20
ENGINE SYSTEMS
Variable Geometry Turbocharger (VGT)
Figure 13 VGT
1.
Actuator
2.
Control valve
3.
Unison ring
4.
Vanes
The
key
feature
of
the
Variable
Geometry
Turbocharger (VGT) is the introduction of adjustable
vanes within the turbine housing to modify the flow
characteristics of exhaust gases onto the turbine
wheel. The net benefit is to provide optimized boost
pressure to accommodate all engine speed and load
conditions. An additional benefit is lower emissions.
The VGT relies on electronic feedback loops provided
by the Exhaust Back Pressure (EBP) sensor via the
Electronic Control Module (ECM).
The turbocharger assembly contains a series of
actuated vanes, a unison ring, and piston. The vanes
regulate the flow of exhaust gases across the turbine.
The only serviceable item on the turbocharger
assembly is the control valve.
Exhaust
The
exhaust
system
includes
the
following
components:
•
Exhaust valves
•
Exhaust manifold
•
Turbine side of the turbocharger
•
Exhaust piping
Exhaust gas from combustion passes around two
exhaust valves, through the exhaust manifold and is
directed through pipes to the turbocharger exhaust
inlet.
As hot expanding exhaust gases flow into
the turbocharger, they pass over the turbine wheel,
causing it to spin in direct relation with the amount
of exhaust gases being produced.
The right side
cylinders also provide a portion of their exhaust gases
to supply the exhaust gas recirculation system.
EGES235-2
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
Follow all warnings, cautions, and notes.
© 2006 International Truck and Engine Corporation
