Understanding Engine Compression Ratios

What is the compression ratio in an engine?

• The ratio of the volume of the cylinder when the piston is at the bottom to the volume when the piston is at the top.

• The ratio of the volume of the cylinder when the piston is at the top to the volume when the piston is at the bottom.

• The ratio of the fuel volume to the air volume in the cylinder.

• The ratio of the air volume to the fuel volume in the cylinder.

Which type of fuel is generally used in high compression ratio engines?

• Diesel

• Gasoline

• Ethanol

• Kerosene

How do you calculate the compression ratio of an engine?

What is a typical compression ratio for a gasoline engine?

• 6:1

• 10:1

• 15:1

• 20:1

What is a typical compression ratio for a diesel engine?

• 6:1

• 10:1

• 15:1

• 20:1

Which of the following is a characteristic of high compression ratio engines?

• They are less efficient.

• They produce more power.

• They require lower octane fuel.

• They have lower thermal efficiency.

Why do high compression ratio engines require higher octane fuel?

• To prevent knocking.

• To increase fuel efficiency.

• To reduce emissions.

• To increase engine temperature.

What is the effect of a low compression ratio on engine performance?

• Increased power output.

• Decreased fuel efficiency.

• Increased thermal efficiency.

• Reduced engine lifespan.

Which of the following is true about low compression engines?

• They are more efficient than high compression engines.

• They are less prone to knocking.

• They require high octane fuel.

• They produce more power than high compression engines.

If an engine has a cylinder volume of 500 cm³ at bottom dead center and 50 cm³ at top dead center, what is its compression ratio?

• 5:1

• 10:1

• 15:1

• 20:1