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Volkswagen EA111 1.4 engine coolant pump is work together with supercharger.The construction of Twincharger is quite simple. It has a Roots supercharger and a turbocharger connected in series. The supercharger can be bypassed through an alternative path, or disengaged completely by an electromagnetic clutch.

At low rev, the supercharger provides most of the boost pressure. The pressure it built up also helps spooling up the turbocharger so that the latter can run into operating range more quickly.

At 1500 rpm, both chargers contribute about the same boost pressure, with a total of 2.5 bar. (Had the turbocharger worked alone, it could provide only 1.3 bar at the same rev)

Then the turbocharger – which is optimized for high-rev power – started taking the lead. The higher the rev, the less efficient the Roots-type supercharger becomes. Therefore a by-pass valve depressurizes the supercharger gradually.

By 3500 rpm, the turbocharger contributes all the boost pressure, thus the supercharger is disconnected by the electromagnetic clutch to save energy.

The Twincharger is quite an achievement. It delivers excellent power and tractability yet the package is surprisingly compact. The only disadvantage is high cost. Predictably, it costs significantly more than a turbocharging system. As modern turbocharging has improved low-end response a lot, the significance of Twincharger is inevitably reduced. This prevents it from further penetration into the mass market.