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Why Is The Intake Valve Larger Than The Exhaust Valve?

Jan. 10, 2020

The direct injection gasoline pressure must be greater than the pressure of the compressed gas so that the direct injection engine can smoothly inject fuel. This is the case with fuel injection, as is the case with air intake. Especially for naturally aspirated engines, when the cylinder pressure is large, there will be a certain loss of intake efficiency. So how does an engine engineer solve this problem?

For a four-valve engine, why is the diameter of the intake valve larger than that of the exhaust valve? Engine valve exporter shares with you.

Intake pressure: When the gas flows through the intake duct and the intake valve, it will be subject to resistance. In order to overcome these resistances and allow the mixture to flow at a certain speed, some pressure must be consumed. Therefore, the air pressure in the cylinder during the intake stroke is lower than the atmospheric pressure to ensure a sufficient air intake.

 Machinery Exhaust Valve

Gas density: When the air pressure in the cylinder decreases, the gas density also decreases, and the oxygen content in the combustible mixture is naturally lower. This will cause the combustion efficiency of the engine to decrease, and the power will be reduced.

Plateau pressure: In the plateau climate, the atmospheric pressure decreases, and the thin air oxygen content also decreases. At this time, the engine needs a larger amount of air intake to ensure the original rated power. The engine's plateau air intake efficiency needs to be considered in advance.

In short, in order to solve the above problems, engine designers have adopted increasing the area of the cross-section of the intake valve to solve the problem of intake efficiency. This is why we see that the diameter of the intake valve is larger than that of the exhaust valve.

Increasing the intake efficiency means that the cylinder can take in more air per unit time. If the fuel injection is appropriately increased, the engine power will naturally be higher. Increasing the diameter of the intake valve is a solution, and turbocharging is also a solution.

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