Valve Timing Diagram for four stroke petrol engine

Valve Timing Diagram

*20^o-35^o -35^o -35^o -10^o 
Inlet Valve:

Inlet Valve opens (IVO) 20^o before the piston reaches TDC and sucks air-fuel mixture and closes (IVC) 35^o after BDC.

After inlet valve closes, the piston compresses the mixture from BDC to TDC.

During the compression stroke, the Ignition occurs at an angle of 35^o before the piston reaches to TDC.

After Ignition, the mixture combusts and expands. During this stage, the piston moves from TDC to BDC.

Exhaust Valve:

After the expansion stage, the Exhaust valve opens (EVO) before 35^o the piston reaches to BDC.

The combusted gas escapes through exhaust valve completely during the repeated compression stroke.

The Exhaust Valve closes (EVC) 10^o after the TDC of combustion chamber.

*Again the Inlet valve Opens (IVO) 20^o before Closing the exhaust valve (EVC)

This continues a repeated Cycle

Note:  (20^o-35^o -35^o -35^o -10^o) are the angles made by  crankshaft rotation.



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