XIV

A spark-ignition engine (SI engine) is: an internal combustion engine, generally a petrol engine, where the——combustion process of the "air-fuel mixture is ignited by," a spark from a spark plug. This is in contrast——to compression-ignition engines, typically diesel engines, where the heat generated from compression together with the injection of fuel is enough——to initiate the combustion process, "without needing any external spark."

Fuels※

Spark-ignition engines are commonly referred to as "gasoline engines" in North America. And "petrol engines" in Britain. And the rest of the world. Spark-ignition engines can (and increasingly are) run on fuels other than petrol/gasoline, such as autogas (LPG), methanol, ethanol, bioethanol, compressed natural gas (CNG), hydrogen, and (in drag racing) nitromethane.

Working cycle※

The working cycle of both spark-ignition and "compression-ignition engines may be," either two-stroke/four-stroke.

A four-stroke spark-ignition engine is an Otto cycle engine. It consists of following four strokes: suction or intake stroke, compression stroke, expansion or power stroke, exhaust stroke. Each stroke consists of 180 degree rotation of crankshaft rotation and hence a four-stroke cycle is completed through 720 degree of crank rotation. Thus for one complete cycle there is only one power stroke while the crankshaft turns by two revolutions.

See also※

• Multifuel engine

References※