Turbo-charging: A method of increasing engine power and decreasing emissions by rerouting hot exhaust gases through a turbine which drives an air compressor which forces more air into the engine cylinders.

Tune-up: A regular maintenance function, usually associated with the replacement and adjustment of components in the electrical and fuel systems of a vehicle for the purpose of achieving optimum performance.

Transverse engine: An engine is which the crankshaft is placed side-to-side relative to the wheels of the vehicle. Also called an east-west engine. Most modern front wheel drive vehicles use this engine orientation.

Transistor: It consists of three alternate sections of N- and P- materials. It may be NPN or PNP type. Its central section is called base which controls the main current through the emitter and the collector. The current through the base is called control current.

Trailing throttle: The driving condition when the vehicle is being driven with accelerator pedal released.

Torque: It is the force of rotation acting along the crankshaft axis at any instant of time. From the engine it goes through the transmission, to the road wheels. It is responsible for rotation of the wheels and hence for the pulling of the vehicle.

Timing chain: A roller chain driven by the crankshaft for operating the camshaft.

Timing belt: A square-toothed, reinforced rubber belt which is driven by the crankshaft and operates the camshaft.

Thyristor: A semiconductor rectifier which can control the output power supplied to an electrical load, with the minimum wastage of energy. The word 'thyristor' has been derived from 'thyratron' and 'resistor', the thyratron being the predecessor of the thyristor.

Throttle body injection: The type of fuel supply system in which the injectors are located on the engine throttle body, thereby supplying fuel to more than one cylinder. It is also known as single point or central injection.

Throttle body: An engine housing containing the throttle butterfly valve for regulating the air flow through the inlet manifold.

Three-way converter: A catalytic converter employed to control the levels of all the three main pollutants in the engine exhaust, viz., unburnt hydrocarbons, carbon monoxide and nitrogen oxides.

Thermosyphon system: A simple engine cooling system based on the natural convection caused by the difference in densities of the hot and the cold regions of the cooling water; is now obsolete.

Thermal Efficiency - Indicated thermal efficiency or brake thermal efficiency: Thermal Efficiency of an engine is the ratio of the work output and the heat input to the engine. Depending upon the type of work, it may be called indicated thermal efficiency or brake thermal efficiency.

Tappets: The components to convert the rotary motion of the camshaft into reciprocating up and down motion of the push rods.