# Bore (engine)

(Redirected from Cylinder bore)

In a piston engine, the bore (or cylinder bore) is the diameter of each cylinder.

Engine displacement is calculated based on bore, stroke length and the number of cylinders:[1]

```displacement = π ( .mw-parser-output .sfrac{white-space:nowrap}.mw-parser-output .sfrac.tion,.mw-parser-output .sfrac .tion{display:inline-block;vertical-align:-0.5em;font-size:85%;text-align:center}.mw-parser-output .sfrac .num,.mw-parser-output .sfrac .den{display:block;line-height:1em;margin:0 0.1em}.mw-parser-output .sfrac .den{border-top:1px solid}.mw-parser-output .sr-only{border:0;clip:rect(0,0,0,0);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}1/2 × bore )2 × stroke × ncylinders
```

The stroke ratio, determined by dividing the bore by the stroke, traditionally indicated whether an engine was designed for power at high engine speeds (rpm) or torque at lower engine speeds.[2][3] The term "bore" can also be applied to the bore of a locomotive cylinder or steam engine pistons.

## Steam locomotive

The term bore also applies to the cylinder of a steam locomotive or steam engine.

## References

1. ^ Schwaller, Anthony (1999). Motor Automotive Technology. Delmar, New York
2. ^ "Square, Oversquare and Undersquare engines". www.motoetc.com. Retrieved 7 July 2019.
3. ^ "What Is Bore-Stroke Ratio and Square Engine Design?". www.carbiketech.com. 28 June 2017. Retrieved 7 July 2019.