What happens during the compression stroke of the engine?

• A. Air and fuel are mixed
• B. Air and fuel are compressed
• C. Burned gases are expelled
• D. The piston moves to BDC

Answer: (B)

During the compression stroke of the engine, the piston moves upward in the cylinder, which leads to the compression of the air-fuel mixture that has been drawn into the cylinder during the intake stroke. This compression increases the pressure and temperature of the mixture, preparing it for ignition. The higher pressure enhances the efficiency of combustion once the mixture is ignited by the spark plug, leading to a more powerful engine performance.

This process is critical because it ensures that the air-fuel mixture is dense and combustible, ultimately contributing to the overall efficiency and effectiveness of engine operation. Proper compression is essential for achieving optimal engine performance, fuel economy, and emissions control.