The next-generation Porsche 911 Turbo will offer Variable Turbine Geometry. VTG is a system that continuously adjusts the angle of the compressor's turbine blades. VTG systems have been used in diesel engines since the early 1990s, but the Porsche application is the first for a turbocharged gas engine.
VTG can provide significant improvements in engine flexibility and responsiveness, particularly at low engine speeds.
Until now, VTG's advantages have been limited to diesel applications where the exhaust gas temperatures are relatively low, compared with much higher temperatures in turbocharged gasoline engines. Working with Borg Warner Turbo Systems, Porsche has overcome the temperature limitation through the use of temperature-resistant materials derived from aerospace technology.
The unique feature of the VTG system are the variable turbine blades, which articulate to optimize the flow of exhaust gas onto the turbocharger's turbine wheel. The blade angle is controlled by the engine management system. Turbochargers can be designed to operate best at high engine speeds, but performance at low speeds is compromised. The same can be said about designing for low speeds, while compromising high-speed operation. The big attraction of VTG is to combine the benefits of a small and large turbocharger in one unit.
Another significant side benefit is a large torque plateau that can be maintained throughout a much wider speed range.
It's due in September 2006.
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