SSANGYONG Korando 2012 Manual page 220

4. OPERATING PRINCIPLES
The E-VGT is designed to get more improved engine power in all ranges by controlling the
turbine as follows:
1) How it Works at Low Speed
Normal turbocharger cannot get the turbo effect because the amount of exhaust gas is not
enough and the flow speed is slow in a low speed zone, but VGT allows the flow passage of
exhaust to narrow, resulting in increasing the flow speed of exhaust gas and running the turbine
quickly and powerfully. Therefore, as VGT can intake more air than normal turbocharger, it can
give the benefit of the increased output even in a low speed zone.
Control
Turbocharger driving
range
mechanism
At low
speed
※ Basic principle at low speed
At low speed, it utilizes the principle of venturi.
For example, when air flows through the
venturi tube, the flow speed is faster and the
pressure is lower at the point "A". In this case,
if the inner diameter of venturi is more
narrowed, the flow speed is so much faster
(refer to the equation).
Turbocharger lag
The turbocharger is at idle speed when there is no load or it is in the normal driving condition.
During this period, the amount of exhaust gas passing through the turbine is not enough to turn
the compressor wheel (impeller) fast. Therefore, the intake air is not compressed as needed.
Because of this, it takes time for turbocharger to supply the additional power after the
accelerator pedal is depressed. This is called "turbocharger lag".
Control method
The flow rate is
increased as the
exhaust gas
Narrows the flow
passes the narrow
passage for the
passage
exhaust gas by
→ Increased
folding the vanes
turbine & impeller
speed, Increased
compressive force
0000-00
Improved
Effect
performance
Improved
low speed
torque
06-21