Throttle

A throttle is the mechanism by which fluid flow is managed by or .

An engine's power can be increased or decreased by the restriction of inlet gases (i.e., by the use of a throttle), but usually decreased. The term throttle has come to refer, informally and incorrectly, to any mechanism by which the power or speed of an engine is regulated. What is often termed a throttle (in an aviation context) is more correctly called a thrust lever, particularly for jet engine powered aircraft. For a steam engine, the steam valve that sets the engine speed/power is often known as a regulator.

In a petrol/gasoline internal combustion engine, the throttle is a valve that directly adjusts the amount of air entering the engine, indirectly controlling the charge (fuel + air) burned on each cycle due to the fuel-injector or carburetor maintaining a relatively constant fuel/air ratio. In a motor vehicle the control used by the driver to regulate power is sometimes called the throttle pedal, as it controls the throttle opening, although "accelerator pedal" is more accurate, since not all vehicles have throttles. A diesel engine does not have a throttle except there is a throttle valve on the newer diesel engines which is generally referred to as air management valves. Air management valves can be with or without integrated control electronics. Air management valves throttle the intake air in the intake air system of diesel engines via electromotive means in order to achieve precision controlled exhaust gas recirculation and prevent the inconvenient shaking that would otherwise occur when the engine is switched off. The power level of a diesel is controlled by regulating the fuel flow into the engine, thus "throttle" and "gas pedal" are both inaccurate terms when applied to any modern computerized engine, diesel or not. Both types (gas and diesel) are now true throttle- by- wire computerized systems with the main difference being that in gasoline engines, the throttle position ultimately controls the amount of air getting into the engine with the computer supplying the fuel via the fuel injectors; whereas in a diesel the throttle position really only informs the computer to supply the amount of fuel via the injectors and in some newer models the actual diesel fuel pressure.

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