VOLKSWAGEN has a system that can make a car with a little engine take off like a jet plane. It's called twincharging and involves the use of a supercharger and a turbocharger.

This TSI technology has been used on the Golf hatchback and is now being applied to the Jetta sedan, a booted version of the Golf. The Jetta may not have many redeeming aesthetic qualities, but with its 1.4 TSI, this plain Jane is transformed into mad Max.

Floor the accelerator and the front-wheel-drive Jetta TSI zooms off like it has rocket boosters.

The supercharger provides the small 1.4-litre engine with low speed oomph below 2,000 rpm before the turbocharger - which is prone to turbo lag below that engine speed - takes over.

The result is all the power you need plus the seemingly contradictory ability to achieve good fuel economy. Under a combination of urban and highway driving, the Jetta TSI can turn in consumption of 7.3 litres per 100 km, or 13.7 km per litre. This is 8 per cent better than a Jetta with a two-litre turbocharged engine.

VW engineers were able to reach this higher level of fuel efficiency because when the load is low, neither charger is in operation. Also, they say that the 1,400cc engine itself has a low-enough displacement to ensure that it stays economical even with twincharging.

The only drawback is despite the supercharger working at low engine speeds, the Jetta TSI still exhibits some lag before the power comes in with a bang. This on/off effect needs getting used to but the brilliant dual clutch direct shift gearbox helps to make it a smoother drive.

The Jetta TSI also costs more than a normally aspirated Jetta 1.6 automatic - almost $13,000 extra. Sadly, power never comes cheap.

This article was first published in The Business Times on Apr 12, 2008.