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

Mercedes' rivals were pushing for the compression ratio to be measured at operating temperature.

From BBC • Feb. 28, 2026

Formula 1's governing body the FIA said on Saturday that a change to the way the compression ratio was measured would be introduced on 1 June, with a further revision for the 2027 season.

From BBC • Feb. 28, 2026

Mercedes' rivals have complained to governing body the FIA that the former champions have found a way to circumvent the rules regarding compression ratio.

From BBC • Feb. 9, 2026

Audi, Honda and Ferrari fear Mercedes have found a way to exploit the way materials expand with heat to have the engines running to a higher compression ratio when the car is on track.

From BBC • Feb. 9, 2026

Table III., giving the theoretical thermal efficiency for these three symmetrical cycles of constant temperature, pressure and volume, extends from a compression ratio of � to 1⁄100th.

From Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 4 "G" to "Gaskell, Elizabeth" by Various