A four-stroke internal combustion engine operates on the Otto cycle, a design conceived by German-born Nicolaus August Otto as early as 1861 and eventually awarded patent number 365701.

Contrast to all modern combustion engines that run the four-stroke Otto cycle that typically features one compression and ignition phase, Porsche’s system adds another. The result is that in ...

That's why the four-stroke system is known as the Otto cycle. Then men called Miller and Atkinson developed variations involving keeping valves open when formerly they were closed, and vice-versa.