Abstract: The relatively complex and expensive "control valves", which are conventionally used in certain compression release engine brakes for such purposes as filling, isolating, and venting the high pressure portions of the hydraulic circuits in the engine brake, are eliminated and more direct means are provided for performing these functions. In brakes having a mechanism for resetting each slave piston, the high pressure portion of the circuit is filled through a selectively openable aperture in the slave piston. In brakes having a mechanism for automatically adjusting slave piston lash or for limiting ("clipping") the forward stroke of the slave piston, high pressure circuit fill is provided through a simple check valve. In systems in which hydraulic fluid is temporarily displaced from the high pressure circuit, a simple accumulator is provided to store hydraulic fluid for quick refill. A single such accumulator may replace multiple control valves.

Abstract: In a compression release engine brake, each slave piston has an associated mechanism for both automatically adjusting the "lash" of the slave piston and for resetting the slave piston as soon as the slave piston has produced a compression release event and without needing to wait for the return stroke of the associated master piston. The mechanism preferably includes two nesting cups between an adjusting member and the slave piston. The inner cup is principally responsible for the lash adjusting function, while the outer cup is principally responsible for the slave piston resetting function.