Quote:
Originally Posted by cstavaru
It is not possible for an inline-6 engine to have two twin-scroll turbochargers. It would mean separating 6 cylinder outputs into 4 exhaust paths, which is impossible.
It would not be unconcievable for me that the next M3 would have one small twin-scroll turbocharger (for lag-free operation and powerful low-end) and one large single-scroll turbocharger for top-end power. They can also employ variable geometry turbine for the large turbo, to further optimize the power band. But I am not sure that this configuration can achieve a flat torque curve from like 1200RPM, because the large turbo has no way to begin spinning at that engine speed and the small turbo would have to provide all the torque until 2000RPM which would be quite hard to achieve. But who knows...
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That's interesting about twin scrolls not being possible.
With regards to a possible variable geometry turbo, if used at all I bet it would be on the first smaller turbo. That is how BMW's sequential turbo setups work for all their diesel cars and it makes a lot of sense to allow the first turbo to have a wider torque curve to achieve the smooth torque curve that you're talking about.
But what petrol cars use variable geometry turbos besides the 911 Turbo? From what I understand they are much more expensive and BMW's electric assisted turbo concept that has been rumored to be in consideration provides similar functionality, maybe even better functionality. Their concept for the electric turbo is genius.