Mean Piston Speed
Mean piston speed is a simple but powerful figure of merit for engine design, calculated as MPS = 2LN / 60, where L is the stroke length (in meters) and N is engine speed in RPM. The factor of 2 accounts for the piston traveling the full stroke twice per revolution (up and down).
Most production engines are designed to keep mean piston speed under roughly 20–25 m/s at maximum RPM, since higher speeds dramatically increase mechanical stress, wear, and the risk of component failure. This is why long-stroke engines typically have lower redlines than short-stroke engines of similar displacement.
Last reviewed August 2026