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The role of the engine brake is to convert a power-producing engine into a power-absorbing retarding mechanism. Modern heavy-duty vehicles are usually equipped with a compression braking mechanism that augments their braking capability and reduces the wear of the conventional friction brakes. This work presents an engine brake mechanism modeling and design based on decompression effect, obtained by exhaust valve opening during the end of the intake cycle. Besides that, during the system operation the emissions are drastically reduced, even eliminated, since there is no fuelling, contributing to pollution level reductions. In this sense, this work describes a development of such engine brake system for a 4 and a 6 cylinder diesel engines. The engine brake performance was predicted by the development of 1D engine models.

The need for braking capacity improvement has a negative impact as it increases the loads acting on the conventional brake system, increasing wear between its components and requiring a more robust design. Looking this scenario, an available option is to use the engine as a source of braking power. Some conventional engine brake systems consume the vehicle/engine inertia power through the exhaust system closing (total or partial). However, the braking efficiency of this version is limited by bouncing occurrence on the exhaust valves, generating stronger impact of valve and valve seat. The developed solution consists in creating an engine brake mechanism acting directly on the exhaust valve, achieving greater efficiency. The mechanism is based on a hydraulic actuator positioned between the exhaust rocker arm and the valve stem top.