Engine Braking: A Perspective in Terms of Brake Power

Engine braking is a supplemental retarding technology in addition to foundational friction brakes in commercial vehicles. This technology is in use in Europe & Americas for several decades now. In engine braking, the engine acts as a compressor, thus producing the required braking power. The braking power is generated by either reducing the volumetric efficiency or increasing the pressure difference across the cylinder. This is usually achieved by means of exhaust valve lift modulation. There are dominantly two types of engine brakes viz. bleeder brake and compression release brake. The present work uses GT-Power® model to study the braking performance of a 4-cylinder, medium duty diesel engine at different engine RPMs and valve lifts. The work brings out a comprehensive understanding of different lift events and their effects on braking performance. The study further emphasizes on the brake power requirements from vehicle perspective at different tonnage, downgrades and vehicle speeds. Vehicle brake power requirements and brake power produced by each brake technology is mapped together to understand the operating range of each brake technology, which thus helps the vehicle manufacturer to choose appropriate technology for their platform.