A twincharger refers to a compound forced induction system used on some internal combustion engines. It is a combination of an exhaust-driven turbocharger and a mechanically driven supercharger, each mitigating the weaknesses of the other. Twincharging does not refer to a twin-turbo arrangement, but to a setup where two different types of compressors are used (instead of only turbochargers). Overview and advantages A mechanically driven supercharger offers exceptional response and low-rpm performance, as it does not rely on pressurization of the exhaust manifold (assuming that it is a positive-displacement design, such as a Roots-type or twin-screw, as opposed to a centrifugal supercharger, which does not provide substantial boost in the lower rpm range), but is less efficient than a turbocharger due to increased parasitic load. A turbocharger sized to move a large volume of air tends to respond slowly to throttle input, while a smaller, more responsive turbocharger may fail to deliver sufficient boost pressure through an engine's upper rpm range. The unacceptable lag time endemic to a large turbocharger is effectively neutralized when combined with a supercharger, which tends to generate substantial boost pressure much faster in response to throttle input, the end result being a lag-free power band with high torque at lower engine speeds and increased power at the upper end. Twincharging is therefore desirable for small-displacement motors (such as VW's 1.4TSI), especially those with a large operating rpm range, since they can take advantage of an artificially broad torque band over a large speed range. Types A twincharging system combines a supercharger and turbocharger in a complementary arrangement, with the intent of one compressor's advantage compensating for the other's disadvantage. There are two common types of twincharger systems: series and parallel. Series The series arrangement, the more common arrangement of twinchargers, is set up such that one compressor's output feeds the inlet of another. A supercharger is connected to a medium- to large-sized turbocharger. The supercharger provides near-instant manifold pressure (eliminating turbo lag, which would otherwise result when the turbocharger is not up to its operating speed). Once the turbocharger has reached operating speed, the supercharger can either continue compounding the pressurized air to the turbocharger inlet (yielding elevated intake pressures), or it can be bypassed and/or mechanically decoupled from the drivetrain via an electromagnetic clutch and bypass valve, increasing induction efficiency. Other series configurations exist where no bypass system is employed and both compressors are