Which formula is used to calculate the compression ratio of an engine?

The formula used to calculate the compression ratio of an engine is the sum of the clearance volume and the swept volume divided by the clearance volume. This calculation provides a numerical value that represents the relationship between the total volume of the cylinder when the piston is at the bottom of its stroke (bottom dead center) and the volume of the cylinder when the piston is at the top of its stroke (top dead center).

The clearance volume refers to the volume left in the cylinder when the piston is at its highest point, while the swept volume is the volume displaced by the piston as it moves between the highest and lowest points in the cylinder. By adding these two volumes together and then dividing by the clearance volume, the formula effectively assesses how much the air-fuel mixture is compressed in the cylinder during the engine's operation.

This ratio is crucial for understanding engine performance, efficiency, and the potential for knocking or detonation in combustion. Thus, the correct formula encapsulates the essential relationship between the volumes that define an engine's design and functionality.