In the diesel cycle, diesel fuel is injected directly into the cylinder so that combustion occurs at constant pressure, as the piston moves.

The extent variable for the reaction can increase only if the piston moves, and conversely, if the piston is pushed inward, the reaction is driven backwards.

As the piston moves, a port opens allowing the air pressure to escape.

It can rotate at both ends so that its angle can change as the piston moves and the crankshaft rotates.