Okay, For instance many positive displacement pump systems use what is called a primer or booster pump to provide better NPSH for the pos. displacement pump. Most of the "booster" pumps are centrifical type thus a turbo (being a centrifical air pump) and a roots blower (being a positive displacement screw type pump) should compliment each other.
Now that I am done rambling... it sounds like there is alot of room to experiment with the benifits and pitfalls of a setup like this but it should pose no actual working issues... as for the intercooler idea I think that the idea of placing the inter cooler between the super charger and the intake plenum is for the same reasons you would on a single stage boost setup... it is more efficent, every time you compress a gas it's temp will go up and the best charge of air is the coolest.

Now question about the remounted turbo..... doesn't the extra length of pipe add head loss to the air flow and thus create a lag effect??... I mean that is a long way for the gas to travel and if at idle speed then jumping to WOT the exhaust gas must move all the way down the pipe..spool up the turbo and raise pressure/velocity of the gas all the way back up to the intake.... sounds like adding one problem to fix another if you ask me.

 

thats what i first thought when i saw a fear mounted turbo. up untill then all i had seen is engine bay mounted set ups and the idea of sticking a turbo "all the way down there" was odd to me. but after looking into it and thinking about it there seem to be very few problems. foor starters, i dont actualy think the runners are a great deal (like X2) the length of normal ones. and when you look at the shape of a normal equal length turbo headers they have many twists and turns in (all adding restriction) and cast manifolds are even worse. at least mounting the turbo at the back will alow the gasses to mix and become more stable. often you find that the cold side of turbo set ups also requiers complex twists and turns where as a rear mount poses far few porblems. then there is heat, and the fact that sticking the turbo(s) up front will increase the under bonnet temps, where as at the back this is a much smaller problem. some of the C5 guys have spoke about transmition temps, and i can see where they are comeing from, but with some heat shielding around the turbo, this could be minimised.

the main advantage to sticking it out the back though, is on the above application space would be really tight. and the lag of the turbo would be much less of a problem with the aid of the supercharger. so wit hthe above addvantages, and the addvantages of the S/C i think it would be the best place to put it!

thanks Chris.

 

I don't think that the frictional head loss due to bends in the system are that restrictive compared however to the increased volume of air that resides in such a long runner. It would have more of a freight train or bumper to bumper traffic like effect on the speed at which the gas accelerates. It just seems to me that a smaller volume of air would accelerate faster than a larger volume thus the larger volume would see more turbo lag.
That being said since we are examining the system such that the turbo boosts the super charger and the higher exhaust gas velocity caused by the super charger aids in spooling up the turbo (minimizing the lag) I would agree with locating it in the rear of the vehicle..but as a stand alone power adder..I say it would be more effecient to leave the turbo under the hood.

 

i agree 100%. you will get less lag if you mount any given turbo upfront. but as you said, there are other things to consider. all i was pointing out was, from what i have seen, it isn't that much of an issue. now on a 2.0ltr i could see it being a BIG problem, but then you would have more space up front so thats where you would put it! horses for corses!

thanks Chris.