In the four-stroke power cycle, what is the term for the up motion of the piston?

In the context of the four-stroke power cycle, the up motion of the piston during the compression stroke is crucial. During this phase, the piston moves upward in the cylinder, compressing the air-fuel mixture that has been drawn in during the intake stroke. This compression raises the mixture's temperature and pressure, which is essential for efficient combustion when the spark plug ignites the mixture.

The compression stroke is vital because it prepares the air-fuel mixture for combustion, resulting in a more powerful explosion when ignited, leading to greater engine efficiency and performance. This step directly affects the engine’s overall power output and efficiency, making it foundational to the functioning of an internal combustion engine.

This is distinct from the other strokes in the cycle: the power stroke is when the piston is pushed down by the expanding gases after ignition, the exhaust stroke is when the piston moves upwards to expel burnt gases, and the intake stroke involves the piston moving down to draw in the air-fuel mixture. Each stroke serves a specific role, but the compression stroke is characterized by the upward movement of the piston that prepares for combustion.