What is the primary purpose of the intake stroke in a four-stroke engine?

In a four-stroke engine, the primary purpose of the intake stroke is to obtain fuel and air for combustion. During this stroke, the piston moves down the cylinder, creating a vacuum that allows the air-fuel mixture to enter the combustion chamber through the open intake valve. This mixture is essential for the combustion process that will occur in the subsequent compression stroke.

The successful intake of the correct amount of air and fuel is critical for optimal engine performance, as it directly influences the combustion efficiency and power output of the engine. This process is essential in setting the stage for the subsequent compression, ignition, and power strokes that will follow in the engine cycle.