In a four-stroke tractor diesel engine, the 'valve overlap' period refers to the crank rotation angle during which:
Options:
(A) Both the inlet valve and exhaust valve remain open simultaneously around Top Dead Center (TDC)
(B) Both valves remain closed throughout the compression stroke
(C) Fuel injection occurs while the exhaust valve is fully open
(D) Both valves remain open simultaneously around Bottom Dead Center (BDC)
Answer Key:
A
Step-by-Step Solution & Explanation
Valve overlap occurs when the intake valve opens before TDC (inlet lead) while the exhaust valve is still closing after TDC (exhaust lag). This utilizes the momentum of the outgoing exhaust gas column to scavenge clearance volume and draw in fresh air.