Means of varying the compression ratio
Variable compression ratio engines

To change the compression ratio, equations and suggest changing the compression volume ratio. By assimilating compression ratio and compression ratio, equation shows that it is necessary to act either on the dead volume (volume of the combustion chamber), or on the unit displacement, or on both at the same time. The means used will be discussed in .

Although the analysis of theoretical internal combustion engine cycles assumes identical compression and expansion strokes, some engines have different strokes, such as the Atkinson engine. Furthermore, compression volume is generally considered to be the volume swept by the piston between its bottom dead center and top dead center positions. In the case of Miller's very late intake valve closure technique, the compression volume is taken to be...