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