qwiketz

Hi guys. Since the lt section doesn't have section for power adders, I thought this might be where I'd get the best info.

Concerning boost loss, I have a 383 vortech ysi setup and am only seeing about 14-15lbs of boost. I am using a 7.35" crank, 2.75" blower and have only spun it up to 5000-5200 so far, but boost isn't climbing like it should. Belt wrap is excellent around the blower pulley with just under 270* or so of wrap. I realize that I'm not spinning it hard but I still think I should be getting more boost considering I'm using a small cam (hot cam).

My question is, if there is more pressure in the discharge tube than in the manifold, how big of a differential can there be before the procharger red bypass valve gets forced open? I'm running a dual 58mm throttle body so there is a restriction between the manifold and the discharge tube.

Are there any newer parts that can help fix this if it truly may be a problem? Other than that, I'm going to be tossing in fresh valve springs; the ones I have on the car are old and probably have gotten weak which I heard may also cause some boost loss and valvetrain float.

Any suggestions, ideas or even speculation is appreciated.

asubennett

iTrader: (6)

Perform a boost leak test. It will let you know where your pressure loss is originating from.

qwiketz

What's involved with that? Should I be able to find a how to video on YouTube? Makes sense; just need a push in the right general direction to research.

Thanks!

asubennett

iTrader: (6)

http://www.siliconeintakes.com/intak...ster-p-49.html

Pop off your charge pipe. Hook this guy up. Add 10lbs of air to it and listen. Up to 15lbs and listen. 20 lbs and listen etc...

At around 30lbs you can stop. If it's not leaking there I doubt your running more pressure than that.

Wherever air is escaping you have a boost leak. Fix it. :-)

Realcanuk

With that combo of pulleys, and at 5000-5200 rpm, 15 lbs doesn't sound wrong. The blower is only spinning around 47000 rpm, far from its peak.

forcd ind

iTrader: (7)

Curious, with the boost tester, I guess you need to pull all your rockers to seal the engine up?

stevieturbo

You dont say what belt width, setup, tensioner type etc ? Those are some very very small pulleys, so wrap or not a 2.75" pulley really doesnt offer a lot of grip.

Whether there is more pressure in the discharge tube really depends ho restrictive your plumbing and intercooler is. There could be none, or loads.

But your problem will be blower drive related, or simply that you're nowhere near spinning it hard enough. Although I'd think that with such low blower speeds, 14-15psi in the intake at only 5000rpm is a lot of boost !