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

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

From BBC • Feb. 28, 2026

Red Bull's position on the compression ratio argument has not been clear until now, following their entry as a power-unit manufacturer this season.

From BBC • Feb. 18, 2026

Audi, Ferrari and Honda have complained to governing body the FIA because they believe Mercedes have found a loophole in the rule regarding compression ratio.

From BBC • Feb. 2, 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.