BOV Flutter
#24
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. :-)
#27
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.
#29
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)
#30
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.
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.
#34
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.
#36
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.
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.
#37
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
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
#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.
#39
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)
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)
#40
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?