mm
rpm
Result
Mean piston speed24.02 m/s
How it is calculated, with your numbers
- Mean piston speed
mps = 2 × stroke × rpm / 600002 × 49.7 × 14,500 / 60000 = 24.02 m/s
Working uses the metric units the formula is written in.
- stroke Stroke (mm)
- rpm Engine speed (rpm)
- mps Mean piston speed
What it means
In one revolution the piston travels the stroke twice, down and back up. Multiply by revolutions per second and you have the average speed of the piston over a full turn. It is the usual way to compare how hard different engines rev, regardless of their rpm figure: a short-stroke superbike can rev far higher than a long-stroke twin at the same piston speed.
Peak piston speed, at around mid-stroke, is roughly 1.6 times the mean.
Assumptions and limits
- Average over a full revolution. Peak speed and acceleration depend on the connecting rod length as well.
Sources
- Heywood, J. B., Internal Combustion Engine Fundamentals, McGraw-Hill, 1988.