SSANGYONG Korando 2012 Manual page 216

1. SYSTEM DESCRIPTION OF E-VGT
(Electric-Variable Geometry Turbine)
A turbocharger is a centrifugal compressor powered by a high speed turbine that is driven by an
engine's exhaust gases. Its benefit lies with the compressor increasing the mass of air entering
the engine (forced induction), thereby resulting in greater performance (for either, or both, power
and efficiency). As the turbine, at exhaust end, is rotated by exhaust gas pressure the impeller, at
intake end, gets rotated to send air around center of the impeller, being circumferentially
accelerated by the centrifugal force, into the diffuser. The air, which has been introduced to the
diffuser having a passage with big surface, transforms its speed energy into the pressure energy
while being supplied to the cylinder improving the volume efficiency. Also, the exhaust efficiency
improves as the exhaust turbine rotates. The turbocharger is often referred to as the exhaust
turbine turbocharger.
Diffuser: With the meaning of spreading out it is a device that transforms fluid's speed energy
into the pressure energy by enlarging the fluid's passage to slow down the flow.
The E-VGT system installed to the D20DTF engine variably controls the passages of the turbine
housing to regulate the flow rate of the exhaust gas. The actuator of E-VGT is a DC motor
actuator (E-Actuator) which controls more quickly and precisely than the previous vacuum type
actuator.
The engine ECU controls the E-Actuator electronically as follows:
- At low speed: Narrows the flow passage for the exhaust gas, resulting in increasing the flow
speed of the exhaust gas and running the turbine quickly and powerfully.
- At high speed: Expands the flow passage for the exhaust gas, resulting in increasing the
mass flow of the exhaust gas and running the turbine more powerfully.
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