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
compression ratio in American English
in an internal-combustion engine, the ratio of the largest volume to the smallestvolume of a cylinder, measured before and after the compressing action of the piston
compression ratio in Automotive Engineering
(kəmprɛʃən reɪʃoʊ)
Word forms: (regular plural) compression ratios
noun
(Automotive engineering: Vehicle components, Engine, transmission, and exhaust)
The compression ratio in an engine is the ratio of the volume of the cylinder plus combustion chamber at the bottom of the stroke (when the volume is greatest) to the volume at the top of the stroke (when the volume is least.)
This design has the facility to tilt the cylinder head slightly, so that the compression ratio can be altered automatically according to engine load and revs.
Not all engines have the same compression ratio, and an engine with a ratio set for a 95RON fuel will usually gain no benefit fromusing 98RON fuel since the pistons will not compress the fuel to its maximum.
To determine the compression ratio of an internal combustion engine, compare the greatest volume of the piston cylinderto the lowest volume.