How is power obtained in a four-stroke petrol engine?

In a four-stroke petrol engine, power is obtained fundamentally through the process of combustion, which causes expansion of gases. In this cycle, the engine completes four distinct strokes: intake, compression, power (or expansion), and exhaust. During the power stroke, the air-fuel mixture is ignited, leading to an expansion of the gases within the combustion chamber. This rapid expansion exerts pressure on the piston, forcing it downward and effectively converting thermal energy from combustion into mechanical work.

This cycle of combustion and expansion is what drives the engine’s pistons and ultimately generates the power needed to move the vehicle. The efficiency of this process is critical to how effectively the engine translates fuel into power. Other factors like mechanical linkage, lightweight design, and air-fuel mixture efficiency do play roles in overall engine performance, but the primary mechanism for generating power in the four-stroke cycle is indeed the expansion caused by combustion.