Navistar International DT 466 Diagnostic/Troubleshooting Manual page 26

22
VGT Closed Loop System
Figure 13 VGT closed loop system
The Variable Geometry Turbocharger (VGT) is a
closed loop system that uses the Exhaust Back
Pressure (EBP) sensor to provide feedback to the
ECM. The ECM uses the EBP sensor to continuously
monitor EBP and adjust the duty cycle to the VGT to
match engine requirements.
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
1 ENGINE SYSTEMS
VGT Control
Figure 14
The VGT actuator is a control module that contains
a microchip and a DC motor.
is located below the turbocharger.
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-270-1
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
VGT control
The VGT actuator
The microchip