DESCRIPTION AND OPERATION
Page 27
VARIABLE TURBINE GEOMETRY (VTG)
TURBOCHARGER
The ASET™ AC (CEGR) engine is equipped with
a variable geometry turbocharger. The assembly
can be identified by the larger turbine housing
and actuator assembly (Figure 16). The turbine
housing has a set of variable position vanes that
maintain sufficient back-pressure in the exhaust
manifold for proper operation of the EGR system.
A certain amount of back-pressure is required to
push the exhaust gases into the pressurized
intake air at the EGR mixer. A sensor on the
actuator monitors vane position and provides
input to the EECU for control of vane position and
exhaust back-pressure.
There are several replacement parts available for
the VTG turbocharger. Available service parts are
as follows:
앫 VTG Actuator and Position Sensor
Assembly
앫 Turbo Wheel Speed Sensor
앫 VTG Actuator Flange-to-Turbine Housing
Allen-Head Bolts
앫 VTG Actuator Clevis Pin and Pin Retaining
Clip
16
Figure 16 — VTG Turbocharger
In operation, modulated air pressure applied to
the actuator closes the vanes. As the vanes
close, the exhaust gases flow faster through a
smaller opening to increase turbine shaft/wheel
speed as well as increasing exhaust
back-pressure. The EECU can then open the
vanes as required to control back-pressure in the
system.
17
Figure 17 — Turbocharger Turbine Vanes
1. VTG Vane Actuator
2. Actuator Air Line
3. Vane Position Sensor
4. Wheel Speed Sensor
5. Thermal Isolation Plate
6. Vane Position Sensor
Module
1. Turbine Housing 2. Turbine Vanes
5-111.bk Page 27 Monday, July 10, 2006 2:26 PM
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