What is the purpose of the compression release in an engine?

The purpose of the compression release in an engine is primarily to facilitate easier starting. In engines, particularly small engines like those found in lawn mowers or chainsaws, high compression can make it difficult to start the engine, especially when cold. The compression release temporarily decreases cylinder pressure during the starting phase. By easing the load on the starter motor and reducing the effort needed to turn the engine over, it allows for smoother and easier starting.

This mechanism is particularly beneficial in two-stroke engines or larger four-stroke engines that require significant force to overcome the compression when starting. Once the engine begins to run, the compression release typically disengages, allowing the engine to operate at normal compression levels for effective performance and power generation.