Valve timing refers to the precise timing of when the engine's valves open and close during the combustion cycle. This timing is crucial for optimizing engine performance, efficiency, and emissions. Proper valve timing ensures that the air-fuel mixture enters the combustion chamber at the right moment and that exhaust gases exit effectively. In internal combustion engines, camshafts control valve timing. The design and adjustment of these camshafts can significantly impact an engine's power output and fuel economy. Advanced systems, like variable valve timing, allow for real-time adjustments to improve performance across different engine speeds and loads.