vanillagorilla

iTrader: (1)

This post is a little lengthy, and math is involved, see cliff's notes at bottom.


There's the advantage of making big boost numbers on a little engine like parish said, but more importantly doing it quickly. The way the compound boost numbers work out is like this:

Say you have a blower that makes 6psig, and turbo that makes 6psig. Everybody thinks that you take 6psig X 6psig and get 36psig, or 6psig + 6psig to get 12psig. Thumbing through some of my books revieled that you have to use good 'ol pressure ratios and you have to account for absolute (ambient, atmospheric) pressure psia.


Ok, sea level is 14.7psia, and we're making 6psig. We now have a PR of roughly 1.4. You have a PR of 1.4 from the blower and a PR of 1.4 from the turbo, leaving you with a PR of 1.4 X 1.4= 1.96. 1.96 X 14.7psia= 28.8psia. To get boost you have to subtract the atmospheric pressure, 28.8-14.7=14.1psig. So you have only 14psi of boost.

You could easily get that with a turbo or a SC by itself with minimal side effects of either. I think to really make this setup shine, it needs to be at high boost levels. Otherwise there's no point but to say you have both. If you want big power with a small engine (that can take it) huge boost numbers can be had without much lag.

Cliff's notes:
Compounding boost doesn't mean 6psi + 6psi or 6psi X 6psi. It means you have to use pressure ratios (math). See chart below, and notice how quickly boost levels rise to limits of gasoline.

KySilverado

iTrader: (7)

The advantage to me is cost. Sure if I had the money I'd go out and buy the latest greatest equipment (TVS). Bolt it up and be done with it. Or for 1/2 to 1/3 the cost, being I already own the SC side, pick up a used STS system and have all the boost I could ever use. Put the little 112 back down to an RPM that its more efficient at 5-6psi, couple that with the STS at 5-6 psi that its happy at and rock the new found cheap power. Course all this hinges on being able to make it work but hey I'm sure to learn some things along the way.

zippy

Not sure of the spec's on the car, but I'd still assume that the turbo's would spool considerably quicker than did in the test. If you're putting down 1000RWHP out of a 4.6L it's likely an automatic with a transbrake and a 2 step. Even if it's a manual you'll still have a 2 step and be launching at 6k or so using the 2 step to build the boost quicker at launch. Even on a small motor like that if you could launch at 10psi it wouldn't take long to go from 10psi to 22psi. As for just adding an STS kit to your Radix, why not just take the Radix off and run the STS only. Wilde has so far ran quicker than all the Radix trucks that I know of leaving nitrous out of the equation. I believe the quickest Radix'd extended cab 4x4 with a 4L80E is a 12.1 or so. About .7 off of his best time. I'm not supporting the STS crew, but to add a unit onto another when the single unit can make the power without the other just seems excessive.

ZO6Ted

I agree that the sts should be considerably faster when apples to apples on a higher boost appication. But I still think I missed the instant response of the charger when off boost by being turbo only. I could see how it would make for a more powerful AND instantly responsive street ride. And then there is the money factor too.

KySilverado

iTrader: (7)

^^^ Exactly, If it were about ET's alone.... I know I wouldn't like a turbo only ride. Best of both worlds. Strong bottom and top end is the allure of the setup I have in mind.