Turbochargers used on automotive engines are well known for their ability to increase engine output. By forcing more air into the engine via the turbocharger’s compressor, more fuel can be injected into the engine thus increasing its output. Using a turbocharger also makes an engine eco-friendlier.
The turbocharger improves engine efficiency by using the energy contained in the exhaust gasses in the form of pressurized gas and heat to drive the compressor. A second ecological advantage is that it enables the use of a smaller and more efficient engine delivering the same level of performance, which makes for a lighter vehicle and thus further reduces fuel consumption.
This system, however, has one well known disadvantage: turbo lag during acceleration. Turbo lag is the delay between the moment you hit the accelerator and the engine’s response. The turbocharger’s acceleration is delayed by the time needed for the turbine and compressor to reach operating speed. A smaller turbocharger has reduced lag, but it reaches its top speed faster, limiting the engine range where the turbocharger is useful.
Porsche has developed a variable geometry turbocharger. The system uses mobile vanes located in the turbine inlet; as the angle of the vanes changes, the speed of the turbine varies. The turbocharger can thus pick up speed faster during acceleration and limit its rotational velocity at higher engine speeds.
This technology reduces turbo lag while ensuring high performance on a wider engine rpm range.
Variable geometry turbochargers maintain a car’s high performance level by allowing the use of a smaller, eco-friendlier engine, without the drawbacks usually associated with turbo technology.
photo:Philippe Champoux
The turbocharger improves engine efficiency by using the energy contained in the exhaust gasses in the form of pressurized gas and heat to drive the compressor. A second ecological advantage is that it enables the use of a smaller and more efficient engine delivering the same level of performance, which makes for a lighter vehicle and thus further reduces fuel consumption.
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This system, however, has one well known disadvantage: turbo lag during acceleration. Turbo lag is the delay between the moment you hit the accelerator and the engine’s response. The turbocharger’s acceleration is delayed by the time needed for the turbine and compressor to reach operating speed. A smaller turbocharger has reduced lag, but it reaches its top speed faster, limiting the engine range where the turbocharger is useful.
Porsche has developed a variable geometry turbocharger. The system uses mobile vanes located in the turbine inlet; as the angle of the vanes changes, the speed of the turbine varies. The turbocharger can thus pick up speed faster during acceleration and limit its rotational velocity at higher engine speeds.
This technology reduces turbo lag while ensuring high performance on a wider engine rpm range.
Variable geometry turbochargers maintain a car’s high performance level by allowing the use of a smaller, eco-friendlier engine, without the drawbacks usually associated with turbo technology.
photo:Philippe Champoux