What occurs during the compression stroke?

During the compression stroke of an internal combustion engine, the piston moves upward within the cylinder. This upward movement occurs after the intake stroke, where the intake valve has opened to allow the air-fuel mixture to enter the cylinder. As the piston ascends, it compresses this mixture, preparing it for ignition.

The closing of the intake valve at the beginning of the compression stroke is crucial. This closure seals the combustion chamber, ensuring that the mixture is contained and can be compressed efficiently. As the piston reaches the top of its stroke, the compressed air-fuel mixture is then ignited, leading to the power stroke.

Understanding the role of the valves, particularly during this phase, is vital. The intake valve must be closed to maintain the compression needed for efficient combustion. This is why recognizing that the intake valve closes during the compression stroke is an important aspect of engine cycle knowledge.