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Old 05-30-2008, 12:29 PM   #21
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When you guys are describing flutter are you talking about compressor surge (gobble gobble)?

I think it's time for a sounds clip.
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Old 05-30-2008, 12:53 PM   #22
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just buy a real bov ,,

both me a friend had flutter, and we both switched to real bov's

i got the turbo smart series 2, and he got that stupid hks one

but they work great. i vta with a afm still in place with no stalling issues, no hiccups, and no flutter or surge
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Old 05-30-2008, 01:50 PM   #23
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Originally Posted by jayc72 View Post
When you guys are describing flutter are you talking about compressor surge (gobble gobble)?

I think it's time for a sounds clip.
I'm 99% sure they are talking about flutter.. aka.. blow off.. then flutter as the valve attempts to close. Pretty common on the XS
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Old 05-30-2008, 01:55 PM   #24
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Quote:
Originally Posted by jayc72 View Post
When you guys are describing flutter are you talking about compressor surge (gobble gobble)?

I think it's time for a sounds clip.
+1. I'm still not sure what they are talking about, though I think it's it.


Also, in the 80's, 90's, I had lots of friends with no BOV at all, tons of surge (gobble) on every shift, and there was no broken turbos that I saw.

If it's at idle, here's what you do to fix it: Turn up your stereo. Seriously, it's not like you're slamming a high speed turbo to a sudden stop.

If it's happening as you flick-shift from 3rd to fourth at 18 psi and full revs, then you should do something about it.

And if it's open at idle, see if air is coming out. Otherwise, it's sucking in. And your blinging K&N "filtercharger" is doing nothing while you suck in road debris through your BOV. :-)
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Old 05-30-2008, 01:57 PM   #25
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Originally Posted by Newbsauce View Post
flutter.. aka.. blow off.. then flutter
flutter and blow off are different things.

Let's try "Surge" (i.e. the gobble gobble sound of the turbo stalling, dumping pressure OUT the air filter) and "vent" where air comes *out* of the port in the side of the blow off valve.
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Old 05-30-2008, 02:05 PM   #26
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And this is why I want a sound clip
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Old 05-30-2008, 02:14 PM   #27
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flutter and blow off are different things.

Let's try "Surge" (i.e. the gobble gobble sound of the turbo stalling, dumping pressure OUT the air filter) and "vent" where air comes *out* of the port in the side of the blow off valve.
I know exactly what surge is..and I was defining the sound in sequence. The flutter generally occurs after the initial "vent out of the port of the side of the blow off valve". I would strongly disagree with surge if the damn thing is leaking at idle.

I was looking for a sound to demonstrate, but i found this and though I would show. Before Abe jumps on my case as me calling this flutter.. I'm not... Here the fluttering is occurring before the actual purge. Plus the term they use is just funny.
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Old 05-30-2008, 02:49 PM   #28
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Originally Posted by Newbsauce View Post
I'm 99% sure they are talking about flutter.. aka.. blow off.. then flutter as the valve attempts to close. Pretty common on the XS
I have the TurboXS and it doesnt flutter the way you describe, it surges for half a second at low rpm but thats it.
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Old 05-30-2008, 03:04 PM   #29
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Originally Posted by Newbsauce View Post
I was looking for a sound to demonstrate, but i found this and though I would show. Before Abe jumps on my case as me calling this flutter.. I'm not... Here the fluttering is occurring before the actual purge. Plus the term they use is just funny.
Awesome, not only is that a good find, it also warms my heart to see a WRX all dolled up, pulling boost then failing to gain on a raised SUV. :-P

I imagine that place has some tips on curing the problem. Perhaps moving it closer to the throttle body helps. As I said, a quick lift always helps me. Bigger line to the BOV might be good, but yeah, some BOV's are just crap, too.

(Not trying to get on anyone's case, somehow I read that earlier statement to mean those were the same thing)
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Old 05-30-2008, 03:42 PM   #30
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Mines is the BOV flutter, it sounds exactly like how the wrx bov does but without the dump at the end, well most of the time. Well, the flutter on mines is a lot faster and lasts for about 2 seconds. I'm sure because of the flutter there are pressure waves still going to the compressor trying to stall it, but not as bad.

I'm gonna try that ebay Type S as a lot of my friends have had success with these. If that doesn't work, all i'm out is only $36 so no big deal. I can prolly just sell this one and get either the real thing or some other BOV that fits.

Oh, and I know how real bad compressor surge sounds like. My friends ghetto turbocharged 240 has no BOV and he likes to boost it to 15psi. That thing sounds like you're trying to kill a turkey, I crack up all the time I hear it. He thinks its cool so just keeps it that way.
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Old 05-30-2008, 04:01 PM   #31
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Yeah - I wonder if the vacuum signal is getting to your BOV? It's supposed to actively open when manifold vacuum pulls on it.
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Old 05-30-2008, 04:04 PM   #32
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In my mind to get rid of the flutter, a softer spring should be employed? I get this flutter at low RPM occasionally.
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Old 05-30-2008, 04:05 PM   #33
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Yeah - I wonder if the vacuum signal is getting to your BOV? It's supposed to actively open when manifold vacuum pulls on it.
If that were the case he'd get gobble gobble.
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Old 05-30-2008, 04:11 PM   #34
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At first, I had no washers in my BOV. When I put washers in, it wouldn't even open at all until I hit like 7-8 psi. Once I cut the spring it started to open at around 4 psi. Then I cut the spring again and started to open at around 2 psi, but started to leak at idle. It was sucking in air. So in order to fix that I put in 2 washers. Now it blows off better and doesn't leak at idle, although the flutter is still present. Its more so during high boost runs of 8+ psi. I also noticed that when I lift off quick it does the flutter more so than when I lift off slow. If I lift off slow then it does a nice but soft dump with no flutter.
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Old 05-30-2008, 04:16 PM   #35
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I wanted to try that at first, but didn't know where about to get a softer spring. I wouldn't mind trying a softer spring. I guess I should try looking for one. Anyone got any suggestions?
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Old 05-30-2008, 04:40 PM   #36
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Originally Posted by supersuk View Post
At first, I had no washers in my BOV. When I put washers in, it wouldn't even open at all until I hit like 7-8 psi. Once I cut the spring it started to open at around 4 psi. Then I cut the spring again and started to open at around 2 psi, but started to leak at idle. It was sucking in air. So in order to fix that I put in 2 washers. Now it blows off better and doesn't leak at idle, although the flutter is still present. Its more so during high boost runs of 8+ psi. I also noticed that when I lift off quick it does the flutter more so than when I lift off slow. If I lift off slow then it does a nice but soft dump with no flutter.
Something is weird there... Lifting fast just means you actually have more air that NEEDS blowing off, and I think that's exposing your problem. My guess is either the hole is too small (but unlikely, since there's no much air at idle).

Having the spring not even touching, which sounds like what you're doing, will help it open easier, but open less under real pressure. This probably hurts the function of the BOV when it actually matters, but not so much in traffic.

That's the distinction I think. While lots of very hard surge is bad for the turbo, the truth is, a little bit won't hurt it. The real purpose of a BOV is to keep you from having to spool up the turbo again after a shift. It's not for longevity, though it helps there, it's a performance mod.

My buddie's dodge I was talking about, he had to respool after every shift. That meant a second or more of off-boost after every shift, slowing things down alot. After a hard shift in my miata, I'm at full boost in a fraction of a second. MUCH BETTER, and all thanks to the BOV.

For that, you want it to open far, and wide, but not to open too early (idle, etc). So a weak spring with some preload, even if it makes it surge in stop and go, is probably the way to go, if you have to pick.
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Old 05-30-2008, 04:54 PM   #37
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The spring in my bov is about twice as long as the bov itself even after I cut coils off. The washers in the bov help to effectively increase amount of vaccum needed to open it during idle.

Think of the turbo XS BOV as a cylinder with a piston in the middle. One side is hooked up to the intercooler pipes while the other side hooked up to the intake manifold with a spring on that side. When the engine revs up and builds boost and you let off the throttle, the pressure differential between either side of the throttle plate should be what opens the BOV. The vacuum from the intake manifold pulls the piston while the boost pressure inside the intercooler pipes push the piston open. While under boost, the pressure from the intake manifold and the spring push on the piston while the pressure from the intercooler pipes also push on the piston. I think that the reason the BOV flutters is because the spring in the BOV is not matched to your system. Its like a shock that doesn't damp enough and has to much rebound.

The only way I think to make this thing work better would prolly be a softer spring or maybe a shorter spring with the same spring rate. Instead of wanting to trial and error, i opted the easy way out and just bought a new one. Ha Ha
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Old 05-30-2008, 05:21 PM   #38
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You're fucked. Flutter is a part of life with most BOVs. Just WOT all the time and get nice poowshes and be happier or like the purr like a kitty noise your badass turbo miata makes. Chicks will like your car even more. The end. The video had a synapse BOV. It was an add for their BOV. It's sphecial.
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Old 05-30-2008, 07:20 PM   #39
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My car doesn't surge, almost never. It's the 'old style' FM BOV.

BTW, if you've got hardly any spring in there, what happens when you do this:

Light boost, or easing off the throttle. Pressure in the manifold, say, 4 psi. In the IC piping, 14 psi, across the throttle plates there's a drop of 10 psi. Your BOV will open.

Now your turbo is pissing air out of the lines. Doesn't that tick you off? (Ok, I don't think it really matters)
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Old 05-30-2008, 07:58 PM   #40
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If you can make that condition happen, which is highly unlikely. At light throttle, your car will not make that much boost anyways unless you have a tiny little turbo. I don't think you can have that kind of pressure differential on either side of the throttle body unless you make the throttle body pretty small and it just opens up into a huge manifold (like enormous!!). Only vacuum and boost. It also won't matter if you're easing off the throttle. Am I making any sense?
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