Oh hear we go again, turbo talk!! Turbos are a compromise. The housings on the compressor and turbine sections are both closely matched to the engine for each application. The turbo must be small enough to spool up quickly yet large enough to provide enough flow and boost at high rpm. This results in a compromise as a smaller turbine section would provide more boost at lower rpms but not flow at high rpm and a large section would flow like gangbusters and make plenty of boost but the lag would be huge waiting for the thing to spool up. Various schemes have been tried. Mazda tried a twin-sequential turbo system on their RX7. A small turbo worked alongside a large turbo with a whole pile of electronic wizardry to make plenty of boost all over the rpm range. There are also VNT turbos from Garret that have a "vane" that directs the gasses. It directs more exhaust gas against the turbine at lower rpms to spool up quickly and then opens up as rpm/boost rises to flow better. Finally there are modern computer controlled engines that seamlessly blend the power curve so that you really don't feel the turbo lag. VW TDI's are a good example of this. Our "classic" MB's are based on older technology and ideas so yes there is turbo lag but its really quite mild compared to some other turbo systems. At lower rpms your turbo simply isn't spinning fast enough yet to provide significant boost. RT

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