Spark-ignition engine

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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.


Spark-ignition engines are commonly referred to as "gasoline engines" in North America, and "petrol engines" in Britain and the rest of the world.[1] 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.[2]

Working cycle[edit]

The working cycle of both spark-ignition and compression-ignition engines may be either two-stroke or 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[edit]


  1. ^ Dabelstein, Werner; Reglitzky, Arno; Schütze, Andrea; Reders, Klaus; Brunner, Andreas (2016). "Automotive Fuels". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. pp. 1–41. doi:10.1002/14356007.a16_719.pub3.
  2. ^ Naijar, Yousef S.H. (2009). "Alternative Fuels for Spark Ignition Engines". The Open Fuels & Energy Science Journal. 2 (2): 1–9. doi:10.2174/1876973X01002010001.