Superchargers
Supercharging is a popular, but often misunderstood, means of forced induction. Rob Marshall looks at what a DIYER can and cannot do, as well as the upgrading opportunities.
One way of enhancing engine power and increasing efficiency is to blow air into the cylinders under positive pressure, instead of relying on the engine to suck it in. If desired, more fuel can be injected to take advantage of the extra oxygen. The practice of forcing air into the engine is known as supercharging and the turbocharger is the most common method employed by car manufacturers. Instead of using waste exhaust gas flow, superchargers differ from turbochargers in that their compressors are powered mechanically, usually by the crankshaft, most commonly, via a serpentine belt.
However, you should think of turbos and superchargers not as alternatives but as means of offering different kinds of forced induction. While large-engined Jaguars, Land Rovers, Range Rovers, BMWS, Mercedes-benzes, various MINIS and Lotus cars tend to be the most productionised supercharged examples in the UK, certain high-performance vehicles offer a combination of both technologies. Although Lancia pioneered the idea in production, the most recent and popular example of this is Volkswagen Group’s Twincharger 1.4-litre TSI motor, fitted to a variety of its performance models until only recently, which employs a supercharger for lag-free low-engine speed torque output and a turbocharger for higher engine revolutions. High production costs are one reason why this unit has been dropped but the concept has not been abandoned. Volvo, for example, has replaced its renowned five- and sixcylinder performance units with smallercapacity, four-cylinder twin-charged units for its latest T6-badged models.