MBE 900 ENGINE 2007 OPERATOR'S GUIDE ENGINE BRAKE SYSTEM Certain MBE 900 vehicle engines are equipped with engine brakes, commonly referred to as retarders . Before operating the vehicle, you must familiarize yourself with the retarder system to obtain optimum benefit from it. Engine brake control systems may vary slightly, depending on the engine brake configuration and cab design. However, basic operator controls are similar for all models. The two systems operate independently of each other and in combination. Exhaust back pressure is used by the exhaust brake to increase braking performance.
The constant-throttle valves use the air that escapes through them on the compression stroke to provide braking force. The constant-throttles valves are small valves which are built into the cylinder head and positioned opposite the exhaust valve. When open, a link is created between the combustion chamber and the exhaust port. Exhaust Brake/Constant-Throttle Valves, Optional To increase braking performance, the engine can be equipped with an exhaust brake on the turbocharger in conjunction with constant-throttle valves in the cylinder head. See Figure 24. When the engine brake is switched on, the constant-throttle valves are put under pressure, which in turn opens the valves.
The constant-throttle valves are activated by engine oil pressure. The engine brake is activated by the CPC and can be activated only at engine speeds up to 2600 rpm. Below 900 rpm, the engine brake is always turned off to prevent the engine from stalling. Also, the engine brake is automatically turned off when the accelerator pedal is pressed. NOTE: When in emergency running mode (constant rpm), the engine brake can Figure 24 Constant Throttle Activation All information subject to change without notice. (Rev. 04/08) 55 DDC-SVC-MAN-0040 0704 Copyright © 2008 DETROIT DIESEL CORPORATION