starter

A starter (also self-starter, cranking motor, or starter motor) is an apparatus installed in motor vehicles to rotate the crankshaft of an internal combustion engine so as to initiate the engine's combustion cycle. Starters can be electric, pneumatic, or hydraulic. The starter can also be another internal combustion engine in the case, for instance, of very large engines, or diesel engines in agricultural or excavation applications.
Internal combustion engines are feedback systems, which, once started, rely on the inertia from each cycle to initiate the next cycle. In a four-stroke engine, the third stroke releases energy from the fuel, powering the fourth (exhaust) stroke and also the first two (intake, compression) strokes of the next cycle, as well as powering the engine's external load. To start the first cycle at the beginning of any particular session, the first two strokes must be powered in some other way than from the engine itself. The starter motor is used for this purpose and it is not required once the engine starts running and its feedback loop becomes self-sustaining.

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