Automotive Glossary
Automotive Glossary
Browse the glossary using this index
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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. | |