1. Exhaust Valve Control: The engine retarder brake system involves modifications or additions to the engine's exhaust system. It incorporates a variable exhaust valve timing system or an exhaust valve actuator.
2. Retarder Valve Activation: When the driver engages the engine retarder brake, the exhaust valve control system activates. The exhaust valves are opened at specific intervals during the engine's compression stroke.
3. Compression Braking: As the exhaust valves open, the compressed air and partially burnt fuel from the combustion chamber are released into the exhaust system. This causes a sudden drop in cylinder pressure and a reversal of the airflow. The engine's compression is no longer pushing the piston down but is instead working against it.
4. Heat Dissipation: The rapid release of the compressed air creates heat, which is dissipated through the engine's cooling system.
5. Resistance and Braking Effect: The resistance created by the engine's compression stroke trying to drive the piston against the outflowing air acts as a braking force on the vehicle. The engine's rotational speed is slowed down, and this in turn slows down the vehicle's speed.
6. Adjustable Braking Power: The engine retarder brake system can have different levels of braking power. The driver can select the appropriate level based on the vehicle's weight, road conditions, and desired level of deceleration.
7. Automatic Activation: Some engine retarder brake systems are designed to activate automatically when the vehicle exceeds a certain speed or when a specific gear is engaged. This helps maintain a safe speed without requiring constant manual intervention from the driver.
Engine retarder brakes are particularly useful in heavy-duty vehicles descending long slopes or mountain roads, where the risk of overheating the regular wheel brakes is high. They are more effective than traditional friction brakes in reducing wear on the brake components and providing additional control over the vehicle's speed.
