In Four-stroke petrol Engine, we use the Air-Fuel mixture and spark plug for the combustion process.
Everything will be the same as this valve timing except the fuel ignition principle. For the Four-stroke Petrol Engine also we can draw valve timing. We have discussed the valve timing diagram for the Four-Stroke Diesel Engine only. this will lead to the bad performance of the engine. similarly, if the engine Valve timing is not set correctly there is an exhaust blown or incomplete combustion. This is how the valve opening and closing action sequences are arranged in a Four Stroke Diesel Engine.Ī well-tuned Valve timing diagram will result in the better performance of the engine. Which means the useful amount of power generated during the power stroke will be lost due to the early opening of the exhaust valves. And the Exhaust valve closing should be maintained properly or otherwise, there is a chance of Exhaust Blowdown. Once the Piston reaches the Top dead centre, all the combustion particles will be thrown out of the cylinder completely and the suction stroke will start again for the second cycle.Īctual:In the actual cycle, the Exhaust stroke will start a bit early as before piston reaches the Bottom dead centre (BDC). At the BDC the exhaust valve will open, all the combustion particles will be thrown out of the cylinder with piston upward movement. Theoretical: In the theoretical Cycle, the expansion stroke has to start when the piston reaches the Bottom Dead Center (BDC) due to the power stroke.
#Valve timing diagram 4 stroke engine full
That is the way we can take the full advantage of the power stroke. So it has to start burning before the piston reaches to the TDC. But the reason behind injecting the fuel right before the piston reaches to the TDC is that the fuel complete combustion is not that instantaneous as like in the theoretical assumption. The ignition starts immediately right after the injection of the fuel into the cylinder. In which the piston is at the TDC.Īctual: In the actual Cycle, the fuel will be injected before the piston reaches to the top dead centre. Which is sufficient to self-ignite the fuel instantaneously which is injected at the end of the compression Stroke. Due to the high compression of the air in the cylinder, the pressure and temperature of the air are increased. Theoretical: In the theoretical Cycle, when the Piston reaches the Top Dead Center (TDC), Now the fuel is injected into the cylinder by the high-pressure fuel injector at the end of compression stroke. Because to close the valve completely, it will take some time. 360° of crankshaft rotation.Īctual: In the actual Cycle, The inlet valve starts closing right after the piston starts moving upward. These two strokes (i.e., suction and compression stroke) complete one revolution of the crankshaft.
The Air in the cylinder will be compressed. At this BDC The Inlet Valve will close, and the piston will start to move upward. Theoretical: In the theoretical Cycle, on completion of the suction stroke, The compression stroke starts when the piston reaches the Bottom Dead Center (BDC). so it has to be started opening a bit early. Because in the actual engine the valve cannot be open instantaneous. Actual: In the actual Cycle, the inlet valve will be started opening just before the piston reaching to the Top Dead Center (TDC) from the previous cycle.
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