Valve Timing Diagram of Diesel Engine

Valve Timing Diagram for a Four Stroke Cycle Diesel Engine - The diesel engines are also known as compression ignition engines. The valve timing diagram for a four stroke cycle diesel engine is shown in Figure below:

The following particulars are important for a four stroke cycle diesel engine regarding valve timing diagram:

(a) The inlet valve opens at 10° — 20° before TDC and closes at 25° — 40° after BDC.

(b) The fuel valve opens at 10° — 15° before TDC and closes at 15°— 20° after TDC.

(c) The compression starts at 25° — 40° after BDC and ends at 10°— 15° before TDC.

(d) The expansion starts at 10° — 15° after TDC and ends at 30° — 50° before BDC.

(e) The exhaust valve opens at 30° — 50° before BDC and closes at 10° —15° after TDC.

Note: In diesel engines, the fuel is injected in the form of very fine spray into the engine cylinder, which gets ignited due to high temperature of the compressed air.


  1. what changs are required in the 4 stroke diesal engine


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