Volkswagens' technology labs have come up with another innovation for their VW Golf series: A combination of a supercharger and turbocharger. The SuperTurbo is aimed to be introduced on the 2006-model of the Golf.
A Supercharger is driven by the engine, and allows a car to take in more air through forced induction. This means that the engine becomes more efficient. While the Supercharger itself could take as much as half of the engine's output, is is generally accepted that superchargers boost the performance of an engine by up to 100% - A nice trade-off then.
Turbochargers are generally seen to be more effective, as they work by adding a turbine to the exhaust system of the car. In non-turbo cars, the exhaust gasses are basically a lot of lost power (temperature, pressure, etc), which needs be quieted through the exhaust system, and then gets released. With a turbocharger, the exhaust gas pressure is exploited, by connecting the driving turbine to a pump that forces air into the engine. The downside with a turbocharger, of course, is that it only works when the engine is creating excess pressure, which it only does properly when the engine is running at higher revs.
In the new combination system, Volkswagen does something clever: Once the turbo is providing boost, the supercharger’s clutch is disengaged and it is closed off from the induction system, allowing the turbo to take over completely
Volkswagen claims that their combination allows a 1.4 litre petrol engine to develop 170 horsepower and 199 lb/ft of torque. In comparison, the current VW 2.0 litre engine delivers roughly 150 bhp and 150 lb/ft of torque.
After the 1.4 litre engine has been tested, it is expected that VW will roll out 1.6 and 2.0 litre engines - all with an approximate 20% better fuel economy and power than their predecessors.
Whilst the concept of a combination of a supercharger and a turbocharger is not new (it is especially used in propellor-driven aeroplanes, and was used as early as the second world war), this is one of the first times that a mainstream automotive manufacturer has introduced the system in a high-volume production car.