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

See Examples For:

compression ratio

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

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

Rivals believe Mercedes have found a loophole that allows them to run the engine above the permitted compression ratio.

From BBC ● Feb. 11, 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

For instance, an engine with a compression ratio of one-third has an air-standard efficiency of 0.36, and the actual indicated efficiency of a well-designed engine should be .36 multiplied by .7 = 0.25.

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