What is the relationship between the intake stroke and the use of valves?

During the intake stroke of a four-stroke engine, the intake valve must be open to allow the air-fuel mixture to enter the combustion chamber while the piston moves downwards. This stroke is critical for drawing in the necessary mixture for combustion in the next cycle. The exhaust valve, on the other hand, remained closed during this phase to maintain cylinder pressure and ensure that the incoming mixture does not escape.

When the intake valve is open, it creates a vacuum that draws the air-fuel mixture into the cylinder. If the exhaust valve were open at this time, it would disrupt the intake process, causing loss of pressure optimization and potentially leading to poor performance or incomplete combustion. The careful timing of the opening and closing of the valves is crucial for efficient engine operation and is governed by the engine’s camshaft design.

In this context, it is clear why the relationship between the intake stroke and valve operation is essential. The intake valve is open while the exhaust valve is closed, allowing the engine to effectively prepare for the power stroke that follows. This coordination of valve operation is a foundational concept in small engine technology, helping to ensure the engine runs smoothly and efficiently.