Quote:
Originally Posted by mapezzul
Less lag w/ n55 thanks to plumbing and twin scroll.
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Still, we must not forget that by using twin-scroll instead of twin-turbo, a degree of freedom is lost. The two gas flows are no more independent because the scrolls share the same axle (right ?). The banks of cylinders operating on the two flows must be perfectly matched, otherwise different gas flow speeds on the two separate airways could alter the engine behaviour negatively.
Also, I believe the twin-scroll turbine is quite a lot more expensive than a single-scroll. I don't know if on the N54 both turbos break at the same time usually, but if you have to replace a turbine on the N54 it will be probably much cheaper than on the N55.
I am very curious if the next M3 (which I believe will be an inline 6) will use a single twin-scroll turbo or 2 classic ones...that will be the moment where we will see if the twin-scroll technology is just for cost or for performance.