Super Turbo - How does it work?

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I have to admit there is a gap in my knowledge of forced induction systems, and the March Super Turbo is right in the middle of it. In the States, running two types of compressors is usually called Twincharging, and for a while HKS sold a kit that turned a Supercharged Toyota MR2 into a Twincharger. The thing is, these cars are rarely smooth. The transition from s/c to turbo is never terribly subtle, and does not give the most holy "linear torque curve" that is the whole point of twincharging. I pretty much gave up on the idea of twincharging after seeing one of the Toyota's myself, until I heard about the March Super Turbo.

I know from reading little tidbits that it is genuinely twincharged and has very good power delivery and, best of all, a smooth transition between compressors. So, how does Nissan accomplish this? I'd like as much detail as you can muster on the system. This is not idle curiosity; such a setup may someday appear on my car. I'd love to be able to upgrade to a full T04E turbo, but it's not going to happen without something to bring up the bottom end. Any help on this is much appreciated.

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