In a four-stroke engine cycle, which step occurs last?

In a four-stroke engine cycle, the last step is the exhaust phase. This phase occurs after the power stroke, wherein the engine has converted the fuel into power and expelled exhaust gases. During the exhaust phase, the exhaust valves open, allowing the spent gases to exit the combustion chamber and be released into the atmosphere, making way for fresh air and fuel mixtures in the following intake stroke.

Understanding the sequence of the four-stroke cycle is crucial. The cycle consists of intake, compression, power, and exhaust, and knowing that the exhaust follows the power stroke helps clarify the functioning of the engine. After the engine has performed the work of the power stroke, it's essential to remove the waste gases to maintain efficiency and prepare for the next round of combustion in the cycle. This is why the exhaust phase is correctly identified as the last step in the four-stroke engine cycle.