What is the Principle of Exhaust Braking?

[LorenzoFitz]

Exhaust Braking Principle: Exhaust braking transforms the engine, originally a power output device, into an air compressor that becomes a power-consuming device. First, when the exhaust brake is activated, the fuel injectors stop spraying fuel, but the engine continues to operate, continuously drawing in fresh air. Simultaneously, the butterfly valve installed in the exhaust system closes, blocking the exhaust manifold, causing the pressure inside the exhaust manifold to reach 4 to 6 atmospheres. At this point, the engine's power source is the inertia force of the coasting vehicle, rather than the energy generated by combustion of the air-fuel mixture. The engine pistons are compressing the high-pressure air in the exhaust pipe, continuously consuming the kinetic energy of the moving vehicle, thereby achieving the goal of slowing down the vehicle.