PREVOST LE MIRAGE XLII BUS SHELLS User Manual

1.29 JAKE BRAKE
The blowdown of compressed air to atmospheric pressure prevents the return of energy to the
engine piston on the expansion stroke, the effect being a net energy loss, since the work done in
compressing the cylinder charge is not returned during the expansion process.
Exhaust blowdown occurs as the energized solenoid valve permits engine lube oil to flow under
pressure through the control valve to both the master piston and the slave piston. See Figure 1-415.
Oil pressure causes the master piston to move down, coming to rest on the injector rocker arm
roller.
The injector rocker arm begins its travel as in the normal injection cycle, moving the master piston
upward and directing high-pressure oil to the slave piston. The ball check valve in the control
valve traps high-pressure oil in the master-slave piston system.
High pressure oil causes the slave piston to move down, momentarily opening the exhaust valves,
while the engine piston is near its top-dead-center position, releasing compressed cylinder air to
the exhaust manifold.
At the bottom of its stroke, the slave piston separates from the valve in the slave piston adjusting
screw, allowing high pressure oil to flow into the accumulator. This reduces the pressure in the
high pressure circuit, permitting the slave piston to retract and the exhaust valves to close in
preparation for the normal exhaust valve cycle. The oil pressure reserved in the accumulator
ensures that the hydraulic circuit is fully charged for the next cycle. Compressed air escapes to the
atmosphere, completing a compression braking cycle.
All information subject to change without notice.
1-526 From Bulletin 16-60-99 6SE483 9901 Copyright © 1999 DETROIT DIESEL CORPORATION

PREVOST LE MIRAGE XLII BUS SHELLS Specifications

General

Brand	PREVOST
Model	LE MIRAGE XLII BUS SHELLS
Category	Buses
Language	English