During the first piston stroke, what occurs in the engine?

During the first piston stroke, the primary function of the engine's piston is to create a vacuum that draws the fuel/air mixture into the combustion chamber. This phase is often referred to as the intake stroke. As the piston moves downward within the cylinder, it reduces the pressure inside, allowing the fuel and air to enter from the intake manifold through the open intake valves. This mixture is essential for the combustion process that will occur in subsequent strokes, specifically after the piston compresses it and the spark plug ignites it.

Understanding this process is crucial for grasping how internal combustion engines operate, as each stroke has a specific role that contributes to the overall performance and efficiency of the engine.