OK, as i'm sat here bored, how do the sequential turbo's work on somthing like an RX7? I havn't really read much about it, but isn't there one small turbo for quick response and one big turbo for the top end power? do theese feed through each other or do they both feed the inlet manifold seperatly, and what is the limiting factor of ultimate power? is it the size of the small turbo or can you just have the small turbo bypassed once its up and running so the big one can flow enough air to make decent power?

Say on somthing like a cossie YB , whats stopping you having a T25 and a T4 on the same engine? I know space would be an issue but would there be enough gaslow to drive both turbines? I was thinking perhaps that you could use external wastegates and use the air from the small turbo wastegate to feed back into the large turbos turbine?