Piston Speed Calculator

Created by Krishna Nelaturu
Last updated: Sep 07, 2022
Table of contents:

This piston speed calculator exists to help you determine the mean piston speed of an engine. You've come to the right place if you were looking for average piston speed calculation. In this article, let's briefly look at:

• What is piston speed?
• Average piston speed formula.
• Significance of piston speed.

If you're interested in calculating the piston force, use our piston force calculator.

What is piston speed?

An engine's piston speed is a measure of how fast the piston moves on average in the engine. In a four-stroke engine, the piston starts from the top dead center (TDC) from rest, moves to the bottom dead center (BDC), and back again. This reciprocating motion powers the engine shaft. Since the piston is continuously reciprocating in the engine cylinder, it is hard to pinpoint an instantaneous piston speed. Instead, we use the mean piston speed to understand the degree of stress the engine parts must withstand and design accordingly.

Mean piston speed formula

The formula for mean piston speed is:

$\text{MPS} = 2 \cdot \text{Stroke} \cdot \text{rpm}$

Where:

• $\text{MPS}$ - Mean piston speed or average piston speed;
• $\text{Stroke}$ - Stroke length of the engine cylinder; and
• $\text{rpm}$ - Speed of the engine shaft in revolutions per minute (rpm).

We multiply the scalar factor $2$ here because a piston moves twice the stroke length(from TDC to BDC and BDC to TDC) in one revolution.

For example, a car engine with a stroke length of 82 mm at 6000 rpm would have a mean piston speed of:

\begin{align*} \text{MPS} &= 2 \cdot 82 \text{ mm} \cdot 6000\text{ rpm}\\ &= 984000 \text{ mm/min}\\ &= \frac{984000}{1000 \times 60} \text{ m/s}\\ \text{MPS} &= 16.4 \text{ m/s} \end{align*}

How to calculate engine piston speed with this piston speed calculator

Our piston speed calculator is a testament to the user-friendliness of our tools:

• Enter the stroke length of the engine.
• Provide the engine speed in the revolutions per minute field.
• This piston speed calculator will automatically calculate your mean piston speed.

If you already know the piston speed, you can use it here to determine the engine rpm or stroke length.

Krishna Nelaturu
Stroke
in
Revolutions per minute (RPM)
min⁻¹
Piston speed
ft/min
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