Define compression ratio and displacement, and explain how each influences engine performance.

Define compression ratio and displacement, and explain how each influences engine performance.

• A. Compression ratio is the ratio of cylinder volume at bottom to top; displacement is the total swept volume of all cylinders. Higher compression improves thermal efficiency and power (up to limits); larger displacement increases available power/torque.
• B. Compression ratio equals engine displacement; displacement equals the ratio of bottom sensor readings to top. Higher compression reduces power; larger displacement reduces efficiency.
• C. Compression ratio measures intake air volume; displacement measures exhaust volume. Higher values reduce efficiency.
• D. Compression ratio is the same as displacement; both have no effect on performance.

Answer: (A)