In order to increase efficiency, a secondary cylinder is added as an expansion processor to extract more energy from the fuel.
Schmitz's concept engine uses two primary "high pressure" cylinders with standard four-stroke power cycles, in addition to a larger secondary "low pressure" expansion cylinder.
In 1879, Nicolaus Otto built a 5-stroke engine which was commercially produced, but suffered from poor performance.
The prototype has demonstrated an approximately 10% decrease in fuel consumption over a standard gas engine.
[3][4][5][6][7] The operation of a 5-stroke SI engine is as follows:1 – Induction2 – Compression3 – Power4 – Initial exhaust/re-expansion5 – Final exhaust Schmitz's concept was being developed by Ilmor.