Dual turbochargers, rather than a supercharger/turbocharger combination, create forced induction and feed air to the TDI 4.2 350s. Turbo whine and a supercharger’s whistle are sounds those of us who run diesel-powered boats have become inured to, the price paid for delivering more air to the cylinders, which, in turn, allow more fuel to be burned, and so increase power. In simplest terms, both superchargers and turbochargers are air pumps, or compressors. The difference lies in how they are driven. Superchargers are mechanically driven by belts or gears, like an alternator. A turbo uses the stream of engine exhaust gas to spin turbines.