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Difference between throttle body on gasoline and diesel engines

throttle body

 Throttle body in Gasoline engine

The ratio A/F optimal for gasoline to burn completely in the engine combustion chamber is 14.7/1 (14.7 grams of air / 1 gram of gasoline). Therefore on gasoline engines will depend greatly on the amount of air intake.

ECM will calculate the amount of fuel injection based on the amount of air entering the engine, more air is injected, less air is injected, how to achieve the most optimal ratio.

But on gasoline engines, the throttle is the mechanism that controls the amount of air intake (the more open the throttle, the more wind comes in and opposite). For the above reasons, it can be said that the throttle valve on a gasoline engine is extremely important.

throttle body

 Throttle body  Diesel engine

For diesel engines, when operating, there is always a state of excess wind and the throttle is always open at the maximum position. When needing to accelerate, the accelerator pedal signal will be sent to the ECU and the ECU will control the injection volume to accelerate and opposite.

So what does the throttle body on a diesel engine do?

throttle body


  1. Diesel engine throttle helps reduce vibration when engine is off

– This can be said to be the first improved function for diesel throttle, when the engine is turned off, the ECM will control and close the throttle valve about 95 – 97% within 1.5 seconds, then it will limit the amount of wind entering the engine. The engine does not continue to charge and compress the air to make the engine turn off smoother.

  1. Assists in EGR valve flow control

– EGR (Exhaust Gas Recirculation) controls an amount of exhaust gas returned to the combustion chamber of the engine to reduce the combustion chamber temperature is an indispensable standard on both gasoline and diesel engines.

– The condition for exhaust gas to return to the intake manifold is that the intake air pressure must be less than the exhaust gas pressure, but in some cases the exhaust pressure is equal to or greater than the intake air pressure for example when the engine temperature is low. then the exhaust gas cannot return to the intake manifold.

At this time, the engine ECU will control to close the throttle from 5 to 94% to increase the vacuum after the throttle, that is to reduce the pressure in the intake manifold, when the intake air pressure is lower than the exhaust gas pressure, the exhaust gas will can return to the intake manifold.

  1. Reduces noise when air intake and vibration when idling

– Similar to the anti-vibration function when the engine is turned off, the throttle will open completely, then the intake air will continue to be sucked into the engine, leading to the engine’s quiet and noisy working condition, especially when idling.

– Therefore, the engine ECU will partially close the throttle valve in a certain time depending on the operating mode of the engine.

  1. Support in creating DPF filters

– The engine ECU will control close the throttle valve from 5 to 94% to reduce the amount of air intake. Less air intake combined with more fuel injection will result in a richer fuel/air ratio leading to a higher exhaust temperature to burn off all the soot in the DPF filters.

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