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Monday, June 20, 2011

VGT on Diesel Engine

Variable Geometry Turbocharger (VGT), as the technology trend in current diesel engines. This technology have implemented on diesel engine that use common rail technology or on the engine that limited by engine emission.
How Turbo Work
Other name of VGT is variable turbo geometry, VVT (variable vanes turbocharger) or VNT (variable nozzle turbocharger), depend on the engine producers.

The benefit of this technology is turbine impeller or the part that pushed by exhaust gas, have changeable incline position accordance with the engine position. With the changeable impeller position, compressor that siphon the air can be adjusted by the engine force. By this technology the turbo lag symptom that often happened on non VGT or dead impeller can be avoided. Turbo lag on non VGT system happen on slow moving, because the exhaust gas can’t push or turn the impeller.

On high rotation, the pressure of waste gas more high, this can cause the turbine rotation very high (more than 100,000 rpm). To avoid this condition on the waste gas make a “wastegate”, this channel before turbine. By this system, turbine rotation can be kept on safe limit.

Work at Low Speed
Work at High Speed
VGT usually use in diesel engine, because on the gasoline engine, VGT have complex problem, waste temperature very high. On gasoline engine, waste gas temperature can reach 950 oC, while on diesel engine reach 700 o to 800 oC. Because of those problem, VGT just apply to diesel engine.