During the power stroke, what acts against the cylinder wall due to expanding gases?

During the power stroke in a four-stroke engine, the combustion of the air-fuel mixture leads to the rapid expansion of gases inside the cylinder. As these gases expand, they exert pressure against all surfaces of the cylinder, particularly against the top ring of the piston. This pressure causes the piston to move downwards in the cylinder, converting the chemical energy from the fuel into mechanical energy as it generates power for the engine.

The top ring on the piston is designed to create a seal and withstand the pressures generated during the combustion process. Its position and design allow it to effectively transfer the force from the expanding gases to the piston and subsequently to the crankshaft, enabling the engine to convert this energy into rotational motion.

In contrast, elements like the crankshaft, engine oil, and flywheel do not directly respond to the expanding gases in the same manner as the top ring on the piston. The crankshaft transmits the power generated by the moving piston but does not act against the cylinder wall. Engine oil lubricates components without being directly involved in the power generation process. The flywheel serves to smooth the delivery of power but, again, does not directly interact with the cylinder wall in the context of the power stroke.

Thus, the top ring