What is the purpose of the top piston ring in a 4-stroke engine?

The primary function of the top piston ring in a four-stroke engine is to seal the combustion gases within the cylinder. This sealing is crucial for maintaining the necessary compression required for efficient combustion and optimal engine performance. By preventing the escape of gases during the power stroke, the top piston ring ensures that the engine can produce maximum power and efficiency.

Proper sealing also contributes to improved fuel economy and reduced emissions, as any leakage of combustion gases can result in incomplete combustion and increased pollutants. The design and material of the top piston ring help it withstand high temperatures and pressures associated with the combustion process, making it an essential component for maintaining the engine's overall functionality and longevity.