22 ENGINE SYSTEMS
monitor EBP and adjust the duty cycle to the VGT to
match engine requirements.
VGT Control
Figure 15 VGT control
The VGT actuator is a control module that contains
a microchip and a DC motor. The VGT actuator
is located below the turbocharger. The microchip
operates a DC motor which rotates a crank lever
controlling the vane position in the turbine housing.
The position of the vanes is based off the pulse-width
modulated signal sent from the ECM.
Actuated vanes are mounted around the inside
circumference of the turbine housing. A unison ring
links all the vanes. When the unison ring moves,
all vanes move to the same position. Unison ring
movement occurs when the crank lever in the control
module moves.
Exhaust gas flow can be regulated depending on
required exhaust back pressure for engine speed
and load. As demand for EBP increases, the ECM
increases the pulse-width modulation to the VGT
control module. When EBP demand decreases, the
ECM decreases the duty cycle to the control module.
EGES-265-2
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
Follow all warnings, cautions, and notes.
© 2009 Navistar, Inc.
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