder for plastic fillers, fibre glass laminations and high-build primers | |
Polyester StopperA finer grade 2K plastic filler material used to fill minor imperfections such as pinholes in filler prior to priming. | |
PolymersA naturally occurring or synthetic compound consisting of large molecules. Used for many purposes, one of which is as a polish. | |
PolypropyleneManmade plastic material used for electrical insulation, bumpers and other trim components. | |
PolyurethaneA 1K or 2K plastic-based paint finish that is characterised by durability and high gloss. Also, used for manufacturing some plastic and flexible parts. | |
Poppet ValveConventional inlet and exhaust valves having a circular plate at right angles to a central stem that runs through a guide tube. | |
PoppingA paint defect characterized by raised domes in the surface caused by solvent vapour forming within the paint after it has begun to "skin over." Often caused by baking at too high a temperature or before adequate flash-off time has been allowed. | |
Population of UKNumber of people that live in the UK. | |
PorosityProperty of a material that allows fluid to soak into or through it. | |
PortHole or aperture shaped to facilitate the flow of gas or liquid into or from a chamber. Usually denoted by its function, as inlet port or exhaust port. | |
Port Fuel InjectionPetrol electronic fuel injection system with injectors in each inlet manifold spraying fuel in towards the inlet valves in the ports of each cylinder. Also known as multipoint injection. | |
PortfolioThis is usually a folder that contains the evidence chosen to illustrate competence to satisfy individual key skills requirements. | |
Position SwitchA switch used to feedback position of a moving component. | |
Positive CamberSteering geometry where the road wheel leans outward at the top. | |
Positive CastorAngle in side elevation between the steering and vertical axis. Steering axis hits the ground in front of the vertical axis. | |
Positive CommunicationA comment or statement expressing approval. | |
Positive Crankcase VentilationA series of pipes and valves connecting the engine crankcase to the inlet manifold or air cleaner in order to reduce oil vapour emission to atmosphere. | |
Positive DisplacementA term applied to pumps which transfer liquid in the same quantity as the volume in the pumping chamber for each action of the pump. | |
Positive Offset (Wheel)The position of the wheel nave or disc when outside the centre line of the wheel. | |
Positive ScrubPositive scrub radius steering geometry where a line through the steering swivel axis meets the road surface inside of the tyre centre line. | |
Positive Temperature CoefficientType of resistor that has resistance increasing with increases in temperature. The normal response for metal conductors. These resistors are used in electrical circuits to give temperature sensing and control. | |
PotentialEnergy stored in a stationary object or chemical combination that has the capacity to do work. | |
Potential DifferenceDifference of electric potential between points (pd) volts. | |
PotentiometerA variable resistor with manual operation that provides an output voltage from a sliding terminal on a resistor block. | |
Pounds FeetOld unit of torque. Also foot pounds. Torque is now given in the SI units of Newton metres Nm. | |
Pour PointApplied to fuel oils (diesel) to indicate the temperature where it will still flow under its own weight. The pour point specified value is 3 degrees above the point where it will only just flow. | |
Powder CoatingsAny protective coating which is applied to the surface as a dry, finely ground powder and then carefully heated above its melting point so that the powder particles flow together to form a continuous film. | |
PowerThe rate of doing work. It is measured by the standard unit called the watt (W) and is equal to one joule per second. This is a very small unit and kilowatt (kW) or megawatt (MW) is more often used. Also, Horsepower which is the old term for power. | |
Power Assisted SteeringThe use of a hydraulic or electrical system to increase the driver's effort on the steering wheel thus reducing the effort that the driver has to apply. | |
Power BoosterHydraulic or pneumatic brake pedal or hydraulic pressure booster. | |
Power DistributionA central point from which various components are supplied. | |
Power OutputPower developed by an engine. | |
Power split hybridA combination of a series and parallel hybrid that uses a mechanical splitting device. | |
Power StrokePart of the four-stroke cycle following combustion. | |
PowertrainTerm used to describe the engine, transmission and driveline components as a unit. | |
PPEPersonal protective equipment | |
PPMParts Per Million | |
Pre-ignitionSpontaneous ignition in a petrol engine that occurs before the controlled ignition point. Can be caused by an overheated engine, incandescent particles in the combustion chamber or incorrect fuel. | |
PreignitionSpontaneous ignition in a petrol engine that occurs before the controlled ignition point. Can be caused by an overheated engine, incandescent particles in the combustion chamber or incorrect fuel. | |
PreloadAdditional tightening of a bearing or component after the backlash or free play has been eliminated. Used to eliminate backlash after the bearings have bedded in. Usually set by a Nm or angular torque. | |
PresentationThe way in which something is displayed. | |
PressurePressure is the product of a force multiplied by the area on which the force is applied. The standard unit of pressure is the Pascal which is equivalent to one N/m2. | |
Pressure BleederA brake/clutch bleeder that forces fluid through the system. | |
Pressure CapCap used to pressurise cooling system. | |
Pressure ChamberAn area used to hold a pressure as something expands of to supply pressure. | |
Pressure ChargedAn engine using a pressure-charger to boost the air charging pressure above atmospheric pressure, to increase the air mass entering the cylinders of the engine. | |
Pressure ConsciousVariable opening valve used for sensing and adjusting the pressure in brake circuits to restrict force to the rear brakes. | |
Pressure DifferentialThe difference in pressures between two sides of a component or areas in a system that are used to operate the component or system. Atmospheric pressure is often used in conjunction with a vacuum to provide a force. | |
Pressure GaugeAn instrument for measuring pressure of a fluid or a gas. | |
Pressure ModulatorA device for controlling pressure in a system. | |
Pressure PlateComponent of the clutch. | |
Pressure RegulatorA valve in a hydraulic system that controls line pressure. | |
Pressure Relief ValveThe valve in an oil or hydraulic circuit that opens to release excess fluid pressure and return fluid to the feed side of the pump. | |
Pressure SwitchA pressure sensitive switch used to provide a signal voltage to an instrument, lamp or electronic control module. | |
Pressure Wave SuperchargerA supercharger using the exhaust pressure waves to boost the inlet air pressure. This supercharger uses a drum with longitudinal drillings that is rotated in time with the engine and ported to match inlet and exhaust pressure waves together. | |
Pressure-feed GunA spray gun equipped with a separate paint container that is pressurized and connected to the spray gun by means of a solvent-resistant fluid hose, in addition to the normal air hose. | |
Primary ShoeA brake shoe that has a leading edge making first contact when applied. Also leading shoe. | |
Primary WindingThe low tension (primary circuit) coil of wire in an ignition coil. | |
PrimerThe first coat of paint applied to a substrate. Depending on the formulation of a particular primer, its function can be to provide any combination of">adhesion, build, scratch-filling, ground coating and corrosion resistance. | |
Primer-sealerAn undercoat which improves adhesion of the topcoat, by sealing off old painted surfaces that have been sanded; usually does not require sanding when dry. | |
PrimingLifting fuel into the system components to remove air. | |
Priming PumpA manually operated pump that lifts fuel into the system. | |
PrinterAn output device that allows data from the computer to be displayed on paper. | |
ProcessorThe central processing unit oversees all of the other components of the system. Can be thought of as the brain of the computer. | |
ProgressionInitial acceleration of the throttle after the idle position. Going onward/upward. | |
Progressive CarburettorUsually a carburettor with two chokes, the second of which only opens as the throttle is pushed further down. | |
PROMProgrammable Read Only Memory. | |
Propeller ShaftConnects gearbox to final drive and transmits torque on rear wheel and four wheel drive vehicles. | |
Propellor ShaftSee Propeller Shaft. | |
ProportionThe relation of one thing to another. | |
Proportioner ValveA valve used in hydraulic brake circuits to split the force between the front and rear brake circuits. | |
PropshaftConnects gearbox to final drive and transmits torque on rear wheel and four wheel drive vehicles. | |
Propshaft JointsUniversal joints used to allow a propshaft to work through an angle. | |
PropulsionApplication of a driving force. | |
ProtonOne of a number of particles in the nucleus of an atom. The proton has a positive polarity and is electrically positive in opposition to the negative charge of the electrons. | |
PrototypeA working version of a new design. | |
ProvenanceThe origins of information. | |
PSThe German word for horsepower. Pferdestärke. 1PS equals 0.986bhp. | |
PsiPound per square inch. A measure of pressure in old units. The SI unit of pressure is the Pascal (Pa). | |
PSPPower Steering Pressure | |
PSPSPower Steering Pressure Switch. | |
PTPart Throttle. | |
PTCPending Trouble Code | |
PTO - Power Take OffA supplementary drive from a vehicle transmission that is used to drive to auxiliary units. | |
Pull-in WindingA winding in a starter motor solenoid that actuates the solenoid to pull the switch contacts together. It is often earthed through the armature so that the drive pinion rotates as it moves into mesh with starter ring gear. | |
Pull-off SpringA simple return spring to open or close something after it is switched off. | |
PullerA tool for applying a pulling force. For example, to remove a gear from a shaft. | |
PulleysUsed to transmit or receive drive from a belt. The alternator pulley is a good example. | |
PulsationOn/off or increase/decrease in pressure or position. | |
Pulsation DamperAny device, such as a hydraulic accumulator, for damping pulsations in a fluid system, as for example the pressure pulses from a fuel pump. | |
PulseA change in electrical or mechanical signal. | |
Pulse Air InjectionAn emission control system that uses exhaust pressure pulsations to draw air into the exhaust gas flow to increase the available oxygen in the catalytic converter. | |
Pulse GeneratorInductive electronic device that provides information to the ignition amplifier or ECU on engine position. | |
Pulse ShapingThe action carried out in an ECU to a signal from a sensor. For example, a sine wave may be changed to a square wave. | |
Pulse WheelToothed sensor wheel used to induce or affect electrical currents in magnetic inductive pulse generators, such as engine speed and position sensors. | |
Pulse WidthThe operating phase of an actuator when it is energised by an electronic control unit. | |
PumpDevice that is electrically or mechanically driven to pressurize a fluid or gas. | |
PunctuationThe use of marks and signs to form words, sentences, paragraphs etc. | |
Purge ValveThe valve in a fuel vapour evaporative system operated from the ECM under specific conditions to draw air back through the evaporative canister. An emission control device to prevent hydrocarbon fuel vapours from the fuel tank escaping into the atmosphere. | |
Push FitThe relationship between the dimensions of two components where one fits inside the other. In this instance the fit is one where the inner dimension of the outer component is the same as the outer dimension of the inner component. Also known as a transition fit. | |
Push RodA rod that transfers movement from a cam follower to a rocker arm. | |
PWRPower to Weight Ratio | |
PyrotechnicExplosive devices! | |
Pyrotechnic InflaterAn explosive device used to produce a large quantity of gas to inflate an air bag. | |
Q |
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QCQuality control | |
QtQuart" | |
QuadralinkA four link suspension system developed by Ford. | |
QuadrantA mechanical lever shaped as a quadrant usually with three or more points for transmitting movement. | |
Quadrant and PinionMechanism to raise and lower window. Similar to rack and pinion but with the rack on the circumference of the quadrant. | |
QuadricycleFour wheeled vehicle with a max ULW of 400kg (550kg for a goods vehicle) with a max net power of 15KW. | |
Quarter Panel (Rear quarter)Side Panel which is generally a quarter of the total length of the vehicle and extends from the rear door to the end of the car. | |
QuartileAny three points that divide an ordered distribution into four parts. Each of these parts contain a quarter of the score. | |
QuartzA type of glass that will withstand very high temperatures. | |
Quartz Halogen LampHigh intensity light bulb with a quartz glass bulb and filled with a halogen gas. | |
QuenchingA process of rapid cooling. | |
R |
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RacistIntolerance of race. A person with prejudiced belief that one race is superior (better) than another. | |
RackGear teeth cut on a straight bar or rod. | |
Rack and PinionType of steering system gearing. | |
RadialOutwards from the centre and at right angles to the axis. | |
Radial (Tire)Tread supported by crown plies and casing plies laid radially. | |
Radial (Tyre)Tread supported by crown plies and casing plies laid radially. | |
Radial ForceA force that acts outwards from a centre point. | |
Radial GrooveA groove running radially, or radiating from the centre and around a component. | |
Radial PlayFree play at right angles to the axis. | |
Radial RunoutOut of true movement at the periphery of a rotating circular component. | |
Radial-pistonUsually refers to a pump where a number of pistons are used that act outwards from the centre. | |
RadiationThe emission and diffusion of rays. | |
RadiatorAn apparatus for radiating or diffusing heat. | |
Radiator CapCap used to pressurise cooling system. | |
RadiusThe straight line distance from the centre of a circle to any fixed point on the circumference. | |
Radius ArmSuspension link with a fixed inner bearing and support for the stub axle assembly at the outer end. | |
Rail(1) Gear selector component carrying the selector forks in a manual transmission. (2) Pressurised petrol supply tube for all fuel injectors in a port electronic fuel injection system. | |
RAMRandom Access Memory. Dynamic memory in computers which holds data being worked on. This data is not permanent and will be lost when power is switched off. | |
Ram Air EffectForced movement of air due to the movement of the vehicle. | |
Ram CylinderHydraulic cylinder that applies force to a rod. Often part of a steering system. | |
Ram PressurePressure caused by air of fluid movement. | |
RangeThe difference between the highest and lowest numbers. | |
Range Change(1) High and low gear ratios for an off-road or sport utility vehicle. (2) Secondary gearing in a large goods vehicle transmission gearbox that couples with the primary gears to double or treble the overall gear ratios. | |
Rare earth magnetsThese magnets are made from substances which hold a more dense magnetic flux than regular magnets. This means more power for the weight. Rare earth magnets are always preferable although not necessary as they can be expensive. | |
RatchetA mechanism consisting of a toothed wheel, the ratchet, and a locking or actuating pawl. Used to either prevent the pawl lever or the wheel from rotating in one direct only or in some mechanisms to drive the wheel forward. | |
RatioThe numerical relationship between two or more components transmitting a force or movement. | |
Ravigneaux Planetary GearsAn epicyclic gear set with two sun wheels and planetary gears on a common annulus. | |
Re-faceTerm used to describe the action when the face of a valve or other component is machined. | |
ReactTo respond. | |
ReactionAn equal and opposite force. | |
Reaction MemberThe held component of an epicyclic gear train that produces the specific gear ratio when held. | |
ReactorPart of a fluid flywheel that reacts to the movement of fluid. | |
Ready-To-SprayDescribes paint which has been properly mixed with all necessary components and is ready to apply to the substrate. A variation is 'Ready-for-Use' (RFU) which refers to material that is purchased ready to apply straight from the container. | |
ReamedAccurate cutting of a hole using a reamer. | |
ReboreRecutting of a cylinder bore to an oversize dimension to remove wear and or damage. The cylinder is then fitted with oversize pistons. | |
ReboundSuspension movement following compression of the spring when the energy of impact is released. | |
ReceiverDevice used to receive or pick up radio signals or similar. | |
Receiver/DrierPart of an air conditioning system in the high pressure side between the condenser and expansion valve that acts as a reservoir and as a filter and drier for the refrigerant. | |
RecessAn undercut area in a component usually machined to give access for a fixing or another component. | |
RechargingPutting back the electricity taken from a battery. | |
ReciprocalThe value of something when divided into one. The reciprocal of R is 1/R. | |
ReciprocatingMoving backwards and forwards. | |
Recirculating Ball SteeringA steering gearbox using the nut and worm principle. It has a series of ball bearings forming the thread of the worm, which gives a very smooth operation. | |
RecoatingThe application of fresh paint material over a recently painted material. | |
Recombinant BatteryA type of battery design which has slightly more negative plate material than positive plate material allowing the oxygen released by the positive plates, near to the fully charged position, to combine with the negative plate so that no gases are discharged. | |
RectifierAn electrical device that converts alternating current AC to direct current DC. | |
ReduceTo lower the viscosity of a paint by the addition of solvent or thinner. | |
ReducerA solvent used to reduce or thin paints to sprayable viscosity. | |
Reduction GearA gear (or more often pair of gears) used to reduce the speed of a shaft. | |
RedundantIn the context of systems or message transmission, redundant means extra information on say another channel that may not be used except for checking. | |
Reed RelayThin steel contacts that are joined when they become magnetic. The magnetism is created by a small coil, usually in series with a bulb. | |
Reed SwitchThin steel contacts that are joined when they become magnetic. | |
Reference VoltageA voltage value used in an electronic control module that is conducted to a sensor and against which the return voltage is measured in order to determine the signal value. | |
RefinishRepair of an OEM or previously painted substrate. | |
ReflectorBody or surface reflecting rays, particles, objects. Legal requirement on rear of vehicles. | |
RefractionDeflection at a certain angle when light enters obliquely from another medium of different density (light lens). | |
RefrigerantThe gas in an air conditioning system. It is condensed to a liquid by pressurisation and the heat in the refrigerant is taken in or passed out during the changes of state from liquid to gas and from gas to liquid. Two refrigerants are used for vehicle air conditioning. These are R12 and R134a. These must not be mixed or allowed to escape to the atmosphere. | |
Regenerative brakingA regenerative brake is an energy recovery mechanism that reduces vehicle speed by converting some of its kinetic energy and/or potential energy (due to elevation) into a useful form of energy instead of dissipating it as heat as in a conventional brake. | |
RegulatorAn electronic device for controlling the output voltage from a generator. | |
Regulator TerminalsTerminals on the regulator that connect to, for example, a warning light, field windings, sensing supply and ignition. Some also output signals to the engine management ECU. | |
ReinforceTo make information sink in. | |
Relative DensityThe ratio of the density of one substance to the density of water. Used to measure battery acid strength. Specific gravity is a similar but older term. | |
RelayElectromagnetic switch used in electric circuits to reduce load on smaller switches. | |
Relay CoilThe winding in a relay that when power is supplied to it, causes magnetism, which in turn makes the relay contacts close. | |
RelaysElectromagnetic switches used in electric circuits. | |
Release BearingShaft-mounted thrust bearing that transmits the action of the clutch pedal to disengage the clutch. | |
Release FingersThe fingers in a circular section of the diaphragm on a clutch that move when the release bearing is operated. | |
Release ForkThe actuating lever that moves the release bearing of a clutch. | |
Release LeversSee Release Fork. | |
Release MechanismComponents joining the clutch pedal to the pressure plate of the transmission clutch. | |
Release ShaftPivot for the clutch release lever. | |
Relevant InformationThe suitability of information based upon your needs. | |
Relief ValveSee Pressure Relief Valve. | |
ReluctanceA measure of resistance to magnetic forces. | |
REMCORemote adjustment for CO. | |
Remote StarterA switch, usually connected directly to the solenoid terminal of the starter motor, to allow remote operation during repair or testing. | |
Renewable resourceA natural resource is a renewable resource if it is replaced by natural processes at a rate comparable or faster than its rate of consumption by humans. Solar radiation, tides, winds and hydroelectricity are perpetual resources that are in no danger of a lack of long-term availability. | |
Replacement manual pagesReplacement pages are normally sent out under a Special Notice. They must be inserted into the manual immediately. Superseded pages should be removed. | |
ResearchTo study something thoroughly. | |
Reserve CapacityThe time for which a battery will produce 25A at 25C. | |
ReservoirA container holding a supply of liquid, gas, air or vacuum in a system. | |
Residual MagnetismThe magnetism held in an electromagnetic pole after the electrical current has been turned off. Natural magnetism in a magnet. | |
Residual PressureThe pressure held in a hydraulic line after a valve has closed and is used to reduce the pressure build up time when next applied. | |
ResilienceA property of material that has the ability to absorb energy from sudden loading by extension and resistance to fracture from stress loadings. | |
ResinA solid or semisolid material, usually polymeric, which deposits a film and is the actual film-forming ingredient in paint. Solutions of polymers are often called resins, but the term actually applies only to the film forming solids, not to the solution. | |
Resistance(1) Electrical resistance, the Ohm, is a measure of the opposition to electrical current flow in a conductor. (2) A force that acts in opposition to another. | |
Resistance TestA measurement of resistance using an ohmmeter. | |
ResistorElectrical device which has resistance to the passage of current. | |
Resistor PackSet of dropping resistors used as part of a heater motor circuit to set different speeds. | |
ResolutionThe number of pixels per square inch shown on the computer screen. The greater the resolution the better the picture. | |
Resonant FrequencyVibration at the natural frequency of a component. | |
Resonant NoiseA noise that results from vibration at the natural frequency of a component. | |
ResonatorComponent of the exhaust system to reduce noise. | |
ResourcesSources of information, expertise and knowledge. | |
RespiratorA device worn over the face to filter particles and fumes out of the air being breathed. Modern 2K paints require the use of air-fed respirators which provide an efficiently filtered supply of air at a positive pressure around a half-or full-face mask worn by the painter. | |
RestrictorA narrowing of a passage used to control flow of a gas or liquid. | |
Resultant ForceA force acting in one direction as result of other forces acting on an object from other directions. | |
RetarderA slow-evaporating solvent added to a paint to prolong the drying time. Typically used to reduce orange peel or blushing. | |
RetrofitThe fitting of a system after the vehicle has left the factory or later in its life. | |
RetrofittedRetrofitting refers to the act of adding new technology or features to older systems. | |
ReturnPipe or similar where, for example, fuel is returned to the tank. | |
Return SpringSimple spring to move an item back into its rest position. | |
RevcounterA tachometer that indicated revolutions per second. | |
Reverse BiasAn electrical term applied to semiconductors and transistors which normally allow the flow of current in one direction only but will allow current to flow in the opposite direction under specific conditions. | |
Reverse SwitchA switch operated by a gearbox component that illuminates the reverse light. | |
Reversing CircuitA circuit using changeover switches or relays that reverses the voltage supply to a motor. | |
ReviewTo look over and study information again. | |
RevisionTo review information in order to remind yourself of its content. | |
RFIRadio frequency interference. Electromagnetic radiation from an electrical source. | |
RfRReason for Rejection | |
RHDRight-Hand Drive | |
RheostatA type of variable resistor having only two terminals. | |
Rich Fuel/Air MixtureA fuel/air mixture with a ratio greater than the stoichiometric ratio of 14.7:1. A mixture strength with an excess of fuel. | |
RimOutside edge, periphery. Part of wheel carrying the tyre. | |
Ring Gear (Starter)A large diameter gear wheel mounted on the engine flywheel or torque converter flex plate and used to engage with the starter motor drive pinion to start the engine. | |
Ring GrooveSlot cut round the piston for the piston rings to sit in. | |
Ring LandSeating area for piston rings. | |
RIRORubbish In Rubbish Out. In relation to the Internet. | |
Road AdhesionGrip between the tyres and the road surface. | |
RockerA component such as a lever to operate a valve due to action of a cam. | |
Rocker ArmArm that works on a rocker shaft to open a valve on an overhead valve engine. | |
Rocker ShaftA shaft, usually at the top of an overhead valve engine, on which the rockers pivot. | |
Rocker SwitchA switch that has two or three positions. Often used with the centre as an off position and then with a voltage reversal process as it is rocked in either direction. | |
RollVehicle body movement from side to side. | |
Roller BearingA type of bearing consisting of a series of parallel rollers held in a cage between inner and outer bearing tracks. | |
Roller PumpA type of fuel pump that uses a rotor and a series of parallel rollers in an elliptical casing to produce the pumping and carrying chambers of the pump. Usually electrically driven and used on many fuel injection systems. | |
Roller-Cell PumpA type of fuel pump that uses a rotor and a series of parallel rollers in an elliptical casing to produce the pumping and carrying chambers of the pump. Usually electrically driven and used on many fuel injection systems. | |
Rolling ResistanceThe frictional value for the circumferential surface of a rolling component in contact with the track or road on which it runs. An example is the rolling resistance of a road tyre on various road surfaces. | |
Rolling RoadRollers set into the ground on which the wheels of a vehicle can be run. The system can then be used to check performance under driving conditions. | |
ROMRead Only Memory in a computer, which is the permanent memory that is retained even when the power is switched off. | |
RONRated Octane Number | |
RoofAdditional structural panel of vehicle body. | |
Roots SuperchargerType of mechanical pressure charger using two twin or triple lobed rollers to form an air pump in the inlet tract of an engine. | |
Rotary Air ValveA valve that uses a shutter to cover a hole depending on the amount of rotation. Usually used to refer to an auxiliary air valve on an injection system. | |
Rotary Control ValvePower steering control valve coupled to the steering column, which operates by inner and outer components coming together to open valve orifices to allow hydraulic fluid flow. | |
Rotary MovementCircular motion. Movement provided by the basic gear wheel or crank. | |
Rotary Oil PumpA positive displacement oil pump that uses two rotors inside a housing. There is an eccentrically driven rotor with eternal lobes that mesh with the internal lobes of a driven rotor. The external rotor has one more lobe than the internal rotor and this forms the pumping and carrying chambers of the pump. | |
Rotary PumpType of diesel fuel injection pump. | |
Rotoflex JointA propeller shaft universal joint using a sleeved hexagonal rubber ring between alternate three pointed couplings on each of the two connecting shafts. | |
RotorA component that rotates! Such as a brake disc, alternator rotor or oil pump rotor. | |
Rotor WindingsCopper windings that create the magnetic field on the alternator rotor. | |
Rounding OffExpress as a round number (i.e., 4.7 rounded off becomes 5) | |
RPMRevolutions per minute. | |
RSIRepetitive Strain Injury. This type of injury occurs from repeated physical movements. It can be caused by bad typing technique, bad posture and lack of adequate rest and breaks. RSI is common in the wrists. | |
RTVRoom temperature vulcanizing. A type of form-in-place gasket material. | |
Rub-throughThe result of sanding or buffing through one layer of paint and into the substrate below. A rub-through is common from clearcoat to basecoat or from primer to metal. | |
Rubber MountingsHard rubber connection units used to insulate one component from another to reduce vibrations and noise. | |
Rubbing CompoundAn abrasive that smoothes and polishes the paint film. Also known as polishing compound. | |
Run-outA measure of the out-of-true state on the face or faces of rotating components such as brake rotors and the clutch face on engine flywheels. | |
RunnerAn engine intake tube joining the plenum chamber to the inlet port in the cylinder head. | |
Running ClearanceA small gap between moving components that allows movement and lubrication. | |
Running OnThe term applied to an engine that continues to run after the ignition has been switched off. Also run on and dieseling. | |
RunoutA measure of the out-of-true state on the face or faces of rotating components such as brake rotors and the clutch face on engine flywheels. | |
RustThe corrosion product that forms on a steel surface when it is exposed to oxygen and water. Also known as oxidation. | |
RWDRear Wheel Drive. | |
Rzeppa JointA type of constant velocity joint used on vehicle transmission drive shafts. It has 6 steel balls in a cage between inner and outer elliptical housings. | |
S |
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S Classification (SAE)Engine oil suitable for gasoline engines. The second letter in the classification denotes the quality and minimum conditions that the oil must meet. | |
S.W.LSafe Weight Limit." | |
SAESociety of automotive engineers. SAE International is the premier membership society dedicated to advancing mobility engineering worldwide. SAE is a global technology information and standards organisation. | |
SaggingExcessive flow on a vertical surface resulting in drips and other imperfections on the painted surface. Can Occur not only when the paint is wet, but also during baking in certain types of paints. | |
SandTo smooth a surface with an abrasive paper or cloth. | |
Sandblasting (grit-blasting)A method of cleaning metal, usually steel, by applying an abrasive with pressurised air. This is a very efficient method of removing paint and corrosion prior to repainting. | |
SanderA power tool used with abrasives to roughen up or smooth surfaces quickly. | |
Sanding Block (Rubbing block)A hard, flexible block to provide a smooth, consistent backing for abrasive papers used in hand sanding. | |
Sandscratch SwellingExaggerated distortion of sanding marks in the underlying surface, usually caused by solvents in the topcoat attacking the substrate. | |
SandscratchesTracking in the topcoat of sanding marks in the substrate. Usually caused by either flatting with abrasives that are too coarse, or failure to adequately fill sanding scratches with primer fillers/surfacers | |
SatelliteThis can refer to any celestial body orbiting around a planet or star but usually means man-made equipment that orbits the Earth. | |
SatinA surface finish that is approximately half-way between gloss and matt | |
SaturationA term referring to a colour's purity or richness. The more chroma in a colour, the more saturated that colour is. | |
SAWSpark advance word output signal. | |
SCSupercharged | |
Scan ToolDiagnostic tool that connects to an electronic control module on a vehicle to read fault codes and other data. | |
ScannerDiagnostic tool that connects to an electronic control module on a vehicle to read fault codes and other data. Some scanners can also connect to controller area networks (CAN). | |
ScanningTo skim/scan text in order to get a general idea about it. | |
Scavenge PumpThe oil pump in the oil pan of a dry sump (oil pan) engine that returns the lubricating oil to a separate reservoir. | |
ScavengingThe process in the combustion chamber that clears the residual exhaust gases by the incoming air charge. The inlet and exhaust valves are both open for a very brief spell as the engine moves across top dead centre at the end of the exhaust stroke. | |
Schrader ValveA spring loaded valve for retaining the pressure in a tyre and to allow for tyre inflation. Fitted into the rim of a wheel either as a separate valve for tubeless tyres or as part of the tube for tubed tyres. | |
SciaticaNeuralgia of the hip and thigh. | |
ScopeShort for oscilloscope - Test equipment with a screen that can display electrical signals. | |
Scraper RingPiston ring that controls amount of oil on cylinder wall. | |
Screw ThreadA method of increasing force. | |
Scrub RadiusEffect on the tyre of steering turn. | |
ScuffingA rubbing wear due to lack of lubrication or incorrect alignment. Examples are cylinder scoring and tyre tread wear on one side of a tyre only. | |
SealOil, water or gas tight join. | |
Seal LandThe area on shafts that an oil seal lip seals against. | |
SealantA liquid material that is used with or, in place of, a gasket to give a gas or liquid seal. Sealants can be either fully setting and go hard after application or non-setting which remain flexible in use. The correct type of sealant should be selected. | |
SealerAn undercoat that enhances adhesion by providing a barrier between the underlying paint and the new paint. Provides uniform colour holdout and an even, level surface for topcoat application. | |
Sealing RingA rubber (or similar material) ring that fits in or against an item to make an air or liquid tight seal. | |
Sealing StripGasket to prevent leaks. | |
Search EngineA program that enables you to locate information on the World Wide Web using keyword searches. | |
SeatA machined face for making a good seal when matched with a valve. | |
Secondary BrakeBack up brake system, either mechanical or a split line hydraulic layout. | |
Secondary CellsThe cells of a rechargeable battery. | |
Secondary ShoeTrailing shoe in a drum brake. | |
Secondary WindingThe high tension (secondary circuit) coil of wire in an ignition coil. | |
SeedingThe development of tiny insoluble particles in paint (in the can) which results in a rough or gritty film. | |
SEFISequential Electronic Fuel Injection. | |
Seismic MassA small mass (weight) that moves to act as a sensing element. | |
SeizureLock up of mechanical parts preventing or restricting proper movement. | |
Selector ClutchPart of gear change system that automatically synchronises gear speeds before they are engaged. | |
Selector ForkA fork that acts on, and moves a gear selector. | |
Selector LeverAny lever to control a system that the driver uses to select a function. | |
Selector MechanismThe mechanical connection between the driver and the gearbox shift hubs in a manual transmission. | |
Selector ShaftSimple shafts that are attached to and move the selector forks, which in turn move the synchronisers. | |
Self TestSee Self-Test. | |
Self-AdjustingA mechanism or component that takes up free play automatically by either a mechanism or hydraulic pressure. | |
Self-diagnosticsA system where the ECU can determine if an error has occurs in its own inputs, outputs or systems. | |
Self-monitoringA system where the ECU can determine if an error has occurs in its own inputs, outputs or systems. | |
Self-Servo ActionDescription of how the leading shoe on a drum brake system is pulled by the drum such as to increase its braking effect. | |
Self-TestStart up and monitoring sequences for electronic control systems. Produce fault code data and triggers warning signals. | |
Semi Floating AxleAn axle hub arrangement with one bearing mounted inside the axle casing where it supports the axle shaft. The load is carried by the shaft which has shear and bending forces applied to it. | |
Semi-conductorA material that can be made to conduct or block electricity. A diode is a good example. | |
Semi-elliptical SpringA suspension leaf spring consisting of one or more leaves with mounting eyes or slippers at the ends and having a curved shape. | |
Semi-glossAn intermediate gloss level between high and low gloss. | |
Semi-trailing ArmA rear suspension type with a triangular trailing arm that has the chassis mounting points set at an angle to the transverse axis of the vehicle. | |
SemiconductorA material that can be made to conduct or block electricity. A diode is a good example. | |
Sender UnitAnother name for a sensor. | |
SensorElectronic components that send electrical signals to the ECU. | |
SensorsElectronic components that send electrical signals to the ECU. | |
SequenceOne thing that follows on to the next in time. | |
Sequential Fuel InjectionA petrol fuel injection system using ported injection timed in sequence with the engine firing order. | |
Sequential InjectionSee Sequential Fuel Injection | |
Serial Fault ReaderEquipment that connects, usually to the OBD plug or similar, to read stored faults in an electronic system. See also scanner. | |
Series CircuitAny electric circuit having all elements joined in a sequence such that the same current flows through them all. | |
Series hybridAn engine drives a generator which in turn powers a motor that drives the vehicle. | |
Series ResistorA resistor in a circuit that is connected in-line with the supply. | |
Serpentine BeltA single flexible drive belt that provides a drive from the engine crankshaft to all ancillary components. Replaces a series of individual belts. | |
ServoA servo mechanism (informal) | |
Servo CylinderRam cylinder that supplements physical forces in operating a control (as for example steering, a brake or clutch), either by direct mechanical amplification or by external power assistance. | |
ServomechanismSystem or device that supplements physical forces in operating a control (as for example a brake or clutch), either by direct mechanical amplification or by external power assistance. | |
ServomotorA motor that supplements physical forces in operating a control. | |
SESService Engine Soon (light) | |
SettlingGravity separation of one or more components from a paint and the resulting layer of material on the bottom of a container. | |
SFISequential Fuel Injection | |
ShacklePart of a leaf spring suspension system that allows movement (swinging shackle) or is fixed to the chassis (fixed shackle). | |
Shackle (Slipper)Allows for changes in length between the ends of a leaf spring as suspension moves. | |
ShadeVariation of a colour. A colour that is basically blue can have a red shade or yellow shade as well as being blue. Shade is also called tone or undertone, since it describes the subtle tone of a colour. | |
ShampooA cleansing agent consisting of soaps or detergents used for washing the hair – or a car! | |
SheenThe gloss or flatness of a film when viewed at a low angle. | |
Sheer ForceA force that tends to sheer or cut something much like the action of scissors. | |
Sheet Moulded CompoundFibreglass or thermoplastic plastic material moulded to shape and used as an outer panel on a vehicle. | |
Shell BearingsPlain bearing formed from two interlocking and abutting thin walled semi-circular cups. | |
Shift ForkA fork that acts on, and moves a gear selector. | |
Shift RingPart of a gear selector mechanism. | |
Shift RodA simple rod that connects the gear change lever to the gearbox. | |
Shift ShaftA shaft that is used as part of a gearshift / gear changing mechanism. | |
Shift TimingThe point at which an automatic gearbox changes gear. | |
ShimA thin metal sheet or washer used between two components to adjust free play. Shim material is produced in standard sizes. | |
ShimmySide to side movement of the wheels that causes the tyres to lose some grip on the road. | |
Shock AbsorberMethod of dampening suspension spring shock oscillation. Damper. | |
Short CircuitA short circuit is one that allows a current to travel along a different path from the one originally intended. | |
Short EngineEngine block containing crankshaft and pistons. Usually referred to when being replaced to overhaul the engine. | |
Short MotorThe engine block and crankcase together with all internal running components, pistons, crankshaft, etc. | |
Shrink FitAn interference fit obtained by heating the outer component or cooling the inner component so that they can be assembled with a push fit. When the temperatures are balanced the parts retain their interference fit. | |
ShrinkageLoss of solvent during the drying/curing process of a paint film. | |
ShroudGeneral term used to describe a cover. | |
Shunt (Electrical)A parallel part of an electrical circuit. An example is the shunt windings of some starter motors. | |
Side DraftA carburettor where the choke tube (venturi) is fitted horizontally. | |
Side ThrustForces caused by cornering. | |
Side-draught BoothA spray booth in which air movement is from the front to back. | |
Side-toneViewing the repaired area from an angle just past the reflection of the light source. | |
SiemensSiemens IT solutions and Services Ltd – Service provider for MOT Computerisation. | |
Significant FiguresThe number of digits expressed in a measurement. Sig. fig. can appear before and/ or after the decimal point. | |
Signposting Guidancewithin the specifications for the new AS levels A levels and GNVQs, opportunities for developing or producing evidence for assessment of key skills. | |
Silencer (Muffler)A component in the exhaust system to absorb the gas shock waves and noise in order to reduce the emitted noise from a vehicle engine. Also known as a muffler.(US term). | |
SiliconOne of many polymeric organic compounds of silicone with high resistance to cold, heat, water and passage of electricity. | |
SiliconeA chemical compound with excellent water repellency and a slippery feel. Silicones are commonly used in automotive waxes to enhance application and ease of removal, and to increase gloss and durability. The term 'Silicones' is often applied to the defect known as 'cratering' or 'fish-eyes' | |
Simple Gear TrainTwo or more gears in direct mesh. | |
SimulationSimulation is the imitation of some real thing, state of affairs, or process. The act of simulating something generally involves representing certain key characteristics or behaviours of a selected physical or abstract system. | |
SimulationsActivities that simulate or model reality. | |
SimultaneouslyTwo or more things happening at the same time. | |
Sine WaveThe wave pattern of an AC current. The positive and negative patterns are an inverse copy of each other. | |
Single Point InjectionA petrol fuel injection system using a single point injector in a throttle body in the inlet air supply and positioned on top of the inlet manifold. Also throttle body injection (TBI)." | |
SinkageA condition in which the topcoat appears to sink into the primer coat causing a loss of gloss. Also, a loss of gloss due to improper solvent selection. | |
SinteringA manufacturing process using heat and pressure to form metal and composite components. Examples are brake lining materials and some components traditionally produced by forging or hot stamping. | |
SipeVery narrow groove or cut in the tyre tread that aids the dispersal of surface water between the tyre and road. | |
SIPSSide Impact Protection System | |
SkidpanSpecial test track for skidding on! | |
Skim-readingTo skim/scan text in order to get a general idea about it. | |
SkinningThe formation of a thin, tough film on the surface of a liquid paint film, usually due to oxidation, hardening, or drying of the paint. | |
SLA SuspensionShort and long transverse suspension arms. The upper arm is the shorter of the two. The geometry of this layout keeps the wheel camber reasonably constant during suspension movements. Also known as 'unequal wishbones'. | |
Slave CylinderA hydraulic cylinder receiving a force and operating a mechanism. Examples are the clutch cylinder and the brake or wheel cylinders in brake units. | |
Sleeve (Cylinder)A steel sleeve used to form a running surface for pistons in an engine. Also known as a cylinder liner. | |
Sliding CaliperA brake caliper that has one piston and one sliding section. | |
Sliding JointA drive shaft joint with the ability to change length and to transmit movement usually with a splined construction. | |
Sliding ResistanceThe frictional value for the surface of a sliding component in contact with the track or road on which it runs. An example is the sliding resistance of a road tyre skidding on a road surface. The sliding resistance is usually less than the rolling resistance. | |
Slinger(1) A plate fitted on a rotating shaft in front of an oil seal to reduce the volume and pressure of the oil on the seal. (2) A plate or protuberance on a crankshaft for throwing oil onto the cylinder walls or other components. | |
SlipLoss of grip between two frictional faces. | |
Slip AngleThe difference between the true line and the actual line of a vehicle wheel when cornering. | |
Slip RingContinuous ring of copper used with a brush to transmit electricity through a rotating component. | |
Sludge (Oil)Lubrication oil deterioration where the oil thickens, mixes with contaminants and forms a thick and glutinous jelly or paste. | |
SludgingDescription of what happens to oil if it is not changed as recommended - a sludge forms that looks like Mississippi mud! | |
Smart CardA card issue to an authorised user to access the MOT database via the VTS Device. | |
Smoke MeterOpacity meter used to measure the amount of smoke in diesel engine exhaust gases. | |
SNSpecial Notice – an official notice issued from time to time by VOSA to inform AEs, NTs and other system users of changes to the testing scheme. SNs may also be used to highlight areas of concern and to advise of developments of the scheme. | |
Snail CamA cam that is shaped like a snail shell. In other words it has more effect the further it is turned. | |
SnatchingTerm used to describe the action of a clutch when the take up is too sharp/severe. | |
SOCState of charge (of a battery) | |
Sodium HydroxideA chemical used as the inflater for some air bags. | |
Soft Interface PadA support pad to which a finishing film abrasive disc can be attached. A soft interface pad reduces the pressure transmitted to the surface to be finished and moderates the cutting effect of the abrasive. Also used to great advantage on highly contoured surfaces. | |
Soft Jawed ViceA vice with soft material fitted to the jaws to prevent damage to any components held in it. | |
SoftwareA computer program. | |
SOHCSingle Overhead Camshaft Engine. | |
SolderA mixture of lead and tin used to join wires and terminals. | |
Soldered JointTermination of cables with solder. | |
SolenoidA coil of wire. Usually used to refer to a device containing an electromagnet. | |
Solenoid SwitchElectro-magnetically activated electrical switch. | |
Solenoid ValveA valve operated by a solenoid. Fuel injectors are good examples. | |
SolidsThe part of the paint that does not evaporate but stays on the surface to form a film. Usually measured on a weight or volume basis. | |
SolutionHomogeneous liquid or mixture of two or more chemical substances. | |
SolvencyThe ability of a liquid to dissolve a solid. Measured by the viscosity of a solution at a certain concentration of solid resin. The same solvent may have different solvency for different resins. | |
SolventA liquid which will dissolve another material, usually resins or other binder components. Commonly organic liquids. | |
Solvent DensityThe weight per unit volume of a solvent or solvent mixture. | |
Solvent-BlendThe particular mixture of liquids (usually true solvents and diluents) that give a paint the desired flow or evaporation properties. | |
Solvent-borneDescribes a paint which contains organic solvents rather than water as its primary liquid component. | |
Solvent-PoppingBumps or small craters that form on the paint film, which are caused by trapped solvent trying to escape through the drying paint. | |
South PoleThe term used to describe one of the poles of a magnet where the magnetic field lines of force end. | |
SpacerA metal sheet or washer used between two components to adjust free play. | |
Spade TerminalA flat blade terminal used to make an electrical connection. | |
Spark Ignition (SI)The ignition of petrol by a spark in the combustion chamber of an engine. | |
Spark PlugsUsed to provide a small gap in the combustion chamber of an engine, for a spark to jump across. | |
SpeakersDevice that converts audio signals to sounds that humans can hear. | |
Specific GravityThe ratio of the density of a substance to that of water. | |
Spell CheckerMost computer applications (i.e., Microsoft Word, Excel etc.) will enable you to check documents for incorrect spelling. | |
SpellingTo form a word with a series of letters. | |
SPISingle point injection. Electronic throttle body fuel injection system. | |
Spider1. Arachnid with eight legs...2. Name sometimes used for the shaft on which planet gears rotate in a differential. | |
Spider DiagramsA series of lines and boxes containing relevant information. A form of note taking. | |
SpigotA bearing between two shafts mounted end to end axially. | |
Spigot BearingBearing for a spigot shaft. Usually used to refer to the bearing inside the end of the crankshaft, into which the gearbox input shaft fits. | |
SpindleA rotating shaft. | |
Spindle Arm(1) Lever that imparts the steering action to the steering knuckle or stub axle assembly, as from a tie rod or track rod. Also steering arm, though this term is often used for the lever that imparts steering action from drag link to steering knuckle. (2) An intermediate arm in a steering system. | |
Spindle BushesSimple bearings on which a spindle rotates. | |
Spiral springThese are generally made of rectangular section material, flat strip, with round edges. They are general used as brush springs in D.C. motors. Also known as clock springs | |
Spirit LevelA device full of liquid with a bubble that moves to the centre when it is level. | |
SpliceA joint in two or more cables made by crimping or soldering the cables together. | |
SplineAxial groove on a shaft and hub. | |
Splined JointA toothed joint between two shafts that will transmit rotation but also allow axial (back and forth) movement. | |
SplinesAxial grooves on a shaft and hub. | |
Split PinA soft steel pin that has two sides that are folded out to secure the pin in a hole. Sometimes called a cotter pin. | |
Split RingsTwo continuous rings of copper used with brushes to transmit electricity through to a rotating component such as an alternator rotor field winding. | |
Split Slip RingTwo continuous rings of copper used with brushes to transmit electricity through to a rotating component such as an alternator rotor field winding. | |
SplitterTool used to split ball joints or track rod ends from the steering arms. | |
SpokesThin metal rods that join the wheel hub to the rim and support the weight of a vehicle. | |
Spongy (Brakes)Usually caused by air in the hydraulic brake lines. A soft and imprecise feel to the brake pedal. | |
Spot RepairA type of refinish job in which a section of the vehicle smaller than a panel is refinished. The paint is usually blended into the surrounding area. | |
SPOUTSpark output Signal. | |
Sprag ClutchA uni-directional rotary clutch that uses a series of shaped (like a figure 8) rollers and springs to either freewheel or grip the outer tracks to transmit a rotating force. | |
Spray BoothAn enclosure used to paint vehicles. Spray booths have controlled air flow and normally have temperature control or baking capacity. | |
Spray GunA device that mixes paint and compressed air to atomise and control the spray pattern as the paint leaves the fluid needle and air cap. | |
SprayingPaint is atomised in a spray gun and the stream of atomised paint is directed at the part to be painted. Atomisation is normally achieved using high pressure air, by high fluid pressure, or by electrical means as in an electrostatic process. | |
Spreader ValveThe adjustment valve on a compressed air spray gun which directs an air stream against the sides of an atomised paint cloud to adjust the spray pattern. | |
SpreadsheetA computer program often used to create financial forecasting documents. | |
Spring ClipSmall fixing device that can usually be removed by hand. | |
Spring EyeA hole formed at the ends of leaf springs to allow fixing to the chassis. | |
Spring RingSmall spring fixing device like a circlip. | |
SprocketsGear wheels usually used to drive or be driven by a chain. | |
Sprung Mass (Weight)The part of the vehicle supported by the suspension springs. | |
Spur GearA gear wheel with straight cut teeth. | |
Spurious DataData that falls outside what is expected. | |
Square MetreThe area enclosed by a square with sides of 1 metre long. | |
Square WaveThe wave pattern formed by a digital signal. | |
SquealHigh pitched noise (screech) from friction components. Examples are brakes, clutch and drive belts. | |
SqueegeeA flexible rubber blade used to wipe off excess water from washed or wet sanded areas. | |
SquirmA twisting or side-to-side movement. | |
SRIService Reminder Indicator. | |
SRSSupplementary Restraint System. | |
SRTSystem Readiness Test | |
SSSpeed Sensor | |
SSISolid State Ignition | |
Stabiliser BarA torsion bar that connects the suspension on each side of a vehicle's axle to transmit movement from one side to the other in order to reduce vehicle roll when cornering. | |
StabilizerAn additive included in a paint mixture to prevent degradation during storage. | |
Stall SpeedThe maximum engine speed (rpm) of a vehicle with automatic transmission that can be obtained at full throttle against the brakes without moving the vehicle. A test procedure to check the torque converter. | |
StallingWhen an engine stops because it is running too slowly or due to some other influence such as a learner driver! | |
StampingA manufacturing process using punches and dies to cut objects out of sheet materials. | |
Standard FormUsed so that very large or very small numbers can be written in a more convenient way. | |
Standards moderationThe means by which awarding bodies ensure consistency across centres and ensure that national standards are being maintained and applied. | |
Star Wound StatorAn alternator stator winding with the three-phase coils connected at the centre in order to give a large voltage output. The normal winding for light vehicle applications. Also 'Y' type stator. | |
Starter MotorA powerful electric motor that produces high torque to rotate the engine for starting. | |
Starter Solenoid FeedSmall wire that causes the solenoid to operate. Feed is from the starter switch and usually a relay. | |
Starter SwitchThe switch that operates the starter motor. Usually part of the ignition switch. | |
StaticA term that indicates components that are stationary. The opposite of dynamic when the components are in motion. | |
Static BalanceThe balance of a rotating component about the rotational axis. Wheel balance has both static and dynamic quantities. | |
StatisticsNumerical data. | |
StatorStationary part of machine. Examples are the magnetic inductance component of an alternator and the reaction member in a torque converter. | |
Stator WindingsElectrical windings on the stator of an alternator. | |
STCSelf-Test Connector. | |
SteelA ferrous metal commonly used as a substrate for paint, which must be painted to prevent corrosion. | |
SteeringMechanism or means whereby the direction of a vehicle is controlled. | |
Steering Arm(1) Lever that imparts the steering action to the steering knuckle or stub axle assembly, as from a tie rod or track rod. Also spindle arm (US), though this term is often used for the lever that imparts steering action from drag link to steering knuckle. (2) An intermediate arm in a steering system. | |
Steering AxisThe point about which the steered wheel turns. | |
Steering ColumnThe linkage and outer housing between the steering wheel and the steering gearbox/rack. | |
Steering GearSmall pinion that operates the steering rack. OR Worm gear that operates a steering arm. | |
Steering GearboxGearcase in which the rotary movement of the steering column is converted into angular motion of the drop arm or pitman arm. | |
Steering Geometry(1) Position of the wheel and steering swivel mountings. (2) Combination of angles in steering swivel. | |
Steering NutPart of a steering gearbox that moves on the worm gear. | |
Steering RackSystem where a small pinion works on a flat gear (rack) to move the steering arms. | |
Steering ShaftThe shaft that rotates as the steering wheel rotates. | |
Steering SwivelThe turning component that carries the steered wheel, king pin, stub axle assembly and McPherson strut. | |
StelliteHard and temperature resistant metal alloy used to coat exhaust valves. | |
Stepper MotorAn electrically controlled motor that gives precise incremental movements. | |
Stepper MotorsAn electrically controlled motor that gives precise incremental movements. | |
STFTShort Term Fuel Trim | |
STISelf-Test Input. | |
STOSelf-Test Output. | |
Stoichiometric RatioThe chemically correct ratio for air and petrol to achieve complete combustion. An air/fuel ratio of 14.7:1. | |
Straight Line SanderSander that uses a back-and-forth movement to sand a surface using sandpaper on its shoe. | |
StrainStrain is the amount of extension in size divided by the original length. | |
StrainerA mesh filter for basic cleaning of oil or fuel. Usually fitted in the oil pan or fuel tank. | |
StranglerAlternative term for a choke flap in a cold start device for a carburettor. | |
Strap WrenchA tool used to undo filters. A simple strap tightens around the filter to grip it securely. | |
Strap WrenchesSee Strap Wrench. | |
StratifiedTo form, arrange, or deposit in layers. This usually refers to the fuel air charge in a cylinder where the layer next to the spark plug is richer than the layers further away. used for lean burn applications. | |
Strength (of a pigment)The opacity and/or tinting power of the pigment. The measure of the ability of a pigment to hide or provide colour to a substrate. | |
StressStress is a measure of a force or load divided by the cross-sectional area of a material to which the force is applied (N/m2). | |
Striker PinPart of the door latch mechanism. | |
Strippable CoatingAlso called booth coating. A sprayed peelable film which is applied to the internal walls of spray booths to provide protection from overspray. When the coating becomes sufficiently contaminated, it is easily peeled or scraped away and replaced by a new layer of strippable material. | |
StroboscopicA flashing light. A strobe light is used to check and adjust ignition timing. | |
Stroke (Cylinder)The length of travel of the piston in the cylinder. Twice the throw of the crankshaft. | |
StrutTerm used to describe a suspension unit that operates telescopically. | |
Stub AxleAlternative name for a king pin assembly or steering swivel. | |
Stub Axle AssemblyAlternative name for a king pin assembly or steering swivel. | |
StudThreaded rod. | |
StyreneA low cost, colourless monomer which polymerizes readily. Widely used in the manufacture of fibreglass mouldings, plastic articles and polyester finishes. | |
Sub-FrameAn extra chassis component used to support a major part such as the engine or transmission. | |
SubstrateThe object or material to be painted. It may be bare metal, an old paint finish, or a foundation coating applied as part of a refinishing procedure. | |
Suction-feed GunA spray gun that has the paint container connected directly below it. Air flowing across the air cap creates a vacuum and, thus, draws the paint up from the container via a metal tube. | |
SumpLower part of an engine or gearbox usually containing lubrication oil. | |
Sun WheelCentral gear wheel of an epicyclic gear train or differential. | |
SunroofA fixed or operable (venting or sliding) opening in an automobile roof which allows light and/or fresh air to enter the passenger compartment. Sunroofs may be manually operated or motor driven, and are available in many shapes, sizes and styles. | |
SuperchargerA mechanical air pump driven from the crankshaft and used to boost the intake air charge for an engine. | |
SuperviseTo direct, manage, or oversee; to be in charge. | |
Supplied-Air RespiratorA respirator that provides safe breathing air to a painter while working with paints. The air supply provides not only breathing air but positive pressure on the edges of the mask to eliminate any contaminants from the outside air. | |
SuppressorAn electrical device fitted in parallel with a circuit to reduce the emission of electromagnetic waves at radio frequencies. | |
Surface plateA flat metal plate for gauging the accuracy of a plane surface in precision metalworking | |
SurfacerA heavily-pigmented foundation coating designed to be applied to a substrate for the purpose of smoothing or uniforming the surface for the subsequent coats of paint. Usually sanding is required, although non-sand variations are available. | |
SuspensionMeans whereby vehicle body is supported on its undercarriage, comprising springs, dampers and locating linkages. | |
Suspension ArmsLinkages used to construct a suspension system. | |
SVCService connector for octane and idle speed adjustment. | |
SwarfSmall pieces of metal that are produced during machining. | |
Swash-plate CompressorSee swash-plate pump. | |
Swash-plate PumpA type of pump that uses a rotating plate, that is radially off-set from the axis of the shaft, to operate the pump pistons in their cylinders. This design can also be used for compressors. | |
SWBShort Wheel-Base | |
Swept VolumeThe volume inside a cylinder above the piston crown at bottom dead centre minus the volume above the piston at top dead centre which forms the combustion chamber and is given the term 'clearance volume'. | |
Swinging caliperA type of floating caliper with wedge-shaped disc pads (only one of which is activated by hydraulic pressure from the piston, the other being fixed), which can pivot on its hinge pin to equalize the pressure on both pads | |
Swirl MarksA pattern of small scratches left in a finished surface by the wheel of a buffer or sander during the sanding and/or compounding operation, or by hand flatting using a circular motion. | |
Switch PackGeneral term to describe a collection of switches in one unit, window lift switches in the driver's door for example. | |
Swivel AxisLine about which the steering turns. | |
Swivel JointsJoints used as part of a steering linkage about which the steering turns. | |
Swivel PinsPins used as part of a steering linkage. Often called Kingpins. | |
SymmetricalA description of objects that are the same on each side of their centre line. | |
SymptomThe observed or measures result of a fault in a system. | |
Synchromesh GearGear change system in which the speed of rotation of a selected gear is automatically synchronized with that of the mainshaft. | |
Synchromesh HubCone clutches that are part of a gear change system which equalises the speed of a rotating gear. | |
SynchroniseTwo or more occurrences happening or being made to happen at the same time. | |
SynchroniserPart of gear change system that automatically synchronises gear speeds before they are engaged. | |
SynchronizationAn adjustment that causes something to occur or recur in unison. | |
SynchronizerPart of gear change system that automatically synchronizes gear speeds before they are engaged. | |
SyntheticPrepared or made artificially, in contrast to naturally. For example, synthetic engine oil is NOT made from crude oil! | |
T |
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T-PieceSimple connection device to allow a pressure gauge, for example, to be connected into a pipe or fuel line. | |
TACHTachometer | |
TachometerA meter for measuring the speed of rotation of a component or device. Used to describe the on and off vehicle instruments that measure engine speed. | |
TackThe stickiness of a paint film or an adhesive. The time it takes for an air-drying paint to reach a tack-free state. | |
Tack Cloth or RagA cloth coated with a non-contaminating sticky substance used to remove dirt and lint prior to painting. | |
Tack Coat (grip coat)The first sprayed coat of colour, applied lightly and allowed to flash-off only until it is quite sticky. | |
Tack-free TimeAn indicator of a coating's hardness development. The surface of the film will not finger mark, yet the film is still not dry and hard throughout. | |
Tandem Master CylinderA brake master cylinder with two separate pumping chambers. Used for split circuit brake hydraulic systems. | |
TangA projection or lug used to hold or drive an attached part. Tang on a file to hold the handle. | |
Tank SenderA unit in the fuel tank that indicates the fuel level. | |
TapA tool to cut internal threads. Cutting internal threads. | |
Tape TrackingMarkings left behind on a new paint film when masking tape was applied before it was hard enough to resist pressure marks. | |
TaperReducing in size along the axis of an object. | |
Taper Roller BearingA type of bearing consisting of a series of tapered or conical rollers held in a cage between inner and outer bearing tracks and able to carry thrust (axial) loads as well as radial loads. | |
TappetA valve lifter or cam follower in the engine valve gear train. | |
Tapping SizeThread core diameter, a drilling size. | |
TBThrottle Body | |
TBIThrottle Body Injection. | |
TCTurbocharged | |
TCCTorque Converter Clutch | |
TCMTransmission or Transaxle Control Module | |
TCSTraction control solenoid (SAAB 9000) | |
TDTurbo Diesel | |
TDCTop dead centre. The position of the crankshaft when the piston is at its highest position in the cylinder. The crankshaft is at 0° of rotation. | |
TDITurbo Direct Injection (A turbo charged direct injected diesel engine) | |
TDMATime Division Multiple Access refers to a digital communication link where multiple devices share a single carrier frequency by taking turns. Each gets the channel exclusively for a certain time slice, and then gives it up while all the other phones take their turn. | |
TelescopicActing like a telescope in having a sleeved construction where one or more sleeves slide inside the outer sleeve. Modern shock absorbers and safety steering columns are generally of this type of construction. | |
TemperatureA measure of the hotness or coldness of matter. The S.I. unit of temperature is the Kelvin (K) and is the same as minus two hundred and seventy-three degrees Celsius. | |
Temperature DifferentialDifference in temperature between two components. | |
TemperingBaking of plastic parts to drive off internal mould release agents prior to painting. | |
TensionForce due to a pulling effort. | |
Tension RodA trailing strut or rod positioned between the vehicle chassis and a suspension track control arm to hold it in position and to transmit driving and braking forces. | |
Tension/TensileOpposing pulling forces (tension) that create a stress (tensile) in an object. | |
TensionerA device usually consisting of a small pulley to set belt tension. | |
TerminalsElectrical connection points. Common types are described as spade, blade, ring and fork. | |
Test CycleStrictly controlled test procedure for exhaust emission evaluations. | |
Test LampA simple bulb used for tracing circuit faults. | |
Test PortA point where a test gauge may be connected. | |
Test ProbeA general term used to describe the device used to make contact when testing a circuit. The prods on the end of multimeter leads are good examples. | |
Test RigsMachines designed to allow components to be run and operated as if fitted to the vehicle. Used for test and calibration purposes. | |
Tetraethyl LeadA petrol additive to reduce 'knock' or detonation. Also described as an octane enhancer. | |
TFIThick film ignition module. | |
Theoretical CoverageDescribes a paint's film thickness or hiding power. Defined as the number of square metres a coating should cover at a specified film thickness measured in microns. | |
Thermal CyclingLaboratory testing of paint formulations by alternately heating and cooling a painted object to determine what effect this variation has on the paint's properties. | |
Thermal EfficiencyThe ratio between the heat energy in the fuel and the power output from the engine. | |
Thermal ExpansionIncrease in size of an object as temperature increases. | |
Thermal GaugeInstrument gauges that use the heating effect of electricity to move a needle. | |
ThermistorResistor whose resistance is greatly reduced by heating. | |
Thermo Time SwitchA device containing a bimetal strip. It is used in conjunction with a cold start injector to deliver a set amount of extra fuel when starting from cold. | |
Thermo-time-switchA device containing a bimetal strip. It is used in conjunction with a cold start injector to deliver a set amount of extra fuel when starting from cold. | |
ThermoplasticA type of polymer paint or plastic which softens and melts when heated and then re-solidifies upon cooling. An example is 1K acrylic lacquer paint. | |
ThermostatTemperature sensing valve controlling flow of coolant. | |
Thermostatic ControlA device that uses temperature for actuation. | |
ThermosyphonThermosyphon (or thermosiphon) refers to a method of passive heat exchange based on natural convection which circulates liquid without the necessity of a mechanical pump. | |
Thick Film Ignition ModuleAn integrated circuit ignition control module." | |
ThinnersSolvent added to a paint to reduce its viscosity to a sprayable consistency. | |
Third PartyAnother party, not one's self (legal). | |
Thread PitchDistance from the top or peak of one thread to the top of the next. | |
Threaded UnionsUsually pipe connections using threaded connections. | |
Three Phase Electric CurrentThe internal alternating current output from an alternator stator and made up from three single phases starting at 120 degree intervals. The three phases are rectified to a direct current output for charging the battery and supplying the vehicle electrical systems. | |
Three Point Seat BeltType of seat belt that has a single belt threaded across the lap and shoulder and anchored at three points. The anchorage points are both sides of the lap and on the pillar above the shoulder of the wearer. Also known as a lap and diagonal belt. | |
Three Point StaticType of seat belt with lap and diagonal webbing. | |
Three Quarter Floating AxleAn axle hub arrangement with one bearing mounted in a hub on the axle casing. Although the load is carried mainly by the hub there are shear and bending forces applied to the axle shaft. | |
Three Way ConverterA dual bed catalytic converter with one stage coated with platinum and palladium and the other with platinum and rhodium. Converts HC (Hydrocarbons) and CO (Carbon Monoxide) to H (Hydrogen) and CO2 (Carbon Dioxide); and NOX (Nitrogen Oxides) to N (Nitrogen) and O (Oxygen). | |
Three-lobe CamA triangular shape cam. | |
ThrottleThe engine speed control mechanism operated by the driver. | |
Throttle BodyA simple unit containing a throttle butterfly. Use as part of an injection system. | |
Throttle Body InjectionA petrol fuel injection system using a single point injector in a throttle body in the inlet air supply and positioned on top of the inlet manifold. Also single point injection (SPI). | |
Throttle ButterflyThe restrictor (plate) in the air intake of petrol injection ducts or carburettors. | |
Throttle PlateThe restrictor (butterfly) in the air intake of petrol injection ducts or carburettors. | |
Throttle Position SensorSensor for throttle position information to engine management system. | |
Throttle PotentiometerA variable resistor that is moved with the throttle to allow position of the throttle to be sensed. | |
Throttle PressureShift control pressure in an automatic transmission regulated by engine speed and load conditions. | |
Throttle SpindleThe shaft on which the throttle butterfly moves. | |
Throttle SwitchA switch that operates when the throttle is fully open or fully closed. | |
Throttle ValveA valve in an automatic transmission that responds to throttle position or inlet manifold vacuum to regulate the throttle pressure. | |
Throttle/AcceleratorThe engine speed control mechanism operated by the driver. | |
Throttling BoreA fixed size orifice used to control or restrict flow. | |
Through- CureThe completion of the curing process at which no further chemical reaction can occur to aid in film formation. | |
ThrowThe dimension from the centre axis of the crankshaft to the centre axis of the big end bearings. | |
ThrustForce acting on an object causing it to change position or alignment with another object. Also used to describe a force along an axis where two components are forced together. | |
Thrust BearingBearing intended principally to react to axial or thrust loads. Thrust race (Informal). | |
Thrust Face (Piston)The side of a piston pressed against the cylinder wall during the combustion stroke. The opposite side to the connecting rod direction of travel. | |
Thrust PlateA plate that applies thrust (force). | |
Thrust PlatesPlates used to apply thrust (pushing force) to another component. | |
ThyristorA silicon controlled rectifier used as a switching device using a very low control current to switch much larger currents. Thyristors are switched on by a gate control current and remain on until the main current flow ceases. | |
Tick OverRotational speed of an engine on no-load and minimum throttle setting. Also idle or curb idle. | |
Tie RodA connecting rod in a steering system between the drop arm (Pitman arm), the idler arm and the steering arms on the steering swivels. | |
Time LagA delay in operation. | |
TimelinessReference to the time that information was recorded. | |
TimingRelative crankshaft rotational points of action within the engine operating cycle particularly for ignition and valve opening. | |
Timing BeltA toothed drive belt that droves from the crankshaft pulley to the camshaft. In some cases the drive is also to an ignition distributor or diesel injection pump. | |
Timing ChainChain that drives the camshaft from the crankshaft. | |
Timing MarksMarks on the crankshaft pulley, flywheel, distributor drive pulley and/or camshaft pulley. Used to accurately time and an engine. | |
TintAn individual pigment from a family of pigments used on a mixing machine to produce a colour match to the vehicle to be painted. Also refers to the act of colour adjustment where small amounts of tinters are added to mixed colour to correct a mismatch | |
Tinting StrengthThe ability of a pigment to change the colour of a paint to which it is added. Some pigments have high tinting strength and only a small amount is necessary to make a large change in colour. | |
TiresTires (or 'tyres' in British English) are ring-shaped parts, either pneumatic or solid, that fit around wheels to protect them and enhance their function. | |
Titanium DioxideA non-toxic, non-reactive, white pigment. Has the greatest hiding power of all white pigments. | |
TIVThermactor Idle Vacuum Valve | |
TKSThrottle Kicker Solenoid | |
Toe (Wheel Alignment)The relative angle of the road wheels to the true longitudinal axis of the vehicle. The toe angle is the degree of variation needed to bring the wheels into true rolling motion when the vehicle is travelling. | |
Toe InBasic setting of the road wheels on one axle when adjusted so that the front edges are angled very slightly inwards. Free play in the steering gear or suspension arms is taken up during forward motion to bring the wheels to a parallel position. | |
Toe OutBasic setting of the road wheels on one axle when adjusted so that the front edges are angled very slightly outwards. Free play in the steering gear or suspension arms is taken up during forward motion to bring the wheels to a parallel position. | |
Toe Out On TurnsThe difference between the angles of turn of the steered wheels when cornering. The angles are measured at 20 degrees for the inner wheel when checks and comparisons are being made. The outer wheel angle should be less than the inner wheel. | |
ToleranceThe amount that any dimension can be from the nominal size. | |
TolueneA widely used solvent or diluent or a co-solvent. (Co-solvents are used to help make sure the paint forms a tough, durable film). A fast-evaporating, high solvency, aromatic hydrocarbon. | |
Tone DiscA metal disc that sets the tone (frequency and volume) at which a horn operates. | |
Top CoatThe final layer of paint applied to a substrate. Several coats of topcoat may be applied in some cases. | |
Top Dead CentreThe position of the crankshaft when the piston is at its highest position in the cylinder. The crankshaft is at 0° of rotation. | |
TopcoatPaint for appearance and weather seal. | |
Topping OffTopping up. | |
Topping UpProcess of making sure a fluid is full to the top or appropriate level marking. | |
TorqueRotary or turning force. The SI unit of torque is Nm. The force in Newtons multiplied by the distance in metres. | |
Torque ConverterA fluid flywheel with a stator that creates a back force in the turbine that is added to the force from the impellor to give an increase in output torque. | |
Torque SettingsValues recommended by a manufacturer, to which certain fixings should be tightened. | |
Torque WrenchA calibrated wrench that allows tightening and adjustment of fasteners to a specified torque setting. | |
Torque-to-yieldType of bolt used for holding cylinder heads. They are made from a steel alloy that allows a tough hold down force at the yield point of the material. These bolts usually require tightening by an angular value and replacement whenever they are removed. | |
TorsionA twisting force that results in torsional stress. | |
Torsion BarMetal spring used in vehicle suspension. Uses a twisting action along the length of the spring to provide suspension movement. | |
Torsion SpringsA spring that works by twisting. | |
Torsional StrengthAbility to withstand rotational force. | |
Torsional StressThe stress that occurs when twisting forces are applied. | |
TorxTrade name for a hexagonal/star shaped tool that has extra machined slots for a better grip. | |
Total DisplacementApplied to the sum total of the swept volumes for all cylinders in an engine. Also known as 'engine capacity'. | |
Touch-upCorrecting minor scratches, stone chips, etc., usually by the use of a small brush. | |
Toughened GlassSoft glass with tough outer skin produced by heat treatment tempering. | |
Towing SocketA multisocket used to make electrical connections to a trailer. | |
TPThrottle Plate. | |
TPITuned Port Injection | |
TPPThrottle Position Potentiometer | |
TPSThrottle Position Sensor. | |
TPTThrottle Position Transducer | |
Track (Wheel)The dimension between the centres of the road wheels on one axle. Also known as tread. | |
Track Arm (Track Control Arm)A transverse lower suspension arm attached to the chassis at the inner end and to a McPherson strut at the outer end. Maintains the wheel track position and transmits transverse forces. | |
Track RodTransverse rod that connects the steering arms of steered wheels and so maintains the geometric relationship between them when steering. | |
Track Rod EndA ball joint coupling on steering track rod ends that join the track rod to another component to allow a range of angular movement. | |
TrackingIn electrical terms it is the loss of an electrical current outside of an insulator. The term is also used to describe the setting procedure for adjusting front wheel steering alignment. | |
TractionThe grip of the tyre with the road surface. The 'grip' can be specified as a coefficient of friction where the higher the number the greater the ability to transfer a force. (1 represents 100% for all force loads, tyres are generally in the range 0.75 to 0.85). | |
Tractive EffortThe forward force of a vehicle while it maintains tyre contact with the road surface. | |
Trailing ArmA suspension link or rod that carries an axle behind the mounting and pivoting point of the arm. Semi trailing arms are mounted at angle to the longitudinal and transverse axes of the vehicle. | |
Trailing EdgeThe back edge of a brake shoe in relation to the direction of rotation of the brake drum. | |
Trailing ShoeA brake shoe that has a trailing edge making first contact when applied. | |
Transaxle(1) Rear axle assembly that incorporates the main change-speed gearbox. (2) Combined gearbox and final drive unit attached to the engine in some front wheel vehicles. Contraction of transmission-axle. | |
Transaxle Gearbox(1) Rear axle assembly that incorporates the main change-speed gearbox. (2) Combined gearbox and final drive unit attached to the engine in some front wheel vehicles. Contraction of transmission-axle. | |
TransducerAn electronic device that converts a minute amount of one form of energy to another. A moving wheel with a tooth pattern can induce a voltage in a coil of wire around a magnet. This arrangement is used for speed and position sensors. Other transducers are used for other sensor applications. | |
Transfer BoxThe gearbox that splits drive front and rear for four wheel drive transmissions. | |
Transfer Box/CaseThe take-off gearbox for four wheel drive transmissions. | |
Transfer EfficiencyThe measure of paint material applied compared to the amount of material originally sprayed. Modern HVLP spray guns are expected to achieve a transfer efficiency of at least 65% | |
Transfer PortThe port that connects the crankcase to the cylinder on a two stroke engine and is used to pass a new air/fuel charge to the cylinder when the piston descends to bdc. | |
TransformerTwo coils or windings that interact to step voltage up or down. | |
TransistorsSemi-conductor devices with three electrodes. Electronic switches and amplifiers. | |
Transition FitThe relationship between the dimensions of two components where one fits inside the other. In this instance the fit is one where the inner dimension of the outer component is the same as the outer dimension of the inner component. Also known as a push fit. | |
Translucent/TranslucencyAllowing light, but not detail to pass through. Semi-opaque | |
Transmission(1) (US: gearbox) Mechanical unit containing a manual or automatic change speed gear system and associated actuating machinery. (2) (UK) Collective term for the components, such as clutch, gearbox, drive shaft, whereby power is transmitted from engine to driven wheels (mainly UK usage). | |
Transmission FluidThe oil used in a transmission system - several types are used so always check data. | |
Transmission RatioUsually used to describe the overall ratio of the transmission - from the engine to the wheels. | |
TransmitterDevice that outputs a signal, usually a radio signal (TV or radio transmitter) but in some cases wires are used (temperature transmitter for example). | |
Transparent/transparencyClear/clarity; Allowing light and detail to pass through; Not opaque. | |
TransverseAny axis running across a vehicle or other object at right angles to the longitudinal axis. | |
Transverse AxisAny axis running across a vehicle and parallel with the ground and at right angles to the longitudinal axis of the vehicle. | |
Transverse EngineAn engine fitted across the axis of a motor vehicle. | |
TrapezoidalA trapezoid (in North America) or trapezium (in Britain and elsewhere) is a quadrilateral two of whose sides are parallel to each other. Some authors define it as a quadrilateral having exactly one pair of parallel sides, so as to exclude parallelograms. It is the shape made by the linkages in an Ackerman steering system. | |
Tread (Tire)The surface of a tire that contacts the road surface and is cut to aid traction and dispel moisture. | |
Tread (Tyre)The surface of a tyre that contacts the road surface and is cut to aid traction and dispel moisture. | |
Tread (Wheel)The dimension between the centres of the road wheels on one axle. Also known as track. | |
TremblerA switch that is operated by movement of a vehicle. Used in alarm system. | |
Tri-coatA basecoat, followed by a transparent or translucent mid-coat, followed by clearcoat; to provide a special colour effect on the vehicle. | |
Tri-pod (Tri-pot) JointA constant velocity joint consisting of three drive pins and balls set in three axial tracks. | |
Trickle ChargeA very slow charge rate for a battery. Usually 1 or 2A overnight. | |
Trim HeightA measurement taken from a fixed point on the vehicle body to the centre of the wheel. | |
Trip ComputerA computer built in to some vehicles. It allows the display of different values such as average fuel consumption and estimated time of arrival at a destination. | |
TrunionA pivoting assembly consisting of a rod and bearings. | |
TrunkingGeneral name for large pipes or tubes usually used to carry air. | |
TSPThrottle Solenoid Positioner | |
Tuned Intake Pressure ChargingA system of intake air management that maximizes the flow of air into an engine by using the reciprocating air resonance in the manifold at different engine speeds. | |
TungstenSteel grey heavy metallic element with very high melting point. Used for light bulb filaments. | |
TurbineThe driven member in a turbocharger, turbine engine and torque converter. The turbine consists of a set of blades on a central boss and shaft and is driven by exhaust gases in a turbocharger or turbine engine and by liquid from the impeller in a torque converter. | |
TurbochargedEngine with a turbocharger, which is an exhaust driven device that pumps in extra air. | |
TurbochargerAir supply pressure charger driven by the engine's exhaust gas flow. | |
Turn angle sensorA device that measures and outputs a signal proportional to the angle that a vehicle is turning. | |
Turning CentreAn imaginary point about which a vehicle turns when cornering. Also known as the instantaneous centre of turn or rotation. | |
Turning Circle/RadiusThe minimum circle or radius in which a vehicle can turn when on full steering lock. | |
TVThrottle Valve | |
TVSThermal Vacuum Switch | |
TWCThree way catalyst. | |
TWC+OCThree Way + Oxidation Catalytic Converter | |
Twin Choke CarburettorA carburettor with two venturis either acting together or progressively. | |
Two Stroke CycleAn engine operating on two strokes of the piston. Induction occurs in the crankcase below the piston on the upstroke and is transferred to the cylinder at the end of the down stroke. Compression takes place above the piston on up stroke. The combustion and exhaust strokes occur above the piston on the down stroke. | |
Two-component System (2K)Materials such as paints, fillers, and adhesives which require the addition of a hardener or activator to accomplish a chemical reaction, causing them to cure. | |
Two-toneTwo different colours on a single paint job. | |
TyresTyres (or 'tires' in American English) are ring-shaped parts, either pneumatic or solid, that fit around wheels to protect them and enhance their function. | |
U |
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U BoltsU shaped bolts used to fix leaf springs to the axle or other similar tasks such as fixing a steering rack to the body. | |
U/JUniversal Joint. | |
Ultra VioletA frequency of light that is above the visible spectrum. | |
UltravioletLight/Radiation lying in the ultraviolet range; wave lengths shorter than light but longer than X rays i.e. beyond the violet end of the spectrum/rainbow. | |
Ultraviolet (UV) LightThat portion of the spectrum which is largely responsible for the degradation of paints. It is invisible to the eye and may also be referred to as "black light." Special UV lamps can be used to cure some paints and adhesives. | |
ULWUnladen Weight – The weight of a vehicle inclusive of the body and all parts which are ordinarily used with the vehicle when working on a road. Unladen weight does not include the weight of water or fuel used for the propulsion of the vehicle, | |
Unburned HydrocarbonsEngine or fuel tank emissions in the exhaust gas, fuel line vents or lubricating oil vapours. Harmful to health. Also HC or THC (total hydrocarbon content of exhaust gas). | |
Under-bakeThe result of curing a paint film at too low a combination of time and temperature. The film may be too soft for good durability. | |
UndercoatA first coat; primer, sealer, or surfacer applied to the substrate. Frequently used to provide corrosion protection and adhesion. | |
UndersteerSteering condition of a turning vehicle when the vehicle attempts to turn by a lesser degree than the steered position taken by the driver. This condition is usually provided by vehicle design in order to improve the driveability of the vehicle. | |
UnderwrittenSign and accept liability (legal). | |
Unequal WishbonesSuspension type with an upper wishbone shorter than the lower wishbone. The geometry of this layout keeps the wheel camber reasonably constant during suspension movements. Also SLA suspension. | |
UnidirectionalMove in one direction only. | |
Unidirectional ClutchA clutch, used in starter motors for example, to only allow drive to pass in one direction. | |
Union NutA hollow nut used to secure hydraulic pipes. | |
Unit-body ConstructionVehicle body and chassis constructed as a single unit. As distinct from a separate chassis and body construction. Also unitary body construction. | |
Unitary Body ConstructionVehicle body and chassis constructed as a single unit. As distinct from a separate chassis and body construction. Also unit-body construction. | |
Universal JointsRotating shaft coupling that permits angular axial displacement. Some types will also operate with linear misalignment of axes. | |
UnladenNot carrying a load. | |
Unleaded PetrolPetrol without any added lead to improve the octane rating. | |
Unsprung MassThe part of the vehicle not supported by the suspension springs. The road wheels, hubs, brakes and part of the suspension system. | |
Unsprung Mass (Weight)The part of the vehicle not supported by the suspension springs. The road wheels, hubs, brakes and part of the suspension system. | |
Up DraftA carburettor where the choke tube (venturi) is fitted vertically and the air enters from the bottom. Upwards movement of air. | |
Upper BeamThe upper of the two headlamp beams. Also driving beam and main beam. | |
Upper Control ArmThe upper and shorter wishbone in an independent suspension system. | |
Upper QuartileData is split into 4 equal quarters. The highest quarter is referred to as the Upper Quartile. For example the Upper Quartile of 100 is the highest 25 of the numbers. | |
UrethaneA type of paint or polymer which results from the reaction of an isocyanate with a hydroxyl containing component. Urethanes are noted for their toughness and abrasion resistance. | |
USA United States of America: North American republic containing 50 states - 48 states in North America plus Alaska in northwest North America and the Hawaiian Islands in the Pacific Ocean; achieved independence in 1776. | |
UVUltra violet. | |
UV StabilizersChemicals added to paint to absorb the ultraviolet radiation present in sunlight. Ultraviolet radiation decomposes the polymer molecules in a paint film and thus UV stabilizers are used to prolong paint life. | |
V |
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VVolts | |
V BATTBattery voltage. | |
V BeltA continuous loop drive belt with a 'vee' section. The sides of the belt grip the side faces of 'vee' pulleys to provide a friction drive method. | |
V PWRPower voltage. | |
V-beltA continuous loop drive belt with a 'vee' section. The sides of the belt grip the side faces of 'vee' pulleys to provide a friction drive method. | |
V.I.NVehicle Identification Number." | |
V(ref)Reference voltage. | |
V5/V5CVehicle log book/registration certificate. Issued by the Driver and Vehicle Licensing Agency. | |
VACVacuum | |
VacuumIn everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its pressure is much less than atmospheric air pressure. The word comes from the Latin term for empty. | |
Vacuum AdvanceAutomatic engine ignition timing adjustment using the inlet manifold pressure to sense engine load. The pressure, as a vacuum, is applied to a diaphragm assembly to move the base plate in the ignition distributor. | |
Vacuum Assisted BrakesA brake booster system that uses inlet manifold vacuum in a brake servo unit to increase the driver's braking effort. The vacuum can also be provided from a vacuum pump on diesel engines. | |
Vacuum GaugeAn instrument for measuring pressure (below atmospheric pressure) of a fluid or a gas. | |
Vacuum MotorA motor that is operated by a vacuum such as to move or drive something. | |
Vacuum PipesSee Vacuum Hoses | |
Vacuum PumpTest equipment that can be used to apply a vacuum. | |
Vacuum RegulatorA device that either controls vacuum so a set level or one that uses vacuum to regulate another operation. | |
VAFVane Air Flow Sensor. | |
ValencyTerm describes a material that has a free electron. | |
ValetingThis is the performance of an extremely thorough cleaning, polishing and waxing of an automobile, both inside and out, to produce a showroom-quality result. | |
ValueThe degree of darkness or lightness of a colour. | |
ValveA control device that restricts or cuts off the flow of a liquid or gas. | |
Valve BallA ball used to create a seal inside a valve. | |
Valve BlockCollection of valves in one unit that operate a common system (automatic transmission for example). | |
Valve BounceBounce of a valve in its seat when closing. Usually occurs as a result of the engine speed being too high or the valve spring losing tension through age or deterioration. | |
Valve Gear (Train)The mechanism from a cam to a valve in an engine that transmits the movement of the cam to open the valve. | |
Valve GuideThe tube or sleeve in the cylinder head that locates a valve centrally in its seat. The valve slides in the guide during opening and closing. | |
Valve HeadThe top or disc end of a valve that seals the gases in the cylinder head. | |
Valve LagThe term applied to valves which remain open after the piston has passed tdc or bdc at the end of a stroke in the four stroke cycle. | |
Valve LeadThe term applied to valves which open before the piston has passed tdc or bdc at the beginning of a stroke in the four stroke cycle. | |
Valve LifterCam follower or tappet. | |
Valve MarginThe thickness of the valve head between the valve face and the head surface. | |
Valve NeedleThe control pin in, for example, a fuel injector. The needle works against an accurately shaped component to control flow. | |
Valve OverlapThe term used to describe the angle of crankshaft rotation when the inlet and exhaust valves are both open. | |
Valve SeatThe bevelled surface annular face in the cylinder head that closes each port and into which a valve seats and seals the port. | |
Valve Seat InsertA steel insert fitted in aluminium and some iron cylinder heads to form a durable seating for the inlet and exhaust valves. | |
Valve SpringThe spring that closes and holds closed the valve. It fits around the valve stem above the guide and between the cylinder head and valve spring retainer. | |
Valve StemThe shaft of a valve. | |
VaneA flat component used as part of a pump that moves a liquid or fluid. | |
Vane PumpA type of positive displacement pump formed by an eccentric rotor driving two or more vanes fitted inside a housing. The eccentricity of the rotor and vanes forms the pumping chambers of the vane pump. | |
VaporSee Vapour. | |
VaporisationFuel that is broken down to very fine particles and distributed into the intake air stream of an engine. | |
VaporizationFuel that is broken down to very fine particles and distributed into the intake air stream of an engine. | |
VapourMinute airborne droplets of a liquid or liquid that has been heated to a gas state. | |
Vapour LockVapour formation in a fuel line caused by heat. The effect is similar to an air lock and acts to prevent fuel delivery. To clear the vapour lock the fuel line must be bled or allowed to cool. | |
VAPSVariable assist power steering | |
Variable Choke CarburettorA carburettor with a variable diameter venturi (choke tube). The variable diameter is obtained by inlet manifold vacuum being applied to one side of a diaphragm or piston and atmospheric pressure to the other side. This arrangement produces a constant depression and relatively accurate fuel metering. | |
Variable ResistorA resistor that can have its value changed manually. | |
Variable VenturiA venturi (narrowing of a tube) that can be changed. Usually refers to a carburettor. See also Variable Venturi Carburettor. | |
Variable Venturi CarburettorSee Variable Choke Carburettor. | |
VarnishA burnt gum deposit from petrol that forms in the inlet tract of carburettors and on piston skirts. | |
VATVane Air Temperature Sensor. | |
VCCViscous Converter Clutch | |
VCMVehicle control module. An electronic control unit that controls a wide range (or all) of the vehicle functions. | |
VDCVolts Direct Current | |
Vee BeltDrive belt made with a V section. | |
VehicleAnother name for the binder, into which all of the other ingredients of a paint mixture are added. This includes pigment solvents, diluents, resins, driers, etc. | |
Veiling (cobwebbing)The formation of a web or strings in a paint as it emerges from a spray gun, usually caused by too high viscosity, low atomising air pressure or a combination of both. | |
VelocitySpeed in a designated direction. | |
Vent PipesPipes used to ventilate something such as a fuel tank or crankcase. | |
VentilatedAir circulating freely in room, disc, etc. | |
VenturiConvergent-divergent nozzle which accelerates air flow and lowers static pressure in gases or vapours flowing through it. In a carburettor the venturi provides the depression in the air flow pressure causing the fuel to be drawn from its float chamber into the air stream. | |
VerbalAny form of communication that uses words, i.e. speaking and writing in the form of letters, newspapers, emails etc. | |
VibrationHigh frequency oscillating wave producing sound or pulsating feeling. | |
Vibration DamperA device, usually fitted to a rotating shaft (crankshaft) that dampens the vibrations produced in the shaft by rotary imbalance or a pulsed drive. | |
VINVehicle Identification Number | |
VIN (Vehicle Identification Number)Unique code assigned to each vehicle by its manufacturer to identify the model, year, production sequence and other vehicle specific information. | |
VinylA class of monomers which can be combined to form vinyl polymers. Widely used to make chemically resistant finishes, tough plastic trim and other vehicle components. | |
Viscomatic LockA drive mechanism that uses fluid to create a lock at a certain speed. | |
ViscometerA viscometer (also called viscosimeter) is an instrument used to measure the viscosity of a fluid. | |
ViscosityThe flow rate of a liquid. The addition of solvents and/or diluents will reduce the viscosity or fluidity of the paint. Paint viscosity must be carefully adjusted and controlled to allow proper atomisation and flow-out. | |
Viscosity cupA precision device used to measure the viscosity of a liquid by timing how long it takes the liquid to drain out of the cup in a continuous stream. The standard Viscosity cup in use in the UK paint industry is known as a BS B4 or DIN 4 cup, which has a 4mm orifice for the paint to flow through. | |
Viscosity IndexA measure of the change in the flow rate (viscosity) of a liquid with temperature rise. The higher the viscosity index the smaller is the change in viscosity. | |
Viscous CouplingA drive coupling that uses a fluid to transmit drive. Also sometimes a fluid coupling. | |
VOC ContentThe measure of volatile organic compounds (VOC's) in solvent-borne paints. Usually measured as the weight in kilos of non-exempt solvent per tonne of paint. | |
VolatileReadily changes to vapour or gas at ambient temperatures. | |
VolatilityThe tendency of a liquid to evaporate. Liquids with high boiling points have low volatility and vice-versa. Volatility affects flash-off time and fire hazard consideration. | |
VoltageElectromotive force expressed in volts. Potential difference. | |
Voltage DropThe voltage that is lost when an electrical current passes through a resistance. | |
Voltage RegulatorAn electrical or electronic device to maintain a generator output within a narrow voltage range. | |
Voltage StabiliserA mechanical (bimetal) or electronic device used to maintain voltage at a set level. In instrument systems this prevents readings changing as system voltage changes. | |
Voltage StabilizerA mechanical (bimetal) or electronic device used to maintain voltage at a set level. In instrument systems this prevents readings changing as system voltage changes. | |
VoltmeterInstrument for measuring electric potential. Can usually be set to read AC or DC on different ranges. | |
VoltsUnit of electromotive force. Potential difference. | |
VolumeThe capacity of a space as a numerical calculation. | |
Volume SolidsThe percentage, on a volume basis, of the non-volatile material in a paint. | |
Volumetric EfficiencyThe ratio of the actual amount (mass) of air entering an engine cylinder against the actual swept volume of the cylinder. | |
Volumetric SensingA system used by alarms to sense movement inside the vehicle. | |
VOSAThe Vehicle and Operator Service Agency | |
VRVoltage Regulator | |
VSVehicle Sensor | |
VSIVehicle Specific Information, provided to NTs to aid the correct assessment of a vehicle under test. | |
VSSVehicle Speed Sensor. | |
VT20An MOT Test Certificate which includes the English/Welsh dual language version (VT20W). | |
VT20 ETAn MOT Test Certificate for issue during a period of Emergency Testing. | |
VT30A notice of refusal of a MOT Test Certificate including the Welsh counterpart (VT30W). | |
VT32An Advisory Notice – issued to advise of items of concern identified during the test that do not justify the refusal of a test certificate. | |
VT40MOT Inspection Check List used by a NT during a test for vehicles other than motor bicycles (see VT40M). | |
VT40MMotor bicycle MOT Inspection Check List used by a NT during a test. | |
VTSVehicle Test Station | |
VTS DeviceThe Computer device installed at each VTS on which each test must be registered, from which MOT documentation is produced and to perform certain administrative functions. | |
VulcanisationThe treatment of rubber and rubber compounds to make them capable of being moulded. Also used to refer to the sealing of a tyre or tube repair with an adhesive and heat process. | |
VVCVariable Valve Control | |
VVTVariable Valve Timing | |
W |
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WanderThe tendency of a vehicle to drift away from the steered course when being driven. Usually associated with low or uneven tyre pressures or tight steering joints. | |
Wankel EngineRotary engine using a three-cornered rotor in a trochoidal chamber. Invented by Felix Wankel. | |
WarpageTwisting or bending distortion. | |
WarrantyThe legal rights given by manufacturers to cover possible defects occurring during a specified time or mileage. | |
Wash PrimerA primer that forms an anti-corrosive chemical film when applied on a bare metal surface. More commonly known as etching or self-etch primer. | |
WasherFlat circular plate with a hole in it. Used to spread the load of a nut or bolt. | |
Waste GateControl valve in the exhaust gas flow through a turbocharger. | |
Water JacketPart of the cylinder block and head of an engine that encloses the cavity through which cooling water flows. | |
Water Pump(1) Pump that circulates the water of an engine's cooling system. Also circulating pump. (2) Any pump for delivering water under pressure, as for screen washing, etc. | |
Water SpottingA condition caused by water droplets evaporating on a finish before it has thoroughly dried or cured, which results in a dulling of the gloss in localised spots. | |
Water TrapA bowl used to separate water from fuel. | |
WaterborneA type of paint which uses water as its primary carrier rather than typical organic solvents. | |
WattUnit of power. Volts X amps. | |
WattageThe power rating of an electrical device. | |
Wave WoundA winding that is wound in waves instead of individual coils. | |
WaveformPattern displayed on an oscilloscope screen. | |
WavelengthThe distance between corresponding points of two consecutive waves. | |
WaxA uniquely formulated blend that protects and produces a durable, high-gloss finish on a painted surface. The application of waxes make it easier to clean painted surfaces. Some also serve as polishes due to containing a percentage of very fine abrasive and are capable of removing minor paint imperfections. | |
Wax InjectionAnti-corrosion body wax injected into box sections. | |
Wax Pellet ActuatorA switch or valve that operates as temperature affects a wax pellet. | |
Wax PluggingFormation of wax in diesel fuel at low temperatures that plugs the diesel fuel line or filter element preventing fuel flow. | |
WaxingSeparation of wax in diesel fuel at low temperatures. | |
WaxstatA thermostat operated by wax. As wax changes state from solid to liquid, its volume changes. | |
WeatheringThe change in a paint film due to exposure to natural forces, such as sunlight, rain, dust and wind. | |
WeatherometerA device used by paint manufacturers to simulate the effects of weathering. Painted samples are subjected to simulated conditions of sunlight, rain, wind and even salt spray, to test their weathering durability | |
Web BrowserA software package that allows you to view pages from the World Wide Web. Examples are Internet Explorer and Netscape. | |
Web PageA document, usually written in HTML (Hypertext Markup Language), that can be accessed on the Internet. | |
Web SiteA collection of electronic 'pages'. | |
WebbingDescription of the material used for seat belt straps. | |
WedgesA method of increasing force by use of a taper or inclined plane. | |
Weight SolidsThe percentage on a weight basis, of non-volatile (i.e. the ingredients that will not evaporate) material in a paint. | |
Weight TransferThe shift of a vehicle's weight towards the front when braking and towards the rear during rapid acceleration. | |
Welch PlugA dished steel disc used as a core plug in engines and cylinder heads. | |
Wet ClutchA friction clutch that runs in an oil bath. | |
Wet Film GaugeA device used to determine wet film thickness of paint immediately after application. This is obviously a type of destructive test, as the paint surface is damaged by the gauge. | |
Wet LinerNot strictly a liner as it does not line a cylinder, but is the cylinder of a water cooled engine that fits into the cylinder block in contact with the coolant. | |
Wet SandingA technique involving the sanding of a surface while it is being flushed with water. This aids with the smoothing out of surface defects before subsequent coats are applied. | |
Wet SpotsDiscolouration caused where the paint fails to dry and adhere uniformly. | |
Wet Sump (Oil Pan)An engine lubrication system where the reservoir of lubricating oil is held in a sump below the engine. As distinct from a dry sump where the reservoir of lubricating oil is kept in a separate tank. | |
Wet-on-Wet ApplicationA painting method by which a second coat of paint is applied over the first before it hardens and dries. Special primers have been developed which allow for colour to be applied on top of them with little or no flash-off time | |
WettingThe process by which a liquid forms intimate contact with the substrate to which it is applied. | |
Wheel AlignmentThe relative angle of the road wheels to the true longitudinal axis of the vehicle. The toe angle is the degree of variation needed to bring the wheels into true rolling motion when the vehicle is travelling. Also known as 'toe'. | |
Wheel BaseThe dimension from the centre of the front axle to the centre of the rear axle(s). | |
Wheel BearingRoller or ball bearing used to support a drive shaft or a wheel on a stub axle. | |
Wheel CylinderA brake hydraulic cylinder in a drum brake. It is fitted to the back plate on the wheel axle assembly. | |
Wheel HubThe centre assembly of a wheel containing the wheel bearings. | |
Wheel NaveConnects the rim to the wheel hub. | |
Wheel OffsetThe distance from the wheel nave to the centre line of the wheel. Used to accommodate the brake assembly and bring the centre line of the wheel into close alignment with the centre line of the steering swivel and wheel hub. | |
Wheel PlaneThe plane (flat area) through the wheel at right angles to the axle. | |
Wheel RimPart of wheel that holds the tyre. | |
Wheel Slip (spin)Loss of friction between a tyre and the road surface allowing the wheel to spin faster than the speed of the vehicle. | |
Wheel TrackThe dimension between the centres of the road wheels on one axle. Also known as tread. | |
Wheelslip (Spin)Loss of friction between a tyre and the road surface allowing the wheel to spin faster than the speed of the vehicle. | |
Whip (Whirl)The throw out of a rotating shaft. In relation to drive shafts whip can create unpleasant harmonics and vibrations. | |
WhitemetalTin based alloy used as a coating for plain steel bearings. | |
WhitworthStandard size of thread. Old British standard. | |
WindingCoil of wire used to create magnetism. | |
WindingsCoils of wire used to create magnetism when a current flows through them. | |
Wiring Harness (Loom)The bundle of cables that are bound together to form the electrical distribution system for a vehicle or system. | |
Woodruff KeyA locating device that sits in slots on a shaft and pulley or gear wheel. Also known as a half-round key or in some cases just key! | |
Word ProcessorA computer program used to create text based documents such as letters and memos, although graphics may also be added. | |
WorkPerformed when energy is used. The SI unit is the 'Joule'. | |
World Wide WebThe www is a collection of electronic 'pages' that can be accessed over the Internet. The World Wide Web is NOT the same as the Internet, it is only a part of it. | |
Worm GearGear set with a screw pinion driving a wheel with meshing circumferential teeth. | |
WOTWide open throttle | |
Woven abrasive padA fibre pad used to lightly sand a surface. These pads, which are supplied in various grades, last much longer than abrasive papers and are less likely to rub through on sharp angles and panel edges. | |
Wrap-aroundThe phenomenon by which electrically charged paint droplets curve around to the rear side of the object being painted. Used to great advantage in Electrostatic spraying of components with complicated shapes | |
WrinklingSurface distortion that occurs in a thick coat of enamel due to uneven cure or recoating of an uncured paint film. | |
X |
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X-by-wireDrive-by-wire, DbW, by-wire, or x-by-wire technology in the automotive industry replaces the traditional mechanical and hydraulic control systems with electronic control systems using electromechanical actuators and human-machine interfaces such as pedal and steering feel devices. | |
X-rayA word to make sure that there is always a word in the X section! | |
XenonAn inert gas used in some discharge type light bulbs. | |
XyleneA high solvency, medium evaporating, aromatic hydrocarbon solvent. | |
Y |
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YY not... | |
Y-type StatorAn alternator stator winding with the three-phase coils connected at the centre in order to give a large voltage output. The normal winding for light vehicle applications. Also star wound stator. | |
YawMovement or oscillation about the vertical axis of a vehicle when travelling. | |
YokeA forked end on a component. Originates from the two arms used to attach a cart to a horse. | |
Z |
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ZebraA word to make sure that there is always a word in the Z section! | |
Zener DiodeA semiconductor device that conducts an electrical current when its operating voltage is reached. | |
ZincA brittle bluish-white metal used in alloys and battery cell plates and electrodes. | |
Zinc ChromateA yellow, corrosion resistant pigment useful on steel. | |
Zinc OxideWhite pigment, useful to prevent mould or mildew on paint films. | |