AskDefine | Define throttle

Dictionary Definition



1 a valve that regulates the supply of fuel to the engine [syn: accelerator, throttle valve]
2 a pedal that controls the throttle valve; "he stepped on the gas" [syn: accelerator, accelerator pedal, gas pedal, gas, gun]


1 place limits on (extent or access); "restrict the use of this parking lot"; "limit the time you can spend with your friends" [syn: restrict, restrain, trammel, limit, bound, confine]
2 kill by squeezing the throat of so as to cut off the air; "he tried to strangle his opponent"; "A man in Boston has been strangling several dozen prostitutes" [syn: strangle, strangulate]
3 reduce the air supply; "choke a carburetor" [syn: choke]

User Contributed Dictionary






  1. A valve that regulates the supply of fuel-air mixture to an internal combustion engine and thus controls its speed; a similar valve that controls the air supply to an engine.
  2. The lever or pedal that controls this valve.


a valve
the lever or pedal that controls this valve


  1. To cut back on the speed of an engine, a person or organization.
  2. To strangle or choke someone.


to cut back speed
Swedish: gasa, öka gasen  (= increase the speed/throttle up) strypa gasen, minska gasen  (= decrease the speed)undertrycka (of a person)begränsa (of an organization)
to strangle someone
Translations to be checked
  • ttbc Spanish: acelerador, estrangulador

Extensive Definition

A throttle is the mechanism by which the flow of a fluid is managed by constriction or obstruction. An engine's power can be increased or decreased by the restriction of inlet gases (i.e., by the use of a throttle). The term throttle has come to refer, informally and incorrectly, to any mechanism by which the power or speed of an engine is regulated.

Internal combustion engines

In a petrol internal combustion engine, the throttle is a valve that directly regulates the amount of air entering the engine, indirectly controlling the fuel 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 or accelerator.
The throttle is typically a butterfly valve. In a fuel-injected engine, the throttle valve is housed in the throttle body. In a carbureted engine, it is found in the carburetor.
When a throttle is wide open, the intake manifold is usually at ambient atmospheric pressure. When the throttle is partially closed, a manifold vacuum develops as the intake drops below ambient pressure.
Usually the throttle valve is mechanically linked with the throttle pedal or lever. In vehicles with electronic throttle control, the throttle valve is electronically controlled, which allows the ECU greater possibilities in reducing air emissions.
Because Diesel engines use compression ignition, they do not need to control air volumes or mixture (indeed this would be undesirable). Thus they lack a butterfly valve in the intake tract, and do not have a throttle. They instead regulate engine power by directly controlling the quantity of fuel injected into the cylinder at top dead centre (TDC) of the compression stroke.

Environmental aspects

Regulation of the throttle is also a mechanism for controlling engine exhaust emissions. In many modern internal combustion engines an electronic throttle is used, eliminating the older accelerator cable.
Throttle application via the accelerator pedal also results in increased sound emission from the engine. At lower operating speeds this component of vehicle noise is prominent, contrasted with higher operating speeds, for which aerodynamic and tire noise are more significant.

Other engines

Most engines have some kind of throttle control, though the particular way that power is regulated is often different.
Liquid rockets are throttled by controlling the pumps which send liquid fuel and oxidizer to the combustion chamber. Solid rockets are more difficult to throttle, but some may have mechanisms for this.
In a jet engine, engine output is also directly controlled by changing the amount of fuel flowing into the combustion chamber, usually with an autothrottle.


throttle in Arabic: دواسة البنزين
throttle in German: Gaspedal
throttle in Dutch: Gaspedaal
throttle in Japanese: スロットル

Synonyms, Antonyms and Related Words

abduct, arrest, asphyxiate, backpedal, backwater, bottle up, brake, burke, carry off, censor, check, choke, choke off, clamp down on, clip the wings, cork, cork up, crack down on, crush, curb, damp down, decelerate, deflate, delay, detain, disarm, draw rein, drown, dumbfound, ease off, ease up, enchain, extinguish, gag, garrote, hamstring, handcuff, hobble, hog-tie, hold back, hold down, hold in check, hold up, hush, hush-hush, impede, jump on, keep back, keep down, keep under, kidnap, kill, knock out, let down, let up, lose ground, lose momentum, lose speed, manacle, moderate, muffle, muzzle, obstruct, paralyze, pour water on, prostrate, put down, put to silence, quash, quell, quench, quiet, quieten, reef, rein in, relax, repress, retard, set back, shanghai, shush, shut down on, silence, sit down on, sit on, slack off, slack up, slacken, slow, slow down, slow up, smash, smother, soft-pedal, squash, squelch, stanch, stay, stifle, still, stop the breath, strangle, strike dumb, stultify, subdue, suffocate, suppress, take in sail, throttle down, truss up
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