What is the formula for piston speed?

The formula for piston speed is derived from the relationship between the stroke length of the piston, its rotation speed in RPM (revolutions per minute), and the geometry of the engine. The correct formula, which is represented as PS = (2 x Stroke x RPM)/12, accurately captures this relationship by incorporating several key components.

The term "Stroke" refers to the distance the piston travels from its top position to its bottom position within the cylinder. When considering RPM, which describes how many times the crankshaft completes a full revolution per minute, it is essential to take into account the movement of the piston during each complete revolution. Since the piston moves up and down twice in each full revolution (once in each direction), the stroke length is doubled, giving rise to the "2 x Stroke" factor in the formula.

The division by 12 converts the speed into feet per minute, presuming the stroke length is input in inches. This conversion is necessary for the appropriate units to match when calculating piston speed.

Understanding the derivation and components of this formula is critical for calculations involving engine mechanics, particularly when determining the speed at which a piston operates within an internal combustion engine. This knowledge can assist in optimizing performance and assessing engine specifications.