8866A54 Mercruiser GEAR HOUSING ASSEMBLY

Illustration 1 g01113757
(1) Solenoid valve
(2) Valve connector
(3) Master cylinder
(4) Slave cylinder The Cat compression brake consists of three identical housing assemblies. Each housing assembly is positioned over two cylinders. The housing assembly is mounted to the supports for the rocker arm shaft with studs and nuts. The rocker arm and the exhaust bridge assembly is used to transfer force from slave piston (3) to the exhaust valves. The brake logic signal for the Cat compression brake is carried to solenoid valve (1) by the lead wire. This is done in order to activate the Cat compression brake on the two cylinders of the engine.The control circuit for the Cat compression brake permits the operation of either one, two, or all three of the compression brake housing assemblies. This provides progressive braking capabilities with the retarding effect of two cylinders, of four cylinders, or of all six cylinders in the engine.Operation of the Cat Compression Brake
Illustration 2 g01749075
Schematic for master-slave circuit
(5) Check valve
(6) High pressure oil passage
(7) Slave piston adjustment screw
(8) Master piston
(9) Actuator valve
(10) Oil drain passage
(11) Slave piston
(12) Master piston spring
(13) Spring for the slave piston
(14) Exhaust rocker arm
(15) Exhaust bridge
(16) Fuel injector rocker arm
(17) Rocker arm shaft oil passage
(18) Engine oil pump
(19) Engine oil pan
(20) Exhaust valve
(A) Actuation port
(T1) Drain port
(T2) Drain port
(P) Actuator spool for supply port The Cat compression brake is operated by engine oil that is distributed around the studs of the rocker shaft. This oil is supplied through the supports for the rocker shaft (16). Actuator valve (9) controls the oil flow in the compression brake housing.When the actuator valve is activated by a signal from the ECM, low pressure oil passes from the actuator spool supply port (P) to the actuation port (A). The oil flow opens the check valve (1) and flows into the high pressure oil passage (6). Oil is supplied to the slave piston (11) and the master piston (8). The oil pressure overcomes the spring (12) and the master piston moves toward the fuel injector rocker arm. Oil fills the passageway between the master piston and the slave piston. The master piston will follow the movement of the fuel injector rocker arm. The master piston moves upward with the fuel injector rocker arm. The movement of the master piston causes oil to close the check valve. The closed check valve causes pressure to increase in the hydraulic circuit of the master and slave piston.The slave piston is forced downward. The slave piston makes contact with the exhaust valve rocker arm. The slave piston continues to apply a force to the exhaust valve rocker arm. This force causes the exhaust valves to open. As the exhaust valves open the cylinder pressure is relieved through the open exhaust valves. This creates a net braking force at the flywheel.The fuel injector rocker arm continues to rotate and the master piston follows the motion. As the master piston moves downward the hydraulic pressure is decreased. The exhaust rocker arm completes the opening of the exhaust valves. The exhaust valves are returned to the closed position by the exhaust rocker arm. The slave piston is picked up by the exhaust rocker arm (14). The open check valve relieves the oil pressure. De-energizing the actuator valve allows the oil to drain from port (T1) and (T2). The exhaust valves close and the slave piston returns to the starting position.