Procharger bypass/blowoff valve recommendations?

[IUP99snake]

Im looking to replace the blowoff valve I'm currently running with my procharger setup. I have a blow thru system and the valve is located before the MAF, so it doesn't matter if I vent it to the atmosphere or not.

The problem I'm having with my current blowoff valve, which is a piston and spring style, is that it is not opening at idle, and only seems to vent air when the pressure forces it open, causing it to flutter. I also worry that it is not holding in all the boost. I'm also worrying that it might have a vacuum leak on the diaphragm side, and we all know the pain in the ass vacuum leaks can be.

When I had the original procharger bypass valve, which was a butterfly style, it would open up all the way at idle, and of course, open up properly when I let off the throttle. The only thing that sucked about it was that I knew it leaked boost because the butterfly valve didn't make a good seal against the Venturi. You could see light through it. At least it would open and close properly, and while it didn't make a perfect seal, I knew at least it wasn't bleeding off boost once it reached a certain PSI.

First off, is there any difference between a blowoff/bypass valve designed for a turbo, and one designed for a centri? They should both open up fully under vacuum conditions present during idle and when you let off the throttle. The only thing I can think of is that the piston style valves have springs you can replace or other forms of adjustment. I don't see why there should be any adjustment.. They should be open during vacuum and closed during boost pressure.

I'm thinking of just going back to the stock procharger bypass valve for the sake of simplicity.

Or I was thinking of something like this:
TURBOXS 25MM BOSCH BYPASS VALVE REPLACEMENT RBV-25
http://bit.ly/xuIQjT

I dont feel like welding on a new flange, so I have to stick to a valve that has a hose mount, like the stock procharger valve or the one I posted above.

What does everyone think? Can anyone recommend a better valve for around 100 bucks? What are you all running?

Or is anyone looking to sell a stock procharger valve or something better for a reasonable amount?

Homer

 

[Mr. Anderson]

the only thing I would say with a BOV like a TiAL blow off valve or any aftermarket BOV is to get the correct spring for it. it is usually a 2-3 pound spring and it is specific to a Blower (especially a Centri type). if you get a regular BOV set for a turbo the vacuum setting for the BOV to actuate is set to high (depending on their set up they set them to the average vacuum of the engine at idle/cruising (12-24 lbs of vacuum depending on the engine) and can cause unwanted pressure on the head unit, and over time will cause premature failure on on either the bearings or the pressure seal.

 

[IUP99snake]

Thanks for the advice. I think a good vacuum amount for it to open would be anything higher than 5 inches/hg. That'll keep it open at idle (20 inches) and also during freeway cruising (10 inches).

I'm gonna take mine off and test it with a vacuum pump to see when it opens up. The problem could be the vacuum source I'm using. Right now it's T'd near the boost gauge, which is also T'd off the vacuum hard lines at the back of the intake. I should probably use a dedicated vacuum source for this.

I think what I'm going to do is take the boost gauge and BOV lines from the other vacuum hoses and use a dedicated source for just the two of them. I'll probably run a vacuum line straight to the BOV and then T off of it near the BOV and run a line back for the boost gauge. That way I get an accurate reading of what exactly the BOV is seeing.

I have some idle surge/hanging issues, and I've always blamed it on my BBK throttle body, but I think it might be caused by the BOV not opening at idle. There's a lot of air moving through, even at idle.. I remember my stock procharger valve used to be like a leaf blower at idle. With nowhere else for that air to go, it could be causing the idle problem. A good way to check would be for me to just pull off the BOV, plug the line, and do a test drive with it open and see how it behaves.

 

[Mr. Anderson]

yeah, most BOV manufacturers recommend a single source straight from the manifold for the BOV and not off a T'ed line. definately check the valve with vacuum gauge to make sure it's working correctly first and see when the valve actually cracks open.

 

[Chances50]

I have a Tial Q on mine, i was running the 3psi spring but it was annoying me so i ordered a 6psi just to test it and man what a difference its twice as quiet and no blower fluttler/surge. also had a small vac line and upped it to a larger 7/32 i think and it seemed to help also.

also make sure you have a dedicated vac line from the intake.

also for what your running the current 25mm BOV isnt big eough i had a greddy knock off and it was to small went to the tial Q 50mm and problems solved. they are around $230.