What happens during the compression stroke of a four-stroke engine?

During the compression stroke of a four-stroke engine, the piston moves upward within the cylinder, compressing the air-fuel mixture that has been drawn in during the intake stroke. This compression is crucial because it raises the temperature and pressure of the mixture, making it more combustible. As a result, when the spark plug ignites the compressed mix at the end of the compression stroke, it leads to a powerful combustion event that drives the piston down during the power stroke.

The proper functioning of the compression stroke is essential for achieving efficiency and power in an engine. If compression is inadequate, it can lead to poor engine performance, misfires, and increased emissions. Therefore, understanding this step is fundamental to both engine mechanics and performance optimization.