Compression ratio
Combustion chamber capacity ratio

The compression ratio is the ratio between the maximum and minimum volume during the compression stage of the power cycle in a piston or Wankel engine. A fundamental specification for such engines, it can be measured in two different ways. The simpler way is the static compression ratio: in a reciprocating engine, this is the ratio of the volume of the cylinder when the piston is at the bottom of its stroke to that volume when the piston is at the top of its stroke. The dynamic compression ratio is a more advanced calculation which also takes into account gases entering and exiting the cylinder during the compression phase.
This brief starts where responsible research should: with the source description of “Compression ratio” as combustion chamber capacity ratio. Everything that follows is an evidence route, not borrowed authority.
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This entry incorporates text from “Compression ratio” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.