Dictionary of Automotive Terms Abbreviations

DICTIONARY OF AUTOMOTIVE TERMS - "Th"

T-handle shifter: A shift lever (usually found on automatic transmissions) mounted on the console and shaped like the letter T

T-handle socket: A tool in which a socket has been welded to a long rod (about 8 to 10 inches). At the other end of the rod, a crossbar has been welded. Thus it is formed in the shape of the letter T. In some instances it speeds up the removal and installation of bolts.

THC: Acronym for Total hydrocarbons

T head: See
T-head engine
Engine type.

T-head

A type of cylinder head in a side valve engine where the valves are either adjacent and parallel or installed on opposite sides of the piston in a configuration resembling a T.
A type of screw or bolt head shaped like a T.

Also See
T-head engine
Engine type
and Crossflow head

T head engine: See
T-head engine.

T-head engine: An engine in which the arrangement of the valves on either side of the Combustion chamber creates a T configuration. Usually the Intake valves are on one side and the Exhaust on the other. The modern crossflow Cylinder heads are variations on this old concept. But the original design is not in Current use.

Theft: See
Car theft

Theft protection: See
Anti-theft security system

Theft system: See
Anti-theft system

Therm: Quantity of heat equal to 100,000 Btu.

Thermac: GM's thermostatically controlled air cleaner system

Thermactor: An air injector type of exhaust emission control system used on Ford vehicles. See Thermal reactor

Thermactor II: Also called Ford's Pulse air system

Thermactor air bypass solenoid: (TAB) an electrical solenoid that switch engine manifold vacuum to bypass the atmosphere

Thermactor air control valve: Combines a bypass (dump) valve with a diverter (up/down stream) valve; controls the flow of the thermactor air in respond to vacuum signals to its diaphragms

Thermactor air control solenoid vacuum valve assembly: Used on thermactor air control systems; consists of two normally open solenoid valves with vents

Thermactor air diverter solenoid: (TAD) and electrical solenoid that switches engine manifold vacuum; when energized, switches Thermactor air from downstream (past the oxygen sensor) to upstream (before the oxygen sensor)

Thermactor exhaust control system: (TEC) an air injector type of exhaust emission control system used by Ford

Therma Fleece: A type of very soft fabric used in a garment to provide insulation, and wicking for cold weather riding.

Thermal: Of, pertaining to, or caused by heat or temp.
Also See
British Thermal Unit
Thermal efficiency
and Thermal reactor

Thermal conduction: Heat transfer within a substance or to another substance by direct contact

Thermal convection: Heat transfer by the combined mechanisms of fluid mixing and thermal conduction

Thermal cracking: A refining process in which heat and pressure are used to break down, rearrange, or combine hydrocarbon molecules. Thermal-cracking includes gas oil, visbreaking, fluid coking, delayed coking, and other thermal cracking processes (e.g., flexicoking).

Thermal deterioration: Loss of strength of carcass cords due to heat generated in a tire.

Thermal efficiency

The percentage of the heat developed in the burning fuel charge that is actually used to develop power determines thermal efficiency. When fuel is combusted in an engine not all the fuel is converted into power. Some is lost in overcoming Friction and some escapes down the Tail pipe in the hot Exhaust gases so this percentage is always less than 100%. Efficiency will vary according to engine design, use, etc. If an engine uses a great deal of the heat to produce power, its thermal efficiency would be high.
A measure of the efficiency of converting a fuel to energy and useful work; useful work and energy output divided by higher heating value of input fuel times 100 (to show percent).
Efficiency with which a power source transforms the potential heat of its fuel into work or output, expressed as the ratio of the useful work done by the power source in a given time interval to the total heat energy contained in the fuel burned during the same time interval, both work and heat being expressed in the same units.

Also See
Adiabatic engine.

Thermal equilibrium: The point at which the rate of cooling becomes equal to the rate of heat generation in a tire. Also called heat balance.

Thermal head: The initial temperature of exhaust gas upstream of a catalytic converter

Thermal ignition control: (TIC) device used by Chrysler that shifts the vacuum advance vacuum source from ported vacuum to manifold vacuum when coolant temperature exceeds 107°C

Thermal inertia: The reciprocal of Thermal response

Thermal insulation: Material which is a poor conductor of heat; used to retard or slow down flow of heat through wall or partition.

Thermal limiter: Fuse-like device that protects the low refrigerant protection system circuit on GM vehicles. Stops compressor operation when low pressure is sensed
Also See
Low refrigerant protection system.

Thermally-actuated element: That part of a control device which is directly acted upon by temperature changes and originates or supplies motion or energy directly or indirectly to operate a control device (valve, switch, etc.).

Thermal management: The directing of heat entering or exiting a system.

Thermal protector: A protective device, built into the electric motor, that disconnects the motor from its power source if the temperature becomes excessive for any reason

Thermal radiation: Heat transfer from one substance to another by means of electromagnetic waves

Thermal reactor

(TR)

A high-volume thermally isolated chamber replacing the Exhaust manifold and providing a place for high-temperature afterburning of exhaust pollutants. Found on all Mazda rotary engines and some Piston engines (BMW for example) as well.
A device installed in the exhaust manifold of some air injection systems to promote HC and CO oxidation by providing long exhaust gas residence times in a localized area.
An emission control device that accepts raw exhaust gases from the engine and subjects them to extremely hi temperature to oxidize noxious emissions. Uses a specially designed exhaust manifold that uses heat and air to burn the unburned hydrocarbons in the exhaust gases to reduce pollution

Thermal relay: A relay actuated by the heating effect of the current flowing through it; A Heat-operated electrical control used to open or close a refrigeration system electrical circuit. This system uses a resistance wire to convent electrical energy into heat energy.

Thermal resistance: (R-Value) This designates the resistance of a material to heat conduction. The greater the R-value the larger the number.

Thermal response: The rate of temperature rise in a reactor if no heat is withdrawn by cooling. Its reciprocal is thermal inertia

Thermal storage: Storage of heat or heat sinks (coldness) for later heating or cooling. Examples are the storage of solar energy for night heating; the storage of summer heat for winter use; the storage of winter ice for space cooling in the summer; and the storage of electrically-generated heat or coolness when electricity is less expensive, to be released in order to avoid using electricity when the rates are higher. There are four basic types of thermal storage systems: ice storage; water storage; storage in rock, soil or other types of solid thermal mass; and storage in other materials, such as glycol (antifreeze).

Thermal switch: A bimetal switch that controls glow plug operation

Thermal time valve: A valve which senses temperature, typically the temperature under the hood, and gives full vacuum advance when the temperature is below 5.5°C above this temperature, the thermal time valve allows the distributor vacuum to be controlled by the thermal vacuum switch; includes a delay of typically 20 seconds to allow full spark advance for better hot starting

Thermal unit: See
British thermal unit

Thermal vacuum switch

(TVS)

Measures either air/fuel temperature, underhood temperature, or coolant temperature, or a combination of any two to regulate the EGR valve accordingly.
A temperature sensitive switch that shifts the source of the advance from ported to manifold vacuum when coolant temperature reaches approx 225 deg F
A vacuum switch that controls vacuum levels or routing based on coolant or ambient air temperature.

Thermal vacuum valve: (TVV) A valve with the same function as a thermal vacuum switch. TVS units, which serve to interrupt exhaust gas recirculation when the temperature is too low, are located in the vacuum line between the ECR valve and inlet manifold or carburetor

Thermal Value: Calories per gram of BTU per pound produced by burning fuels.

Thermal vent valve: (TVV) a temp-sensitive valve assembly located in the canister vent line. The TVV closes when the engine is cold and opens when it is hot to prevent fuel tank vapors from being vented through the carburetor fuel bowl when the fuel tank heats up before the engine compartment

Thermistor

Resistor that changes its resistance inversely with temperature
A temp-sensitive, heat-activated resistor. Use in air conditioning system sensors.
Basically a semiconductor which has electrical resistance that varies with temperature.

Thermocouple

An electrical temperature sensor. As opposed to a resistance thermometer, the thermocouple operates without an external voltage; it consists basically of two conductors of dissimilar metals, typically copper/constantan, iron/constantan, nickel-chromium/nickel, which are connected at their ends; one joint, the hot junction, is exposed to the temperature to be measured, the other joint, the cold or reference junction, is held at a fixed, known temperature; a thermoelectrical voltage is developed between the two junctions which is proportional to the temperature difference between the junctions
Device which generates electricity, using principle that if two unlike metals are welded together and junction is heated, a voltage will develop across the open ends.
A junction of two dissimilar materials which generates a minute voltage in proportion to its temperature. Such devices may be used as a signal source in indicating instruments and control equipment

Thermocouple spark plug: A spark plug with a thermocouple in the center electrode, used to measure the temperatures in the individual cylinders as a function of engine speed and load in order to select the correct heat range

Thermocouple thermometer: Electrical instrument using thermocouple as source of electrical flow, connected to milliammeter calibrated in temperature degrees.

Thermodisk defrost control: Electrical switch with bimetal disk controlled by temperature changes.

Thermodynamics

Part of science which deals with the relationships between heat and mechanical action.
A study of the transformation of energy from one form to another, and its practical application.

Thermoelectric refrigeration: Refrigerator mechanism that depends on Peltier effect. Direct current flowing through electrical junction between unlike metals provides heating or cooling effect depending on direction of current flow.

Thermoforming: The shaping of a polymer sheet while heating

Thermometer: Device for measuring temperatures.; See
Resistance thermometer

Thermomodule: Number of thermocouples used in parallel to achieve low temperatures.

Thermopile: Number of thermocouples used in series to create a higher voltage.

Thermophotovoltaic cell: A device where sunlight concentrated onto a absorber heats it to a high temperature, and the thermal radiation emitted by the absorber is used as the energy source for a photovoltaic cell that is designed to maximize conversion efficiency at the wavelength of the thermal radiation.

Thermoplastic: A plastic material with long chain-like molecules that can repeatedly be softened by heating and hardened by cooling; most plastic parts used on vehicles are made of thermoplastics

Thermoplastic elastomers: Materials which are rubbery at room temperature but which on heating melt to viscous liquids that can be molded and otherwise processed; the change is reversible; on cooling, the melted material reverts to a solid material having rubbery properties

Thermos bottle: Trucker slang for Tanker truck as in "We just bought fifteen new thermos bottle's."

Thermosetting: A polymer which sets at the same time as it is being molded

Thermosiphon system: A solar collector system for water heating in which circulation of the collection fluid through the storage loop is provided solely by the temperature and density difference between the hot and cold fluids.

Thermostat

A temperature sensitive device used in the Cooling system of an engine to control the flow of Coolant between the Cylinder block and Radiator. It is set into the engine block and shuts off the circulation of water until the temperature of the water reaches the point at which the thermostat is set to open. Because automotive Internal combustion engines operate more efficiently when their temperature is maintained within narrow limits, the thermostat closes off the flow of Coolant from the engine to the radiator until the engine has reached the desired operating temperature. Other thermostats are used in the electrical circuit of the vehicle heating system to control the amount of heat supplied to the passengers, in the Manifold heat control system that preheats the Air-fuel mixture going to the Cylinders and in the Automatic choke.
Device which senses ambient temperature conditions and, in turn, acts to control a circuit.

Also See
Aneroid-type thermostat
Wax-type thermostat

Thermostatic air cleaner: (TAC) An air cleaner which also controls the temperature of the air entering the engine. A temperature control is necessary to optimize the air/fuel ratio with regard to minimum exhaust emissions; typically, the TAC regulates air intake temperature at about 27-46°C by means of a control damper that mixes pre-heated air from an inlet at the exhaust manifold with air from a cold air inlet; designs for actuating the damper range from simple thermostatic action to vacuum-motor and stepper-motor control

Thermostatic coil choke: A sensing device mounted on the Carburetor that automatically controls the Choke Butterfly valve by sensing the heat of the Exhaust manifold. Also see Choke.

Thermostatic control: Device which operates system or part of system based on' temperature change.

Thermostatic expansion valve

Metering device that removes pressure from liquid refrigerant, permitting it to expand and vaporize in evaporator
Control valve operated by temperature and pressure within evaporator. It controls flow of refrigerant. Control bulb is attached to outlet of evaporator.
A component which regulates the rate of refrigerant flow into the evaporator as determined by the outlet pipe temperature sensed by the remote bulb.

Also See
Expansion valve

Thermostatic interruptor: A bimetallic circuit breaker in a lighting circuits which switches to an alternative circuit in the event of a fault or short circuit

Thermostatic motor control: Device used to control cycling of unit through use of control bulb. Bulb reacts to temperature changes.

Thermostatic spring choke: A sensing device that automatically controls the Choke Butterfly valve by sensing the heat of the Exhaust manifold. Also see Choke.

Thermostatic switch: A temperature sensitive switch that prevents icing by cycling compressor operation to control system temperature. Bellows and bimetallic switches are typical examples.

Thermostatic vacuum switch: A temperature sensitive switch which allows spark advance when engine idles for long periods

Thermostatic valve: Valve controlled by temperature change response elements.

Thermostatic water valve: Valve used to control flow of water through system, actuated (made to work) by temperature difference. Used in units such as water-cooled compressor and/or condenser.

Thermo-switch: See
Oxygen sensor system thermo-switch

Thermo-syphon: A method of cooling an engine using difference in specific gravity and cold water. No pump is used, but the coolant passages are larger than in a pump-type system

Thermosyphon cooling: A natural cooling, using the fact that two columns of liquid at different temperatures possess natural circulation because the hotter column weighs less on account of its lower density; thus the hot engine must be located at a lower level than the cool radiator

Thermo-time switch: A switch in a continuous injection system that interrupts current from the starter solenoid to the cold-start valve solenoid when the engine is hot or after the starter has been operated for more than a few seconds, in order to prevent flooding

Thermovalve: A valve which opens and closes as a function of temperature

Thermowell

A space which accommodates a temperature sensor.
The temperature sensing point or sensor rather than to the well itself

Thick film integrated: (TFI) Ford electronic ignition system

Thickness: See
Layer thickness

Thief: See
Car thief

Thin: To add thinners to paint in order to adjust the viscosity

Thin needle-nose pliers: A needle-nose pliers with an extra long reach jaws without a wire cutter

Thinner: The Solvent used to thin Lacquers and acrylic products to the proper consistency for application and differs from a reducer which are used for synthetic enamel products. Thinners and reducers are not normally interchangeable, i.e., the corresponding type of thinner/reducer must be used for each type of paint; however, some general-purpose thinners are available. Also see General purpose lacquer thinner

Thinning out: The tendency of liquid paint to form much thicker coatings near the edge of a steel sheet, thereby causing the paint film thickness on the side opposite this edge to decrease

Thin-wall casting: A weight-saving measure on oil filter housings

Third: An intermediate gear used for increasing speed, climbing hills and sometimes for passing; but on a three speed transmission, it is the top gear.

Third brush: A Generator in which a third, movable Brush is used to control Current output.

Third gear: An intermediate gear used for increasing speed, climbing hills and sometimes for passing; but on a three speed transmission, it is the top gear.

Third hand: A tool used on Bicycles to squeeze the brakes together against the rim so that adjustments can be made to the cable.

Third motion shaft: See
Gearbox output shaft

Third port induction: A design feature of a two-stroke engine that relies on the piston position to control induction of the fresh charge. A feature of this design is the use of the third port, i.e., the transfer port, to complement the intake and exhaust ports, e.g., as opposed to two-stroke diesels that have valve-controlled intakes and do not need transfer ports

Third scavenging port: An additional transfer port located opposite the exhaust port of a two-stroke engine cylinder and connecting through the piston skirt to the region above the gudgeon pin and below the piston crown

Thixotropic: Having the property of certain resins and paints that prevents them from running off vertical surfaces

THM: Acronym for Turbo Hydra-Matic

Thompson rotovalve: A type of valve which rotates as it opens and closes.

Thou: An abbreviation for thousandth or one divided by a thousand; a small measurement representing 1/1000th of an inch as in Ten thou (0.01) is equal to 0.25 mm."

Thrash: A colloquial term for pushing an engine to its limits

Thread

The spiral grooves on a screw, bolt, or nut.
Helical groove in a cylindrical hole, nut, etc., formed a tap or lathe tool (female or internal thread).

Also See
Right-hand thread
Left-hand thread
B thread
Buttressed thread
Class A thread
Class B thread
Coarse thread
Cut thread
Depth of thread
External thread
Female thread
Incomplete thread
Internal thread
Left-hand thread
Left hand thread
Male thread
Mating thread
Metric thread
National coarse thread
National fine thread
Nominal thread diameter
Nut thread
Right-hand thread
Right hand thread
Rolled thread
Unc thread
Unf thread
V-thread

Thread angle: The angle between the adjacent flanks of a thread

Thread crest: The highest point of a screw thread, opposite the root

Thread-cutting screw: A British term for a Self-tapping screw. A self-drilling fastener that drills its own hole, taps a mating thread, and then fastens, all in a single operation

Thread diameter: The diameter measured from the crest of a thread to the corresponding crest on the opposite side of the bolt or screw. Also see Nominal thread diameter

Threaded: See
Cross-threaded

Threaded headset: A headset at the top of the steerer tube with threads cut into it to accommodate a threaded fork. This system is found on road bicycles while threadless headsets are used on mountain bikes. A threaded headset must be used with a threaded fork. Threaded forks are most commonly found on road bikes. The threaded portion of the fork is located at the top of the steerer tube. For forks with threaded steerer tube The adjustable race screws on to the steerer, and a locknut screws on after the adjustable race to secure it. There is normally a keyed washer between the adjustable race and the locknut for extra security.

Threaded insert: A threaded coil that's used to restore an original thread size hole that has damaged threads; the hole is drilled oversize and tapped, and the insert is threaded into the tapped hole

Threaded rod: A shaft (usually fairly long) with threads from one end to the other. It is usually cut to the length required.

Threaded stem: A bicycle handlebar stem with threads which is inserted into the fork steerer tube. Also called quill type.

Thread file: A tool for restoring internal or external threads by filing

Thread gauge: See
Screw pitch gauge

Thread height: The distance from root to thread crest, measured perpendicular to the axis of the thread

Thread insert: A screw-thread system that allows the use of high-strength cap screws and studs in light soft metals, such as aluminum and magnesium, through the use of a phosphor bronze or stainless steel coil which is screwed into a threaded hole; the thread insert can also be used to repair damaged threads

Threadless headsets: A bicycle headset which accommodates forks with an un-threaded steerer tube.

Threadless stem: A bicycle handlebar bar stem that bolts directly to the fork steerer tube. Originally developed for use on mountain bikes but becoming more and more common on road bikes.

Thread pitch: See
Pitch

Thread pitch gauge: See
Screw pitch gauge

Thread root: The lowest point of a screw thread, where the thread joins the body. It is opposite of Crest

Three: See
Big three
Cross three

Three-chamber system: A test installation consisting of a salt spray chamber, a cold chamber, and a climatic chamber

Three-circuit-split brake system: Unique to the Teves anti-lock system. Uses the two hydraulic circuits of a dual master cylinder to individually actuate the front brakes, while the rear brakes are actuated by pressure from the hydraulic brake booster.

Three-cross: A spoking pattern in which a spoke passes over two and under a third spoke before being attached to the rim

Three-door: A subcompact hatchback with two side doors and one liftgate

Three-door hatchback coupe: Three-door hatchback coupe

Originally a small opening in the deck of a sailing ship, the term hatch was later applied to airplane doors and to passenger cars with rear liftgates. Various models appeared in the early 1950s, but weather-tightness was a problem. The concept emerged again in the early 1970s, when fuel economy factors began to signal the trend toward compact cars. Technology had remedied the sealing difficulties. By the 1980s, most manufacturers produced one or more hatchback models, though the question of whether to call them "two-door" or three-door never was resolved. Their main common feature was the lack of a separate trunk. Liftback coupes may have had a different rear-end shape, but the two terms often described essentially the same vehicle.

Three-link suspension: A variation on the Four-link suspension. An upper link is typically removed. This arrangement was used on lower powered cars to reduce cost.

Three-phase: Operating by means of combination of three alternating current circuits which differ in phase by one-third of a cycle.

Three phase electrical: A combination of three circuits energized by alternating electromotive forces that differ in phase by one third of a cycle. See Single phase electrical

Three-phase four wire system: A system of alternating-current supply comprising four conductors, three of which are connected as in three-phase three-wire system, the forth being connected to the neutral point of the supply, which may be grounded.

Three-phase power: Power generated and transmitted from generator to load on three conductors.

Three-phase three wire system: A system of alternating-current supply comprising three conductors between successive pairs of which are maintained alternating differences of potential successively displaced in phase by one-third of a period.

Three-piece alloy wheel: A type of forged alloy wheel with a wheel spider or wheel disc and a divided rim consisting of an outer and an inner rim well; the rim is bolted to the spider or the disc

Three-point seat belt: A combined lap-shoulder belt fastened at three points, usually with an automatic retractor

Three-port engine: The traditional two-stroke engine design incorporating the intake port connecting the crankcase to the atmosphere, the transfer port connecting the crankcase to the combustion chamber, and the exhaust port to evacuate the spent gas from the combustion chamber. The term is used even if the three-port types are used in pairs

Three-quarter cam: A type of camshaft for race car engines which increases lift of valve, speed of valve opening and closing, length of time valve is held open, etc. Also called Full cam Race cam or Semi-race cam depending upon design

Three-quarter floating axle: A rear axle assembly in which the weight of the vehicle is borne by the outer bearings of the axle shafts, mounted between the hubs and axle housing

Three-quarter race camshaft: A description of the Custom Camshaft indicating the type of lobe grinding which, in turn, dictates the type of use. Other grinds are one-quarter race, full-race, street-grind, etc.

3-spd: Abbreviation for Three-speed", either Manual transmission or Automatic transmission.

Three speed: A Transmission which has three forward gears.

Three-speed: A Transmission which has three forward gears.

Three-speed transmission: A Transmission which has three forward gears.

Three-valve engine: An engine with two intake valves and one exhaust valve per cylinder. A four-cylinder three-valve engine is also called a 12-valve engine

Three-way catalyst: (TWC) A catalyst for the simultaneous conversion of the three exhaust pollutants HC, CO, and NO_x

Three way catalytic converter: See
Three-way catalytic converter.

Three-way catalytic converter: A pollution control device which reduces all three noxious substances HC, CO, and NO_x.

3-way catalytic converter: See
Single-bed 3-way catalytic converter

Three-way valve

Multi-orifice (opening flow control valve with three fluid flow openings.
A hydraulic system component incorporating metering, proportioning, and warning light activation.

Three-wheeler

A light car with three wheels; formerly made popular by some British vehicles like the Morgan, the BSA, the Coventry Victor, and the Reliant Robin.
A modified motorcycle which has one wheel in the front for steering and two at the back driven by a Volkswagen engine.

Threshold Limit Value: (TLV) Time-weighted average concentration of an air pollutant at the workplace for a conventional 8-hour workday and a 40-hour workweek, to which nearly all workers may be repeatedly exposed without adverse health effects.

Throat: See
Actual throat
Carburetor throat
Venturi

Throat depth: An indicator of the reach of welding clamps such as C-clamps

Throat of a fillet weld: Distance from the weld root to the weld face.

Throaty: A rough-sounding exhaust noise which is pleasant to some and irritating to others.

Throttle: The device that controls the Vacuum created in the Venturi of the Carburetor. The greater the vacuum, the richer the Fuel-air mixture. The throttle enables the engine to run on a richer mixture and produce more power for high-speed driving. It consists of a Throttle arm located on the outside of the Carburetor and connected to the Gas pedal (or throttle twist grip on a motorcycle), which in turn activates a throttle Butterfly valve at the base of the Carburetor barrel where it joins the Intake manifold.

Also See
Cranking On The Throttle
Depress the throttle pedal
Ease up on the throttle
Engaging the throttle
Full throttle enrichment
Full throttle
Pumping the throttle pedal
Pump the throttle pedal
Wide open throttle

Throttle arm: The lever that actuates the Throttle.

Throttle body: A housing containing a valve to regulate the airflow through the Intake manifold. The throttle-body is usually located between the air cleaner and the intake Plenum.

Throttle body fuel injection: A form of fuel injection in which the injectors are located at the engine's Throttle body thereby feeding fuel to more than one cylinder. Such an arrangement saves money by using fewer injectors; but because it routes both fuel and air through the Intake manifold it eliminates some of the tuning possibilities offered by Port fuel injection. Also called Single point injection

Throttle body injection: See
Throttle body fuel injection

Throttle butterfly: A valve in the throat of the Carburetor which regulates the amount of the flow of Gasoline. See Throttle valve.

Throttle enrichment: See
Full throttle enrichment

Throttle gauge: A tool with straight calibrated measuring pins for determining throttle and choke valve gaps

Throttle kicker: Throttle kicker

A sensor that uses a vacuum diaphragm to push a rod against the throttle linkage to increase idle speed. A solenoid valve controls vacuum supply.

Throttle microswitch: A device that signals the ECU as to how far the throttle flap is closed so that the ECU can determine the spark advance points or the fuel injection cut-out on deceleration.

Throttle pedal: The Gas pedal which operates the Throttle butterfly through a series of Linkages.

Also See
Depress the throttle pedal
Ease up on the throttle pedal
Pumping the throttle pedal
Pump the throttle pedal
Step on the throttle pedal
Take foot off the throttle pedal

Throttle position sensor

Throttle position sensor

(TPS)

A potentiometric fuel injection switch with two contacts for the two end positions of the throttle valve, which sends a signal to the electronic control unit when the throttle valve is closed (idle) or wide open (full load). The sensor wiper position is proportional to throttle position. The computer uses this information to control fuel flow
A sensor which provides information on the position of the throtte actuation system.

Throttle potentiometer: A device that provides the ECU with a variable voltage signal of the throttle flap position so that the ECU can determine the dynamic spark advance required and the full load enrichment

Throttle relaxer: A device that mechanically controls throttle position during traction control system operation.

Throttle return spring: A spring which forces the throttle valve closed when pressure is taken off the accelerator pedal

Throttle shaft: A shaft on which the throttle valve disc pivots in a carburetor barrel or inlet tract

Throttle solenoid: A solenoid which operates mechanically on the throttle lever; when energized, the solenoid stem extends and opens the throttle to establish the preset idle speed. Since the early 1970s, most manufacturers have used a throttle solenoid to prevent run-on or dieseling

Throttle spindle: A shaft on which the throttle valve disc pivots in a carburetor barrel or inlet tract

Throttle stop solenoid: A device that maintains engine at speed over curb idle

Throttle valve

A valve in the Carburetor. It is used to control the amount of Air-fuel mixture that reaches the Cylinders. Usually consists of a flat round Disc mounted on a shaft so that it can be tilted at various angles in the Carburetor throttle valve body. It is connected by suitable Linkage to the Accelerator pedal.
A modulator valve in an automatic transmission which is actuated either by the accelerator pedal, by the vacuum in the engine intake manifold, or by the carburetor throttle; it converts line pressure into an engine-load dependent pressure, which is directed to various valves

Throttle valve switch: See
Throttle position sensor

Throttling

Reducing the power output of an engine by closing the throttle, thus restricting airflow through the carburetor or intake tract.
Expansion of gas through orifice or controlled opening without gas performing any work as it expands.

Also See
Poa suction throttling valve
Sonic throttling

Throttling valve: See
POA suction throttling valve
Suction throttling valve (STV)
Evaporator pressure regulator valve (EPR)
Suction throttling valve

Through: See
Flow through ventilation

Through bolt

Any bolt which is inserted through the parts of an assembly and secured on the other side by a nut.
One of the two long bolts that holds the starter or alternator assembly together

Through ventilation: See
Flow through ventilation

Throw

The offset portion of the Crankshaft designed to accept the Connecting rod. Also see Crankpin.
The distance from the center of the Crankshaft Main bearing to the center of the Connecting rod Journal. The Piston stroke is twice the throw distance.

Also See
Crank throw

Throwing: Elongating certain sections of a panel by hammering. Opposite to Tucking. When making a section rounded along the inner and outer edges that is to be folded along the outer edge, the length of the outer edge must be increased. This is achieved by regular hammering, which causes the edge of the panel to stretch, reducing its thickness by spreading the metal

Throwing a rod: The action of breaking a connecting rod. Often the rod will force its way out of the side of the engine resulting in major damage which is expensive to repair. In most cases the rod breaks because of the lack of enough oil to cool the rod.

Throwout: See
Throw-out bearing
Clutch throwout fork.

Throw-out: See
Throwout bearing
Clutch throwout fork.

Throwout bearing: See
Throw-out bearing.

Throw-out bearing: Throw-out bearing

A part of the Clutch activated by the Clutch pedal that allows the Clutch to disengage. If you allow the vehicle to Idle in gear with the Clutch pedal depressed, instead of shifting to Neutral gear, you can wear out the throwout bearing. The British term is Clutch release bearing".

Also See
Free pedal play
Clutch throw-out bearing

Throw-out fork: See
Clutch throwout fork.

Throwout fork: See
Clutch throwout fork.

Throwout lever: See
Clutch throwout fork

Thrust: To surge powerfully upward or press outward.

Also See
Camber thrust
Piston thrust
Thrust bearing
Thrust washer

Thrust angle: A locational relationship between the front and rear sets of wheels

Thrust bearing: A bearing with Flanges on its two sides that prevents a shaft such as the Crankshaft from moving endwise. In the engine Crankshaft assembly these Flanges are a close fit to the two sides of the Crankpin. If the Crankshaft tends to shift one way or the other the Crankpin sides come up against the flanges preventing excessive endwise movement.

Also See
Clutch release bearing
Clutch thrust bearing

Thrust belt: See
Steel thrust belt

Thrusters: See
Bow thrusters

Thrust load: A load applied in line with an axis of rotation.

Thrust plate: See
Driven plate

Thrust washer

A Bronze or a hardened steel washer placed between two moving parts. The washer prevents longitudinal movement and provides a bearing surface for the thrust surfaces of the parts.
An axially loaded washer, e.g., of a shaft bearing

Thumb nut: A nut or screw with projections enabling it to be turned by thumb and forefinger; a wing nut/screw

Thumbscrew: A nut or screw with projections enabling it to be turned by thumb and forefinger; a wing nut/screw

Thumb shifter: A shifter designed to be operated with the thumbs, such as Shimano Rapid Fire models or Sturmey Archer three-speed models

Thumbwheel: A small wheel for adjusting, which can be turned by using the thumb and forefinger

Thumper: Bikes with large-displacement, single-cylinder, four-stroke engine.

Thunderbird: Click image for books on
Ford Thunderbird

A vehicle brand of which the 1955-57 and 1958-60 models are Milestone cars.

Thyristor: A silicon-controlled rectifier which converts alternating current to a unidirectional current

Thyristor ignition: A Capacitor discharge ignition