valve timing

In engineering, valve timing refers to the precise moments when a valve opens and closes within an internal-combustion engine. This process is crucial for the engine's operation, particularly in a four-stroke cycle. The camshaft, driven by the crankshaft, features cams that actuate the intake and exhaust valves. The camshaft typically rotates at half the speed of the crankshaft to ensure synchronization with piston movement.

The four-stroke cycle involves:
* Intake: The inlet valve opens, allowing the air-fuel mixture into the cylinder as the piston moves down.
* Compression: The inlet valve closes, and the piston moves up to compress the mixture.
* Power: The mixture is ignited, forcing the piston down and generating power.
* Exhaust: The exhaust valve opens, and the piston moves up to expel gases.

Modern engines often use variable valve timing to optimize valve operation across different engine speeds, improving performance, fuel efficiency, and reducing emissions.12