Turbo + Supercharger=???

[Jon E]

I know this isnt a Buick, but....

I have a Mustang with a Kenne Bell (Autorotor) supercharger on it. If I were to take a small turbo (or a cent blower) to "precharge" the KB what would happen? If the boost out of the turbo was kept down low, like 1-2 psi, what would be the effect on the boost out of the KB? At 1psi shouldnt the boost pressure out of the KB double? What about the heat? Would it double too or would it be less?

Has any body else tried this?

 

[JDEstill]

What's the KB, isn't it a screw type compressor? Whatever, I think you can assume that it will have a given pressure ratio at a given speed, ie outlet pressure divided by inlet pressure (on an absolute scale). So, if the KB supercharger was making 8 psi boost at some rpm, with, say, 2" Hg at the inlet (to allow for air filter and MAF and such, and -1 psi = 2" Hg), then it would have a pressure ratio of (8 + 14.7) / (-1 + 14.7) = 1.657

So, if you then put 2 psi boost at the inlet, you would expect to get 1.657 * (2 + 14.7) - 14.7 = 13 psi out of the KB 'charger.

Temperature-wise, you can assume that the temperature rise across the KB unit would be the same as before, but since the inlet temperature to the KB unit would be hotter due to the turbo compressing it, the outlet would be hotter as well. The difference would be whatever temperature rise you get across the turbo.

When it's all said and done though, I'd expect it to be a complex system, and we'd just have to ask "Why?" If you go through the trouble of installing a turbo system, just run the turbo at 15 psi or whatever and ditch the supercharger. You can't use a smaller turbo just because you only want to run 2 psi boost, you still need to move the same amount of cfm that you would if running 15 psi, so nothing saved there. And you'll free up a lot of hp by not having that supercharger sucking power off your crank.

John

 

[Jon E]

Thanks John,

Thats exactally the info and formula I needed. I wasnt actually thinking of using a turbo at all but a Vortech A-trim (a small cent blower) instead. The Vortech is cheap and easy and will bolt on right in front of the KB. I hope I can pully it down so it doesnt generate too much heat while still making a little boost up top to pick up where the KB tapers off, around 4750.

I know I could make a whole lot more power with just a turbo alone but for this car I want to do somthing waaay different from anything else on the road and I think this is it. I just need to get all the bugs worked out, like the heat problem.

 

[Mikael]

I would reccommend intercooling the vortech's boost. This way, the kenne bell is compressing denser air. This is what's done for some of the older F1 cars that were making like 5-6 bar of boost.

 

[Jon E]

If I do this, what would be the best way to setup a bypass? Should I just keep the individual bypasses on each blower, plumb them togther or just use a single blow off valve after the KB?