Hi guys

let me start by saying I have a used Vortech kit installed...runs great w/ good numbers but I do have the BOV "whistle of death", where my BOV send out this ridiculously loud tea-kettle type whistle at idle due to a not properly sealing BOV...other that that runs great....

So I've ordered a new BOV since it's basically terminal for your BOV when you get the whistle but since I have to wait to get it, I decided to try some different things to minimize the whistle...I found out that (as others vortech owners w/ bad BOV's have discovered...) if you disrupt the airflow out of the BOV it will take away the noise....in my case covering half of the BOV output seemed to take away the noise....

So I decided as a temporary mod to duct tape half the BOV opening and use one of those clamps that hold the sleeves/reducers down to keep the tape from flying off at least until my BOV shows up...

My question is: is it bad to do this for now? Will there be any problems that may occur for covering half the BOV until my new BOV arrives?

 

I would not cover the the exit of you BOV as this may not allow all the pressure to release when you come off the throttle. This may cause back pressure on the SC and could cause bearing problems.

 

Isn't the bypass valve supposed to be completely open at idle?

 

yep.

 

the vortech uses a bypass valve, not a blow off valve....

I also agree that this does not sound like a great solution.

 

buy a small air filter and add some foam to the inside and install it over the Bov. works great and knocks out about 75% of the sound.

 

Interesting, but I wouldn't recommend it. I would personally just leave it the hell alone and stay out of boost until the new one arrives.

 

It's not to fix a bad bov, it's to muffle the sound only.........I recommend it. 30,000+ mile with it.

Just because a bov make a whistle, does not mean it's bad. sound waves to strange things.

 

How'd you get the filter past the sway bar, OldMan?

 

I put it on 4 years ago, it fits. The filter is flexable.

 

Are you sure you don't have the adjustment bolt too tight, causing the BPV to not be fully open at idle?

 

Traitor! haha just kiddin man, hope you are liking the STS, I'm contemplating a Powerlab this winter lol. Ok back to the OP's topic. Johnny does make a good point though, 6-8 threads should be showing.

 

I think I only have 3~4 threads showing....it came that way when i bought it used....

and you're talking about the adjustment screw on top of the BPV right?...you don't adjust the inlet where the vacumm hose goes, right?

 

+1 to the filter idea. I had one on my bov of my turbo setup to mellow out airflow entering at idle. I have since corrected that issue and am not running the filter. But it is still a decent idea for someone who is concerned about getting dirt into the system via BOV. That is as long as you are getting sufficent pressure release with the filter.

 

Your bolt is two far in then. The further in the bolt it the more preload the spring inside has counteracting the vacuum trying to open the valve. What you hear is the valve being open just enough to let air through at idle but it creates a whistle due to the high velocity caused from the small gap.

If you loosen the bolt a bit so the preload is less the whistle will go away at idle. However, you may get it at a slighlty higher rpm. Here is a video I got of my car on the dyno where I got some whistling while running at low rpm's:
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^^So you're saying adjust the bolt pointed out below to maybe 6 threads showing?

Will that affect how soon I get my boost rpm wise?

 

the screw determines how much vacuum you need to see before the BPV opens.

ie: tighter, more sensitive as and smaller lift in throttle will cause it to dump more boost,
but less chance of compressor surge

ie: looser, less sensitive, so it wont dump boost as fast between shifts, could have compressor surge

 

No.

What I am saying is that the screw adjust the condition under which the bypass valve opens.

Your instance is not a bad BPV. Your screw is too far in, but just far enough out to make it whistle.

Lets say you have the screw in enough so that the preload on the spring would cancel out 20-inHg of vacuum. If your manifold vacuum is say 24-inHg, that means you have 4-inHg of active vacuum on the valve. However, due to the nature of a spring and the operation of a BPV, that 4-inHg of vacuum will pull upward (moving the valve open) the distance required to preload the spring to a pressure that cancels out the 4-inHg of active vacuum.

At this point, with a steady state of vacuum, the valve will float at the height required equalize all forces (i.e. pipe pressure against the valve, vacuum signal, spring preload). When you tighten or loosen the screw, you indirectly adjust that height which the valve has to go to equalize forces between the vacuum and the spring.

The further you tighten the screw, the less the valve has to move to equalize these forces. So if you tighten the screw in enough, the spring pressure will exceed the opposing force of the vacuum. At this point, the valve will not open up like it should during idle and the opposing equal force against the over-preloading spring will be the cast aluminum body that stops the valve.

Soooooo..... it sounds like you have the screw a bit too far in and what is happening is that when the forces inside the valve all equal out, the valve is only a short distance off the seat. This means you are trying to shove a lot of air through a smaller opening, therefore increasing the velocity of the air and getting whistling.

This is the same concept behind why people state that the more high pitched a blowoff valve is, generally the more restrictive it is. Blowoffs get higher pitched when you restrict them in a fashion that increases velocity while still maintaining a direct vector.

I hope that this over explained post helps.