54 1 ENGINE SYSTEMS
driving c on ditions. See vehicle Operator’s Manual for
complete operating instructions.
Engine Brake Concept
The engine brake system retards vehicle speed
during deceleration or braking. During deceleration
and braking, the vehicle wheels drive the engine; the
engine acts as an energy absorber.
Engine Brake Operation
To absorb energy, the Diamond Logic® engine brake
combines bleeding off compressed intake air, VGT
controlling exhaust back pressure, and vehicle driven
piston movement.
• Energy is absorbed during the compression
stroke, when intake air is compressed and forced
through a slightly open exhaust valve, providing
compressed air flow to the V GT.
• VGT turbine vanes create the desired energy
absorbing, back pressure and intake boost.
• Atthetopofthecompressionstrokeenergy
dissipates, pressure to force the piston down is
eliminated, and energy is absorbed by the vehicle
drive pulling the piston down.
Engine Brake Control
Figure 46 High-pressure oil rail
1. High-pressure oil rail
2. ICP sensor
3. Brake shut-off valve assembly
4. BCP sensor
5. Brake pressure relief valve
6. Fr ont of engine
The high-pressure oil rail uses high-pressure oil from
the injection control pressure system to open exhaust
valves.
EGES-270-1
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
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