Where in the cylinder is wear greatest during normal operation?

Where in the cylinder is wear greatest during normal operation?

• A. Near the top of the cylinder
• B. Near the bottom of the cylinder
• C. Mid-stroke region
• D. Near the spark plug area

Answer: (A)

The region closest to the combustion chamber experiences the greatest wear. During normal operation, the hottest, highest-pressure gases are generated at the top of the bore as the fuel-air mixture ignites and the piston is near top dead center. The piston rings ride against the bore in this hot, turbulent zone, and the oil film can break down under such heat and chemical exposure. That combination of high temperature, high pressure, and challenging lubrication accelerates wear most where the combustion chamber is located—the upper portion of the cylinder. The bottom and mid-stroke regions stay cooler and under less pressure, so wear there is less. The top region—including the area around the spark plug—is where these harsh conditions concentrate, making wear greatest there.

The region closest to the combustion chamber experiences the greatest wear. During normal operation, the hottest, highest-pressure gases are generated at the top of the bore as the fuel-air mixture ignites and the piston is near top dead center. The piston rings ride against the bore in this hot, turbulent zone, and the oil film can break down under such heat and chemical exposure. That combination of high temperature, high pressure, and challenging lubrication accelerates wear most where the combustion chamber is located—the upper portion of the cylinder. The bottom and mid-stroke regions stay cooler and under less pressure, so wear there is less. The top region—including the area around the spark plug—is where these harsh conditions concentrate, making wear greatest there.