The ''four stroke petrol engine' is based on

A four-stroke engine (also known as four-cycle) is an internal combustion engine in which the piston completes four separate strokes—intake, compression, power, and exhaust—during two separate revolutions of the engine’s crankshaft, and one single thermodynamic cycle. The earliest of these to be developed is the Otto cycle engine developed in 1876 by Nikolaus August Otto in Cologne, Germany, after the operation principle described by Alphonse Beau de Rochas in 1861.