Valve timing diagram

Valve timing diagram is one of the most important topic about engine. This gives u the idea about how engine's valves should open and close. Knowing this u can make your engine more efficient and effective.

1. VALVE TIMING DIAGRAM Presented To: Mr. Dinesh Kumar Presented By: Md Nooruddin B.Tech (Mech.), 5 th Sem MUR1800575

2. CONTENTS Introduction Why we n eed Valve Timing Diagram ? Theoretical Valve Timing Diagram For Four Stroke Engine For Two Stroke Engine Actual Valve Timing Diagram For Four Stroke Engine For Two Stroke Engine Theoretical vs Actual Valve Timing Diagram

3. Valve timing diagram A valve timing diagram is a graphical representation of the opening and closing of the intake and exhaust valve of the engine . The valve timing diagram comprises of a 360 degree figure which represents the movement of the piston from TDC to BDC in all the strokes of the engine cycle, Which is measured in degrees and the opening and closing of the valves is controlled according to these degrees .

4. Why we need Valve Timing Diag. ? The normal engine completes around 100000 cycles per minute, as we know there are number of processes involve in a single cycle (from the intake of the air-fuel mixture to the exhaust of the combustion residual) of a internal which makes it necessary to be equipped with an effective system that can enable – Ideal timing for the opening and closing of the inlet and outlet valve which in turn protect the engine from defects like knocking or detonation. A high compression ratio required to combust the fuel especially in case of diesel engine by overlapping the closing of the valve. Synchronisation between the steps of a cycle of the engine from intake of air-fuel ratio to the exhaust of combustion residual.

5. 1. For Four-stroke Cycle Engine : Theoretical Valve Timing Diagram

6. 1. For Two-stroke Cycle Engine : Theoretical Valve Timing Diagram

7. A. Petrol /Spark Ignition Engine (SI Engine) - TDC : Top Dead Centre BDC : Bottom Dead Centre IVO : Inlet valve opens ( 10 - 20 before TDC ) IVC : Inlet valve Closes( 30 - 40 after BDC ) IGN : Ignition ( 20 - 30 before TDC ) EVO : Exhaust valve opens( 30 - 50 before BDC ) EVC : Exhaust valve Closes( 10 - 15 after TDC ) 1. For Four-stroke Cycle Engine : Actu al Valve Timing Diagram

8. B . Diesel /Compressed Ignition Engine (SI Engine) - 1. For Four-stroke Cycle Engine : Actu al Valve Timing Diagram TDC : Top Dead Centre BDC : Bottom Dead Centre IVO : Inlet valve opens ( 10 - 20 before TDC ) IVC : Inlet valve Closes( 25 - 40 after BDC ) FVO : Fuel Valve Op ens ( 10 - 15 before TDC ) FVC : Fuel Valve Closes ( 15 - 20 after TDC ) EVO : Exhaust valve opens( 39 - 50 before BDC ) EVC : Exhaust valve Closes( 10 - 15 after TDC )

9. 1. For Two-stroke Cycle Engine : Actu al Valve Timing Diagram TDC : Top Dead Centre BDC : Bottom Dead Centre EPO : Exhaust Port opens( 35 - 50 before BDC ) T P O : Transfer port opens ( 30 - 40 before BDC ) TPC : Transfer Port Closes( 30 - 40 after BDC ) EPC : Exhaust port Closes( 35 - 50 after TDC ) IGN : Ignition ( 1 5 - 20 before TDC ) A. Petrol /Spark Ignition Engine (SI Engine) -

10. 1. For Two-stroke Cycle Engine : Actu al Valve Timing Diagram TDC : Top Dead Centre BDC : Bottom Dead Centre F VO : Fuel valve opens ( 10 - 15 before TDC ) F VC : Fuel valve Closes( 15 - 20 after TDC ) EPO : Exhaust Port Op ens ( 35 - 50 before BDC ) TPO : Transfer Port Op ens( 30 - 40 before BDC ) TPC : Transfer Port Closes( 30 - 40 after BDC ) EPC : Exhaust Port Closes( 35 - 50 after BDC ) B . Diesel /Compressed Ignition Engine (SI Engine) -

11. Actual vs Theoretical Valve Timing Diagram Sr. No. Actual Valve Diagram Theoretical Valve Timing 1. The inlet valve starts opening 10 degrees to 30 degrees before the beginning of suction stroke (TDC) and closes after 30 degrees to 40 degrees at the end of the stroke (BDC) The inlet valve opens exactly at the beginning of suction stroke (TDC) and closes at the end of the stroke (BDC) 2. The exhaust valve starts opening 30 degrees to 60 degrees before the beginning of exhaust stroke (BDC) and closes after 8 degrees to 10 degrees at the end of the stroke (TDC) The exhaust valve opens exactly at the beginning of exhaust stroke (BDC) and closes at the end of the stroke (TDC) 3. The inertia of the valve operating mechanism is considered Inertia of the valve operating mechanism is not considered 4. Time for the charge to fill completely into the cylinder is considered Time for the charge to fill completely into the cylinder is not considered 5. Time for the exhaust gases to escape out of the cylinder is considered Time for the exhaust gases to escape out of the cylinder is not considered 6. The inlet valve is closed when the piston reaches a point in its next stroke at which the pressure in the cylinder equals the pressure outside. The inlet valve is closed when the piston reaches TDC 7. The valves are opened or closed slowly. The valves are closed or opened instantaneously 8. There is valve overlap. There is no valve overlap.