The mean piston speed is the average speed

Speed

In kinematics, the speed of an object is the magnitude of its velocity ; it is thus a scalar quantity. The average speed of an object in an interval of time is the distance traveled by the object divided by the duration of the interval; the instantaneous speed is the limit of the average speed as...

 of the piston

Piston

A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from...

 in a reciprocating engine

Reciprocating engine

A reciprocating engine, also often known as a piston engine, is a heat engine that uses one or more reciprocating pistons to convert pressure into a rotating motion. This article describes the common features of all types...

. It is a function of stroke

Stroke (engines)

Reciprocating motion, used in reciprocating engines and other mechanisms, is back-and-forth motion. Each cycle of reciprocation consists of two opposite motions: there is a motion in one direction, and then a motion back in the opposite direction. Each of these is called a stroke...

 and RPM. There is a factor of 2 in the equation to account for one stroke to occur in 1/2 of a crank revolution (or alternatively: two strokes per one crank revolution) and a '60' to convert seconds from minutes in the RPM term.

MPS = 2 * Stroke * RPM / 60

For example, a piston in an automobile engine which has a stroke of 90 mm will have a mean speed at 3000 rpm of
2 * (90 / 1000) * 3000 / 60 = 9 m/s.

It is a good indicator of the class and performance of an engine relative to its competitors.
Honda S2000

Honda S2000

The Honda S2000 is a roadster that was manufactured by the Japanese automaker Honda Motor Company. It was launched in April 1999 and was created to celebrate the company's 50th anniversary. The car was first shown as a concept at the Tokyo Motor Show in 1995, following which it was launched in...

 has the highest piston speed for any production car (25.2 m/s).

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 Sprint Cup Series and Formula one

Formula One

Formula One, also known as Formula 1 or F1 and referred to officially as the FIA Formula One World Championship, is the highest class of single seater auto racing sanctioned by the Fédération Internationale de l'Automobile . The "formula" designation in the name refers to a set of rules with which...

 engines with ~25 m/s and Top Fuel

Top Fuel

Top Fuel racing is a class of drag racing in which the cars are run on a mix of approximately 90% nitromethane and 10% methanol rather than gasoline or simply methanol. The cars are purpose-built for drag racing, with an exaggerated layout that in some ways resembles open-wheel circuit racing...

engines ~30 m/s