Mean piston speed

The mean piston speed is the average speed of the piston in a reciprocating engine. It is obtained by multiplying the stroke length times two for each revolution of the crankshaft by the rotational speed of the engine, since the piston moves up and down the stroke per revolution.

For example, a piston in an automobile engine which has a stroke of 90 mm will have a mean speed at 3000 rpm of

(90 / 1000) * 2 * (3000 / 60) = 9 m/s.

It is a good indicator of the class and performance of an engine relative to its competitors.

Classes

low speed diesels

~8.5 m/s for marine and electric power generation applications

medium speed diesels

~11 m/s for trains or trucks

high speed diesel

~14 m/s for automobile engines

medium speed petrol

~16 m/s for automobile engines

high speed petrol

~20-25 m/s for sport automobile engines or motorcycles

competition

Some extreme examples are Nascar Nextel Cup Series and Formula one engines with ~25 m/s and Top Fuel engines ~30 m/s