During which phase of the engine cycle does the intake valve open?

The intake valve opens during the intake stroke of the engine cycle. During this phase, the piston moves down the cylinder, creating a vacuum that allows air-fuel mixture to be drawn into the combustion chamber. This process is crucial because it prepares the engine for the subsequent compression stroke, where the mixture is compressed to facilitate efficient combustion. Proper timing of the intake valve opening ensures that the maximum amount of the air-fuel mixture enters the cylinder, which is essential for the optimal performance of the engine. The coordination between the intake valve opening and the downward motion of the piston is vital for effective engine operation.