BOV Flutter
 

Since I put a Forge BOV on my Evo I've been having this problem. The BOV flutters under any sort of PARTIAL throttle. The worst is on the freeway. If I give the car partial throttle to accellerate through traffic a bit, and the car builds a small amount of boost (1-5psi or so), the car bucks back and forth, building boost and blowing it off/bypassing air continuously.

The other thing that happens is under partial throttle, higher boost, higher rpms (4500+). The BOV seems to flutter. No bucking, just fluttering.

The worst is when both of these are combined (little of each case above going on).

I also have a hallman MBC hooked up. Both the MBC and Forge are fed manifold pressure, but from seperate feed lines.

Anyone have any advice? Here's some cell-phone vids of these conditions:

http://www.scheides.com/misc/MOV00012.3gp
http://www.scheides.com/misc/MOV00016.3gp

Re: BOV Flutter
 

Is it a recirc style?

Re: BOV Flutter
 

How do I view these bad boys? Not familiar with the Forge BOV but for the flutter issue, isn't there a way to adjust the hardness/softness?

Re: BOV Flutter
 

Yes, sorry it's recirculating bypass valve/BOV as seen in this pic (my car):

http://www.scheides.com/albums/evo8/DSC00607.sized.jpg

You should be able to view those vids in quicktime.

Re: BOV Flutter
 

I have a Forge and haven't had any similar issues, but def. check what colored spring you should be running for the amount of boost you are running.
(They change hardness of BOV)

Re: BOV Flutter
 

Perhaps the vacuum line is hooked up to the wrong port on the TB or manifold? the only other thing is the spring strength, if you need a temporary fix, take the sping out and stretch it out so it's longer. or toss some washers in there like a TurboXS.

Re: BOV Flutter
 

Yea sounds like a defective spring.

Re: BOV Flutter
 

I dont know what the inside to this BOV looks like but I read that for the Greddy BOV there are 2 springs and on EVOs you are sapose to remove one of them to not have this happen. Im gonna try and look for where I read that.

Heres the website...
http://www.evomoto.com/tech_info.php?tPath=1&tech_id=7

Re: BOV Flutter
 

Looking at the pic it looks like you have a T fitting off the BOV line. Did you change that or is it still like that. If its still like that try giving it its own source.

Re: BOV Flutter
 

My EVO does/did the same thing with the same BOV.

Re: BOV Flutter
 

How does it run with the bov disconnected and line pluged?

Has it been doing this from day one?

Re: BOV Flutter
 

In the pic I'm running a t-fitting. I'm currently running seperate runs from the intake manifold to the MBC and BOV. I've swapped springs and added washers/spacers (just like I said above) to no avail.

This has been happening since I installed the forge unit.

Re: BOV Flutter
 

If this happens to both you and Nash it must be a common problem. What do the guys on the EVO board(s) say?

Re: BOV Flutter
 

Some people seem to have similar issues, but no one seems to have it as bad as I have...I'm going to do some boost leak tests (again) and possibly swap on the stock BOV this weekend just to see what will happen.

Re: BOV Flutter
 

How about a different brand of BOV? If people have problems with them, why do people continue to use them?

Does the stock BOV leak like a 2G?

Re: BOV Flutter
 

I've heard nothing of this sillyness when I bought my forge. Nash says his car did it, but I can't imagine it is as bad as my car is. When driving at the limit, having partial throttle control is absolutly necessary, and it just isn't there on my car. The car falls on its face and I feel like I'm gonna die if I push the limit too much.

The stock BOV doesn't leak as bad as a 2G, but it is cheapo plastic, so I imagine it won't hold up to much abuse.

Re: BOV Flutter
 

The IX's have a different BOV and so far people think it's better. Just another option to consider.

Re: BOV Flutter
 

Well, after swapping in every possible spring/shim combo, several boost leak tests, and a bunch of just driving, I gave up. I swapped in the stock DV/BOV and the fluttering is gone.

WTF should I do now? The stock DV is not going to hold up to what I have in store for it. New Forge? Go for something else? I'd go straight to a Tial, but I am still running the stock MAF. :P

Re: BOV Flutter
 

Hks

Re: BOV Flutter
 

I'm gonna try getting a bung welded onto my LICP and see if that helps. I'm thinking the MBC and BOV seeing the same boost pressure (i.e. manifold pressure, after the TB) is causing some sort of weird loop: the BOV opening, dropping pressure in the system and making the MBC ball/spring close thus shutting the wastegate, which instantly causes boost to rise again. As this happens, the pressure in the IC piping is slightly higher than in the manifold, causing the BOV to open, dropping pressure in the IC piping and ......ah fuck it I'm gonna go buy a FORD :(