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Principle of Diesel Engine Exhaust Brake Control

Dec. 15, 2023

The application of exhaust braking on large cargo vehicles has high pressure, obvious braking effect, and does not require other media. It is widely used in modern automobiles (commercial vehicles and large passenger cars). The exhaust braking device consists of an exhaust braking button valve, an exhaust working cylinder, an exhaust braking butterfly valve, and a stop oil and gas system, as shown in the following figure. The exhaust brake operation is convenient, simple and effective. When driving on ice, snow, and slippery muddy roads, using exhaust brakes can reduce sideslip. When driving downhill on long slopes, using exhaust brakes can reduce the number of driving brakes, lower the temperature rise of the brake drum, and improve the reliability of braking. When using exhaust braking, it can reduce the supply of diesel generator fuel and even cut off fuel, which can save fuel.


diesel engine


When the driver uses the exhaust brake, they step on the exhaust brake button on the bottom left of the cab floor with their feet. The button valve is forced to open the air channel, and compressed air enters the exhaust working cylinder. The piston of the exhaust working cylinder moves under the pressure of compressed air, driving the push rod. The push rod drives the exhaust brake disc, and the butterfly valve rotates to block the exhaust pipe. At the same time, compressed air enters the oil stop cylinder when the button valve is opened. The piston of the oil stop cylinder moves under the action of compressed air, and the push rod drives the governor handle through the linkage mechanism to stop the supply of oil. Due to the blockage of the exhaust pipe, the diesel engine stopped exhaust, fuel supply was interrupted, and the pressure in the exhaust pipe reached 0.3-0.4 MPa. The exhaust stroke of the diesel generator piston during operation must overcome this pressure, greatly increasing the braking power of the diesel engine. Therefore, when using exhaust braking, when the diesel engine piston is in the exhaust stroke of the diesel generator, the piston is subjected to the back pressure of the gas, which is transmitted to the wheels through the crankshaft and transmission system, increasing the rotational resistance of the wheels and reducing the vehicle speed.


When the pressure inside the exhaust manifold reaches a certain value, it overcomes the resistance of the valve spring, opens the exhaust valve, compresses air into the cylinder, and is discharged by the intake pipe to ensure that the pressure inside the exhaust manifold does not continue to rise. At this point, the diesel engine emits a special sound. Some drivers believe that using exhaust braking is harmful to diesel engines, and this view has no scientific basis.


When using exhaust braking, due to the cessation of fuel supply, the diesel engine essentially becomes an air compressor to consume energy and control vehicle speed. At this time, although the fuel supply to the diesel engine is stopped, the lubrication and cooling system of the diesel engine is still working normally, only changing from outputting energy to consuming energy. During operation, attention should be paid to the integrity of all components of the exhaust braking device. If there is any damage, it should be repaired or replaced.


Dingbo Power was founded in 1974 and is one of the earliest manufacturers of generators and diesel generator sets in China. If you want get more information, please feel free to send email to sales@dieselgeneratortech.com we will pay highly attention on your question.

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