Why Do Valves Open Early and Close Late?

[TheoMarie]

Intake valves open early to allow sufficient air to enter the cylinder. Exhaust valves close late to ensure that exhaust gases are expelled as much as possible after the power stroke. Below is relevant knowledge about valves: Increasing Intake Volume: The purpose of early intake valve opening is to achieve a larger valve opening at the start of intake, reducing intake resistance and ensuring smooth airflow. The purpose of late intake valve closing is to maximize the use of airflow inertia to increase intake volume. Reducing Residual Exhaust Gas: The purpose of early exhaust valve opening is to utilize the higher cylinder pressure during the initial exhaust phase for free exhaust, thereby reducing the resistance of forced exhaust and the power consumed during exhaust. The purpose of late exhaust valve closing is to fully utilize the inertia of exhaust gas flow to minimize residual exhaust gas.