compression ratio

American  

noun

Automotive.

1. the ratio of the cylinder volume enclosed by the piston at its outermost position to the volume enclosed by it at its innermost position.

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compression ratio British  

noun

1. the ratio of the volume enclosed by the cylinder of an internal-combustion engine at the beginning of the compression stroke to the volume enclosed at the end of it

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Etymology

Origin of compression ratio

First recorded in 1905–10

Example Sentences

From 1 June, the compression ratio will be measured at 130C as well as ambient temperature, and from next year only at 130C.

From BBC • Feb. 28, 2026

Because their rivals believe they have found a way of exploiting the rule restricting the compression ratio - a measurement of the cylinder displacement between the two extremes of the piston stroke - to 16:1.

From BBC • Feb. 20, 2026

Off track, one of the main focuses of pre-season has been a row between the engine manufacturers over the rules governing the engines' compression ratio.

From BBC • Feb. 20, 2026

The compression ratio is a measurement of the cylinder displacement between the two extremes of the piston stroke.

From BBC • Feb. 18, 2026

This seems low, considering the compression ratio and probable leakage past their rather weak piston rings, but it is possible.

From The Wright Brothers' Engines and Their Design by Hobbs, Leonard S.