Valve Timing & Vibration Damper MCQs with Detailed Explanation

Correct Answer: D

• Vibration damper reduces torsional vibration and crankshaft stress.
• It helps in reducing flywheel weight and increases crankshaft life.
• Vibration dampers are fitted at the front end of the crankshaft.
• So, the statement saying it is fixed at the rear end is incorrect.

Correct Answer: A

• The opening and closing of engine valves with respect to piston movement is called valve timing.
• Valves do not open or close exactly at the end of strokes.
• They open early and close late to fill the cylinder properly and remove burnt gases.
• Correct valve timing improves power output and efficiency.

Correct Answer: B

• Valve overlap is the period when both inlet and exhaust valves remain open together.
• It occurs near the end of exhaust stroke and beginning of suction stroke.
• This helps in scavenging exhaust gases.
• The incoming air-fuel mixture helps push out burnt gases from the cylinder.

Correct Answer: B

• Valve overlap helps in removing remaining burnt gases from the cylinder.
• This removal of exhaust gas is called scavenging.
• The momentum of incoming air-fuel mixture assists the exhaust gas flow.
• Better scavenging improves combustion and engine performance.

Correct Answer: B

• Valves are opened early and closed late because gas flow requires time.
• This helps the cylinder receive more fresh charge.
• It also helps burnt gases escape completely.
• This improves engine efficiency and power output.