What is the reason for the early opening and late closing of the engine intake valve?

[Allison]

The reasons for the early opening and late closing of the intake valve are as follows: The purpose of early opening the intake valve is to have a larger opening or a larger intake cross-sectional area at the beginning of the intake process, thereby reducing intake resistance and ensuring smooth intake. Early opening and late closing are intended to increase the intake time and thus the intake volume. Increased intake volume enhances engine power, while also reducing harmful substances produced after combustion of the air-fuel mixture, such as nitrogen oxides and carbon monoxide. This helps improve emission standards and reduce environmental pollution. Late closing of the intake valve: This is to fully utilize the inertia of the airflow, continuing the intake during the intake lag angle to increase the intake volume. Reduced intake resistance not only increases the intake volume but also decreases the power consumed during the intake process.