Nikolaus August Otto 1832 - 1891

Otto engine: Mode of operation

1. intake stroke: The air-fuel mixture is sucked in the cylinder by the piston sliding downward.

2. compression stroke: The piston sliding now upward compresses the mixture using work of the crankshaft.

3. power stroke: In the upper dead-center, the mixture is ignited. The pressure of the burning mixture pushs the piston back into the cylinder: Work is performed.

4. ejection stroke: The burned exhaust is ejected by the rising piston through a second valve.