

| Subject: | Re: yet another engine choice - VW "twincharger" |
| From: | Jim Felder |
| Date: | Wed, 28 Sep 2005 07:58:29 -0500 |
>>> >>> > > Yep... and they don't even know what a supercharger is. A > supercharger AND a turbo? A turbo IS IS IS a supercharger! > A supercharger is geared to the engine's rotating parts, like a permanently mounted fan. They are notoriously hard on engines, for which reason VW is probably using a small one and since the drive is direct, there's no lag. Turbocharging is a "softer" way to gain power by increasing boost. It's a little more complicated than a supercharger, which is a simple blower belted to and engine shaft. Turbocharging uses the flow of exhaust gas, not the engine's rotation, to turn a fan on whose shaft is another fan in the intake gas flow, so that when engine RPM is increased, exhaust flow is increased, and therefore intake flow is increased and fuel/air density in the head is increase for increase power. Turbocharging is easier on engines but has a lag as the turbo spools up to speed. Sounds like VW is using a small supercharger--too small to harm the engine but large enough to provide low-RPM boost--to provide power in the sub-turbo operating range, then a larger turbo takes over when the driver's foot demands it. Jim
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