Ok when I build low boost or low vacuum my Greddy Type-R BOV flutters... But when I build 7-10psi it becomes the same "whoosh" sound that it used to be. It just started doing it about a week ago. I've been thinking that it might be a vacuum leak but I can't find a leak at all. It's adjustable so I'm thinking someone may have fucked with it at a car show or something.

If I loosen it will it stop fluttering?

And what exactly does loosening and tightening the spring do? Is there a downside to too loose or too tight or is it just for the sound?

 

Are you sure it isn't compressor surge?

 

Loosening and tightening the spring is probably just preloading it, making it less or more difficult for the valve to open. couldn't hurt to play around with it a little bit and see if it makes any difference.

 

Yes, if you loosen it, the compressor surge should stop. The reason it is doing that is because it is too tight and the BOV isn't opening at lower psi.

 

So is there a possibility that it could be a vacuum leak in which case the BOV isn't getting enough pull to open? Because I never messed with it and it used to be working just fine...

Shouldn't I just loosen the spring all the way if it's that beneficial or is there some reason that it needs to be a little stiff?

 

You should be able to tell if you have a vacuum leak, if the car isn't boosting as it was before. You might be able to hear a sound as well, but if you aren't losing boost, you don't have a serious leak.

I'm not quite sure but if you loosen the spring all the way I think the BOV will release pressurized air prematurely. You have to have it on the right setting.

randy

 

fluttering at low boost is normal. probably no boost leak. just your adjustment screw is too loose. like mentioned, the screw is to increase the spring rate so it opens at higher boost. when the bolt is too tight, you'll get more turbo surge than the BOV opening during mid-low boost. It may take some trial and error to play around w/ the screw until your desired rate.

 

I should probably clear that up...

It doesn't flutter when building low boost, only when I build low boost and then get off the gas. Basically when it's supposed to open and blow off it does but flutters while doing so. I don't understand how the spring could be too loose right now when I haven't messed with it since I got the car and it used to work fine. Thats why I think it might be a vacuum leak... What is the best way to check for a vacuum leak in the BOV vacuum line?

 

i had a problem similar to this, the way my BOV was mounted on the greddy elbow w/ flange it the screw actually hit my strut tower bent the adjuster, and did the same thing yours is doing, make sure your BOV isnt too close to the tower.

 

Silly question, but is your car an Auto or Manual?

When my car was AT, my Greddy BOV, it would make that fluttering sound in low boost (like 4-5 psi). In full boost, it didnt make that sound. I've tried adjusting the screw on the top of the BOV, but it kept fluttering on low boost. I believe its because the AT is always on boost, it will always flutter a bit on lower boost...so I just didn't worry about it. After I did the MT swap, the BOV doesn't make that flutter sound on low boost or high and its the same adjust setting on the BOV.

As everyone suggested, try adjusting the screw on the top, but I think if it's an AT, it will flutter on low boost regardless...so adjust so it doen't make the flutter sound on high boost .

 

You said there was a possibility someone could have messed with it at a show, at least that's why I had brought up the adjustment possibly being off.

To test for a vacuum leak get some starting fluid and while your car is idling spray it around the areas you think may have a leak. If the idle drops that means some of the starting fluid was sucked in the leak. At least at that point you KNOW there is a leak and have a general idea where it is to start looking for it.

If you loosen the spring to much you run the risk of pushing the BOV open while on boost and effectively creating a boost leak. At least that's the way I always understood it .

Good luck, report back with more info when you've got it!

 

Ok slight issue... I went to see if the screw needed to be loosened and to my dismay, it's already as loose as possible. So I went for a short drive to see if it was still doing it and when I built 7psi of boost the bov sounded like it normally does with a nice "whoosh" but as the "whoosh" was ending it started fluttering again and I came to the conclusion that it really was compressor surge. So I took a look around and found out that there appears to be a hole in the back of the BOV... Does any one know if this hole is supposed to be plugged with something?

 

Well Rotary Performance opened today and I went over to ask about my issue and I brought the BOV with me. Within 10 seconds of looking at it Chris came to the conclusion that the diaphragm of all things is torn.

Just for everyones reference apparently if you blow or suck on the nipple for the BOV's vacuum line and air can freely move in and out of the BOV, then your diaphragm is the issue. On the other hand a diaphragm failing is not by any means a common occurrence.

It's an $80 part which kinda pisses me off but ehh, what can you do about it?

 

If you want to upgrade, Synapse Engineering's Synchonic BOV is diaphramless.

 

I like Tial BOV's, are Tials diaphragm-less?

 

Did u find out about the hole in the back of the BOV?
mine is like that aswell and has been since new, always kinda wondered about it

 

No tial uses diaphrams, but I think they have proven their quality over the years so it's kind of irrelevent unless you are obsessed with using a diaphramless BOV.

That hole could be some sort of recirc option? is it threaded? if it is for recirculating back into the intake You would put some sort of fitting on it and then run a vacuum line to the intake pipe between the turbo's and filter.

 

The diaphragm in my Greddy Type-S failed back in my old FC and caused the same symptoms you're describing.

 

the Greddy type-R is a heavy duty race BOV.

it has a really stiff spring to prevent it from opening on low boost levels.

what you hear is compressor surge.

low boost levels won't hurt your turbo too badly. since the BOV isn't opening to keep your boost level between shifts you don't have to build boost from zero psi everytime. instead you start at 7psi.

its a good thing as far as performance goes.

 

Ok, the hole in the back of the BOV is threaded and is used for certain cars that require both a push and pull effect on the diaphragm. You know how the vacuum line pulls on the top of the diaphragm to open it? Well, the other hole is positioned below the diaphragm and certain cars use what I would call a "boost line" that helps move the diaphragm by pushing up as the vacuum pulls up. Get it? On our cars this hole needs to be left open so that when the vacuum pulls the diaphragm up, the air that is displaced below the diaphragm can be replaced with atmospheric air and when it closes the air can come back out.

What I said earlier about blowing or sucking on the vacuum nipple refers to whether air moves in and out of this hole. I don't think any human has the ability to suck hard enough to open the BOV in the first place so if you try and you're actually able to inhale air, then that means that the air you are inhaling is coming in to the BOV through that open hole and passing through the broken diaphragm (which it shouldn't do). Same goes for blowing into it. I blew into mine and I could also hear the air rushing through.

 

I'm not saying you're wrong but I was always told that the BOV should always open when you're off throttle because compressor surge of any amount slows down the rotation of the turbo wheel. If you open the BOV and let the air freely escape then you're turbo wheel doesn't slow down and as soon as you get back on the throttle the BOV closes and the turbo is already spinning at a really fast speed in order to quickly re-pressurize the system. Compressor surge is supposed to always reduce threshold boost response...

 

the springs are to keep it from opening under vacuum...holy crap guys