102 ENGINE COMPONENT AND LOCATION The engine can be equipped with a Volvo engine brake system to assist in slowing the vehicle when necessary. The system includes the: Wiring harness Camshaft Oil control valve Exhaust rocker arms Engine brake rocker arms Exhaust valve yokes (bridges) There is a separate cam on the camshaft at each cylinder for the engine brake rocker arm. The lobes on this cam are timed to coordinate with the lobes on the exhaust valve cam. The exhaust rocker arm operates normally. When engaged, the engine brake rocker arm also operates the exhaust rocker arm. It causes the valve to open in a strategy to decrease cylinder power output.
Engine power is reduced assisting the brakes in slowing the vehicle. The engine brake rocker arms are equipped with a blade spring which keeps the rollers in contact with the cams. Volvo Engine Brake operation depends on all of the following conditions which must exist simultaneously. Accelerator pedal released Engine speed above 1100 rpm Clutch pedal released Road speed above 5 km/h (3.1 mph) ABS inactive Transmission in gear Oil temperature above 55°C (131°F) Charge air pressure above 50 kPa (7.25 psi) On the cylinder head, the oil control valve connects the oil passages in the head and rocker shaft. The oil pump produces constant pressure at this junction.
While the accelerator pedal is depressed, the control valve reduces the oil pressure in the rocker shaft to a minimum 100 kPa (14.5 psi).