Originally posted by importsyn
You're missing the point, on a twin turbo set up there isn't one turbo to handle power for half your cylinders and another turbo to handle the other half.There's one smaller turbo to handle bottom end power(ie)quicker spool up,usable torque,etc.),the second turbo kicks in at a higher RPM (there's a crossover point,almost like VTEC) to handle top end power.
I'm talking about a PARALLEL twin turbo setup, what you are talking about is a SEQUENTIAL twin turbo setup, there are 2 kinds of twin setups. If you have one turbo being run by 2 cylinders and another turbo being run by the other 2 cylinders, than that is a PARALLEL turbo setup. Because the 2 turbos would be working at almost the same time (parallel to one another).
That's all there is to twin turbo cars, look at factory specs on 300zx's,RX-7's and Supra's.They all have small primary turbos and large secondary turbos.I hope this clarifies any confusion.
I know that those cars come with stock SEQUENTIAL turbos, but it is not uncommon for owners of those cars to switch the turbos to PARALLEL operation. Parallel operation is when both turbos spool at the same time, instead of the smaller one at low RPMs and the larger one at high RPMs.
If you were to want to TT a 4 cylinder a sequential would be a poor choice. I think that only NA cars that have a lot of exhaust flow and a lot of room in the engine bay would benifit from a sequential setup. For example the S2000, if there was enough room in the engine bay the car would handle a sequential setup pretty well, since it flows the same amount of air as an FD with no turbos (no boost). However sequential turbo setups are more complex than parallels, which is a one of the reasons that most MKIV and FD guys go parallel.
EDIT: also, FYI the 300ZX TT has a stock PARALLEL system....it IS NOT a sequential system.