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Old 05-28-2008, 03:22 PM   #1
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Default BOV Flutter

I got a question, what causes BOV flutter between two different turbos. I used to have a Mitsubishi T25 turbo setup with a Turbo XS BOV. This setup didn't flutter at all. When I changed to a T3 setup, my BOV flutters like a ****. Even though I try to install it with a lighter spring it still flutters. What causes this?
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Old 05-28-2008, 04:00 PM   #2
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less boost to help the diaphragm or piston at a given rpm maybe?
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Old 05-28-2008, 04:03 PM   #3
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I think he means flutter at idle.
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Old 05-28-2008, 04:25 PM   #4
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I think he means flutter on lift, or the BOV is lagging to open.
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Old 05-28-2008, 04:26 PM   #5
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No flutter at idle. With my current T3 it flutters everytime when I shift. When I had my old mitsu T25, it would never flutter.

I'm assuming that since the T3 is like 30 million times larger than the T25, it spools a lot less at lower rpms causing the flutter (less boost at a given lower rpm). The BOV's lightest setting might still be to heavy during light boost. Therefore, the only way that I might fix this is to find a lighter spring, but might cause other problems such as leaking during idle. Please correct me if I'm wrong.
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Old 05-28-2008, 04:31 PM   #6
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yes, and I have the same problem with my TurboXS. Flutters at low boost/low rpm doesnt at higher rpm.

Its all about how fast vacuum builds to pull the valve open.
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Old 05-28-2008, 04:40 PM   #7
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I already cut off 3 coils and it did help a little, doesn't flutter as much. Frackin BOV, I'm gonna try cut the spring more to make it smaller. See if that helps.
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Old 05-29-2008, 09:50 AM   #8
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Ok, cut off as much coils that I could from the spring before it started to leak at idle. Installed some washers to prevent it from leaking at idle. BOV now doesn't flutter on low boost. Only on high boost does it flutter. Makes me think the BOV that I have is undersized for my application. Damn sucks.
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Old 05-29-2008, 12:39 PM   #9
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Only 1 way to solve this flutter..... turn up the boost and hit full boost all the time
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Old 05-29-2008, 04:47 PM   #10
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Ha ha, I don't really feel like damaging my turbo since the BOV flutters on high boost. I noticed that with the T3 turbo set up the BOV isn't as loud as the T25. I really like it quiet like this. I may change my BOV to something different such as the knockoff greddy's since people here are running it without the flutter.
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Old 05-29-2008, 06:08 PM   #11
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How much does yours flutter?

Is it like a long lasting flutter or is it like a second of flutter and then it releases normally?

have you tried dismantling ur valve and just making sure it isnt binding?
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Old 05-29-2008, 06:14 PM   #12
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Bailey twin piston dump valves are designed to stop flutter at tick over I think.
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Old 05-29-2008, 06:40 PM   #13
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On high boost, the BOV flutters for a good 2 seconds then I don't hear anything after that (like BOV valve is closed, but I know its not). Noticed that sometimes on low boost it flutters for about a second then opens regular. I've taken the BOV apart many times, oiled it and made sure there was no binding. It operates smooth. I just purchased one of those Greddy knockoffs on ebay and see if that relieves the problem. Seems like the BOV ports are a lot larger on the Greddy than the turbo xs, plus, it was only $35 with everything I need to install it. Can't beat that!!
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Old 05-29-2008, 07:31 PM   #14
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Quote:
Originally Posted by supersuk View Post
Ok, cut off as much coils that I could from the spring before it started to leak at idle. Installed some washers to prevent it from leaking at idle. BOV now doesn't flutter on low boost. Only on high boost does it flutter. Makes me think the BOV that I have is undersized for my application. Damn sucks.
By 'flutter' you mean air coming back out of the turbo? i.e. turkey-sound from the turbo when you close the throttle? If it's going for seconds, then it's not just the momentum of the turbo.

I've noticed on my FM BOV that it gets dirty, cleaning it helps.

BTW, cutting a spring *raises* it's spring rate. If you're shortening it, that's a winning battle, but cutting it and adding washers makes it stiffer.

Sometimes I worry about mine opening under boost though. :-) I've got it pretty light and I really have few issues with it - if I want it to blow off I lift quick, and if I don't I lift slow.
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Old 05-29-2008, 10:01 PM   #15
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Quote:
Originally Posted by supersuk View Post
On high boost, the BOV flutters for a good 2 seconds then I don't hear anything after that (like BOV valve is closed, but I know its not). Noticed that sometimes on low boost it flutters for about a second then opens regular. I've taken the BOV apart many times, oiled it and made sure there was no binding. It operates smooth. I just purchased one of those Greddy knockoffs on ebay and see if that relieves the problem. Seems like the BOV ports are a lot larger on the Greddy than the turbo xs, plus, it was only $35 with everything I need to install it. Can't beat that!!
How are you going to install it in place of urs?

LInk me to the auction, I may want to get one as well.
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Old 05-29-2008, 11:03 PM   #16
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AbeFM:

Correct, cutting the spring does make it stiffer but in my case for some reason it works better. Maybe because its stiffer, it resists the surging better? If the spring is softer, it could possibly intensify the surge acting like a rubberband? Although a softer spring would probably open easier under vaccum from the manifold behind the throttle body and boost pressure inside the intercooler piping. It does open ever so slightly at idle, but it makes a whole lot less turkey gobble (flutter) and can hear a soft wooshing noise now. Still sucks though cause the flutter is still there. I want to get rid of it completely. It may sound pretty cool, but in the end I know it is detrimental to my turbo.

Well, this BOV is brand new and isn't dirty at all. Maybe I just have to somehow break it in and wear the spring down allowing it to sag.



Sam:

this is the one I am going to purchase:

http://cgi.ebay.com/ebaymotors/Turbo...spagenameZWDVW

This one is a cast one:

http://cgi.ebay.com/ebaymotors/Bov-B...spagenameZWDVW

Noticed that there are a couple different types of type S BOV's some are cast with CNC'd parts, others are completely CNC'd. I opted to purchase the completely CNC'd. You can also find them with mild steel bungs, SS bungs, or just full pipes with the bung welded on. Right now I have the Turbo XS weld on bung welded to the intercooler pipe. The Ebay Type S weld on bung appears to be a little larger than the turbo xs one so I'll just cut it out and weld the new one on. Simple. Hope this **** works.

Last edited by supersuk; 05-29-2008 at 11:13 PM.
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Old 05-30-2008, 01:04 AM   #17
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I see the second one has a weld on bung like the turbo xs, but I Just dont see how the greddy bov is supposed to mate to it if it uses its own proprietary flange.

I was thinking of getting another valve but without having to remove my welded in bung, just throw a coupler on it with some tbolt clamps.
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Old 05-30-2008, 03:54 AM   #18
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I was looking for a BOV with the largest opening possible. The Greddy Type S looks big enough at about 34mm.
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Old 05-30-2008, 10:02 AM   #19
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Quote:
Originally Posted by supersuk View Post
AbeFM:

Sam:

this is the one I am going to purchase:

http://cgi.ebay.com/ebaymotors/Turbo...spagenameZWDVW

This one is a cast one:

http://cgi.ebay.com/ebaymotors/Bov-B...spagenameZWDVW
1> The TurboXS RFL is notorious for flutter, because it does not have the attached vacuum line that the S does to pull it shut. Its a hell of a BOV for sound, but for functionality, use something with that vacuum port like the S has.

2> I have experience with both the ebay S and the real S BOVs. I did not run the ebay S long enough to really test whether or not it was the cause of my vacuum issues, but I can say that I am far more impressed with the real S BOV as far as vacuum and sound.
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Old 05-30-2008, 10:57 AM   #20
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hey supersuk, heres a question for you.

How many shims are you using in your TurboXS? I went from four to two, and its cracked 1mm at idle. Flutters for half a second in low rpms.

Either way, let me know how that knockoff works for you. If it works well then I will pick one up also.
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