I would think the turbo would then have a hard time trying to suck thru the blower, and you wouldn't make much more than the blower by itself.

 

Well, I haven't been messing with it too much latley, but I did try a bigger superchager pulley. I put a 3.6 on it which makes about 4 psi until the turbo spools. I put a new boost controller on it, and have it set to 10 psi, so now I have 2 boost gauges so I can see the manifold boost and the turbo only boost.

From a standing stomp, it jumps up to the 4 psi the blower makes and then spools the turbo pretty fast and maintains about 5-6 psi over the turbo only boost till about 10psi and 4000 rpm, then the boost just starts climbing like a procharger. I've seen 20psi 3 or 4 times! .

I know it still need more waste gate, but it just doesn't feel like 15-18 psi should on this motor and the money tree has pretty much dried up on this science project so the Blower is coming off in the next couple weeks (and is for sale ) and am gonna go back to turbo only with this S475 and a quick spool valve to get it spooled. One day, when I have a little more dedicated play truck, I will most likely revisit this experiment.

 

I think getting a quick dyno pull before you take her apart would at least give you some info that you can mull over when you visit this later on. I'd also be interested in seeing what it looks like.

 

That would involve a "quick" 2 1/2 hour drive to the nearest dyno,

And I can't make a full pull with out having to lift from over boosting.

 

Damn, that sucks man. I appreciate you pioneering this for us though and doing a lot of the leg work in order to make something like this work.

You said 20psi doesn't feel like 15-18psi should on that motor. Are you saying that with turbo only, 15-18psi pulled harder? Not down low though right?

 

I think he was saying that he didn't want to blow the motor up from over-boosting

 

Sucks you're taking it off. I would have liked to have seen dyno numbers

 

How's about a way to control the bypass valve on the TVS with a electronic boost controller, as the Manifold pressure is what is causing the overboost. If you could modulate the bypass valve at vacuum / low throttle angle like stock, then allow it to operate closed like normal up to a predetermined manifold pressure, that should control you over-boost issue. Granted, I know that valve is there to reduce pumping losses in steady state low throttle conditions, it might just work. It would essentially bleed off the boost generated by the TVS back into the TB manifold.

 

Good choice. you might miss the low end instant torque, but you will make more power "Controllable" boost with just the turb.... Incase you didnt know...lol

 

Ya, it's making PLENTY of boost, just doesn't "feel" like its making the power pr/pound of boost it should. Does that make since? I might go ahead and put the extra 38mm gate I have in the crossover to see if that fixes the boost creep and hit the track once just for giggles, but I think results will be less then stellar.

As far as going turbo only, I have a devise similar to this that my machinist is building me right now that will make this big 1.36 a/r turbo spool more like it has a .68 a/r but it will open up and have more flow once the turbo gets up to speed. Should really help the spool time. A couple of guys on LS1tech are running them and seem to LOVE them on these big, divided housing turbos. Seem to cut spool times by about 1/3.