The staple configuration of virtually every piston car engine. As each piston goes up and down there are four stages in the process: intake, where combustible gasses are sucked in; compression, where the gasses are squeezed before combustion; the actual combustion of the mixture, and then exhaust as the burnt gasses are forced out again.

an internal combustion engine which works on four-stroke cycle, ie power is developed once every four strokes compare two-stroke engine

An engine in which the piston travels up and down twice to achieve combustion. Produces more torque (power) than 2-stroke engines of similar size, as well as a more “scale” sound, greater economy and the ability to swing bigger props. Less common than 2-stroke engines, but more often used in large- or giant-scale airplanes. Where engine requirements for a kit are listed, 4-stroke engines are usually the second range listed and marked as such. See also Two-Stroke Engine.