CONNECTION AS 2169743 - Caterpillar

The compression brake is powered from the ECM. The compression brake helps the operator to slow the vehicle on grades, in curves, or for a necessary speed reduction. The service brakes should not be used continuously on long descending grades. The service brakes are assisted by the compression brake. The engine crankshaft is turned by the rear wheels during downhill operation or during any slow down condition. The engine crankshaft is turned through the differential, through the drive shaft, through the transmission, and through the clutch. An application of a braking force can be made to the engine piston in order to reduce the speed of the vehicle.When the compression brake is activated, braking power is accomplished by opening the engine's exhaust valves. The exhaust valves are opened near the top of the compression stroke in order to release the highly compressed air into the exhaust system. The compression brake can only be activated when the engine is in the no-fuel position. Thus, combustion does not occur and no positive force is produced on the piston. The compressed air pressure that is released to the atmosphere prevents the energy from returning to the engine piston on the power stroke. The result is a loss of energy since the work that is done by the compression of the cylinder charge is not returned by the expansion process. This loss of energy is taken from the rear wheels. The rear wheels provide the braking action for the vehicle.
Illustration 1 g00501265
Compression brake (1) Control valve (2) Lead wire (3) Bolt assembly (4) Slave piston (5) Solenoid valve (6) Master piston (7) Stud and nutThe compression brake consists of three identical housing assemblies. A housing assembly is installed in each of the valve mechanism compartments above the rocker arms and above the rocker arm shaft. 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 (7). The housing assemblies are supported on the cylinder head with bolt assembly (3). The exhaust bridge assembly is used to transfer force from slave piston (4) to the exhaust valve. The brake logic signal for the compression brake is carried to solenoid valve (5) by lead wire (2). This is done in order to activate the compression brake on the two cylinders of the engine.A spacer is used on the top of the valve cover base in order to provide space for the installation of the compression brake and of the valve cover. When the compression brake is installed, the height increases approximately 63.5 mm (2.50 inch).The control circuit for the 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.Performance of the Compression Brake
Illustration 2 g00427859
Performance of the compression brakeThe performance of the compression brake, which is shown in the graph,