Necessity of ignition
Controlled ignition for premix engines: need and principle

This section briefly describes the components and operation of a spark-ignition engine based on a 4-stroke cycle (the most common cycle used today).

The four strokes (intake, compression, expansion and exhaust) of an engine are described in figure 1 .

In the case of a 4-stroke engine, motion is imparted by the crankshaft during the intake, compression and exhaust phases, and the piston becomes the engine during the expansion phase (transmission of the energy released by combustion in the form of mechanical energy to the crankshaft).

The diagram at