What are the types of exhaust brakes?
2 Answers
Exhaust brakes can be categorized as follows: Throttle Control Braking: When deceleration is needed, maintain the 3rd gear position and fully release the throttle. At this point, the engine tends to idle, creating resistance in the drivetrain, which acts on the wheels to achieve deceleration. Exhaust Brake: In high-power diesel engines, there is a butterfly valve at the connection between the exhaust manifold and the exhaust pipe. When the vehicle is in gear, operating an electromagnetic switch closes the valve, causing the engine to stall and achieve a braking effect. The valve automatically opens when the throttle is pressed again. This method is structurally simple but can damage the engine. It is commonly used in heavy-duty trucks and large buses. Hydraulic Retarder: A turbine chamber is added at the rear end of the transmission housing. When the braking circuit is activated, transmission oil generates damping in the turbine to achieve braking. This method is wear-free but requires additional cooling. Currently, ZF transmissions use this technology in high-end buses.
Exhaust brakes mainly come in several types. When I drove heavy trucks, I frequently used butterfly valve exhaust brakes, variable nozzle turbo exhaust brakes, and electronically controlled exhaust brakes. The butterfly valve type is the most basic, manually switching a valve on the exhaust pipe to increase backpressure and assist in deceleration—simple and easy to use but noisy. The variable turbo type adjusts turbine blades to control exhaust flow, enabling smoother deceleration, suitable for modern diesel engines. The electronic control type relies on the ECU for automatic management, such as activating automatically during long descents or high braking demand to reduce brake wear. Each has its pros and cons: butterfly valves are cheap but prone to failure, while electronic versions are precise but costly to repair. The choice depends on driving habits and road conditions.
