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

Audi's entry this year rekindles that old rivalry with Mercedes, and battle lines have already been drawn in a pre-season row over the rules governing the engines' compression ratio.

From BBC • Feb. 27, 2026

Typically, the compression ratio reduces when engines heat up, and the belief was Mercedes had found a way using materials technology to limit this loss.

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

The compression ratio of this engine was lowered by almost 20 percent from that of the vertical 4.

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