Fluttering sound from BOV - Subaru Impreza GC8 & RS Forum & Community: RS25.com

ACraPPyRS · 11-05-2006, 08:56 PM

Since I turbo'd my car when my BOV vents it makes a weird "fluttering sound". I thought the problem was the cheap BOV I had, so I bought a $250 Tial BOV and it is making the exact same sound as the $20 BOV from ebay. Has anyone experienced this before. I'm currently running a gt25r (AVO kit) with a FMIC, and it should be boosting at about 4 psi (I think that's what it comes set at from Rallitek). Is that the sound it makes under such low PSI or is there a problem here. PLease help

KAX · 11-05-2006, 10:28 PM

probably the low psi. its either the air squeaking out of the BOv or its the turbo surging because the psi isnt enough to open the BOV. ask Rallitek what they think about it if its their turbo kit.

**TipStylez** · 11-05-2006, 10:48 PM

Dose it sound like a bird is flapping its wings when you get off the gas?

If so..sounds like like a surge.

Xanaduce · 11-06-2006, 06:47 AM

I had a leak in my last car, it sounded like amonsorous laugh. My suggestion, make a cap to go over your turbo inlet, and put an air fitting like on a car tire, to go in it. Tighten it with a clamp, and get an air compressor, set a valve to your max psi on the air compressor, (as a boost controller will leak any excess,) and pump your piping up. usually works great with 2 people, as one can watch to boost gauge so you dont' over do it with the compressed air. The you listen for leaks, and seal/replace gaskets fittings appropriately. If that doesn't do it, and you have an adjustable BOV, change the settings, A loose spring could cause it to flutter, however be careful to not to overtighten it, overtightening a BOV's Adjustment can cause surge as well.

ACraPPyRS · 11-06-2006, 09:04 AM

Quote:

Originally Posted by TipStylez

Dose it sound like a bird is flapping its wings when you get off the gas?

If so..sounds like like a surge.

Yes, it does sound kind of like the flapping of a birds wings. What would cause compressor surge?

KAX · 11-06-2006, 09:54 AM

compressor surge is when the air from your intercooler is getting pushed back into the turbo, because the BOV or BPV is not opening and theres no where else for it to go except back into the turbo.

you probably need to get a softer spring for the BOV or something like that. But like I said, if its Ralliteks turbo, they should be able to help you out the most, because i dont know the specs on it.

ACraPPyRS · 11-06-2006, 08:04 PM

So with compressor surge it's just the BOV not opening and the excess air returning to the turbo? But that can't be my problem because the BOV is venting..I can fell air come out of it when my friend revvs it. It just makes a reallly weird noise. Maybe low PSI BOVS sound like that? I could really use some input from someone with an rs-t with a similar setup to mine.

**TipStylez** · 11-06-2006, 08:39 PM

Is your BOV adjustable?

Compressor surge is bad for your turbo and a BOV will just make you lose hp when your only pushing 4psi.

FuJi K · 11-06-2006, 08:44 PM

I DO notice that the BOV flutters at lower psi. At higher boost it doesn't flutter. This is with a Greddy Type S BOV on a EJ20G swapped L. The TurboXS on it now does flutter a little too at lower psi, but not as much as the Greddy one.

I've heard the BOV flutter too with cars revving in neutral where there's less load on the engine, thus less boost. BUT when they're in gear and there's more load and more boost, it is a pshhHHHH or whistle like the HKS..

Aphex28 · 11-06-2006, 08:49 PM

It sounds like you're describing surge. Here's some vids of my kit, the first video is of surge, you can hear it after i rev... a fluttering noise...

Second video is how it should sound. thats a Turbo XS type H bov.
it's of me going partly through 1st and then all of second. then some 3rd and 4th. hehehe 2nd passes so fast.
It's just a TD04, stock engine with HKS dumped External Wastegate and Emanage. 6psi

If yours sounds like the first video then it sounds like your bov isn't getting vaccum which it should get at the nipple on the top of the bov.
Try rerouting a new line from a different source into the bov and see how that works.

Also try using the same line your boost gauge is hooked up into, ie one of the 2 lines on the passenger rear side of the intake manifold, the bottom one i believe. If that doesnt work, try oiling your bov or using washers/cutting the spring

11-05-2006, 08:56 PM	#1 (permalink)
ACraPPyRS 2.2L Turbo Car: 2005 RSTi Fav Mod: EJ257 :) My: Subaru Parts Join Date: Jul 2006 Location: Bronx,NY/Bloomington, IN Trader Rating: (4) Posts: 2,154	Fluttering sound from BOV Since I turbo'd my car when my BOV vents it makes a weird "fluttering sound". I thought the problem was the cheap BOV I had, so I bought a $250 Tial BOV and it is making the exact same sound as the $20 BOV from ebay. Has anyone experienced this before. I'm currently running a gt25r (AVO kit) with a FMIC, and it should be boosting at about 4 psi (I think that's what it comes set at from Rallitek). Is that the sound it makes under such low PSI or is there a problem here. PLease help __________________ Phi Kappa Sigma!

11-05-2006, 10:48 PM	#3 (permalink)
TipStylez XCELMotorsports! Car: Everything nice Fav Mod: Suspenson My: Subaru Parts Join Date: Jul 2005 Location: Seattle Trader Rating: (0) Posts: 1,035	Dose it sound like a bird is flapping its wings when you get off the gas? If so..sounds like like a surge. __________________ XCELMotorsports.com

11-06-2006, 06:47 AM	#4 (permalink)
Xanaduce 2.5L Car: 2005 Saab 92x Linear My: Subaru Parts Join Date: Jun 2005 Trader Rating: (2) Posts: 257	I had a leak in my last car, it sounded like amonsorous laugh. My suggestion, make a cap to go over your turbo inlet, and put an air fitting like on a car tire, to go in it. Tighten it with a clamp, and get an air compressor, set a valve to your max psi on the air compressor, (as a boost controller will leak any excess,) and pump your piping up. usually works great with 2 people, as one can watch to boost gauge so you dont' over do it with the compressed air. The you listen for leaks, and seal/replace gaskets fittings appropriately. If that doesn't do it, and you have an adjustable BOV, change the settings, A loose spring could cause it to flutter, however be careful to not to overtighten it, overtightening a BOV's Adjustment can cause surge as well. __________________ "Average citizens are over medicated, over caffeinated and over stressed." courtesy of Svek.

11-06-2006, 08:04 PM	#7 (permalink)
ACraPPyRS 2.2L Turbo Car: 2005 RSTi Fav Mod: EJ257 :) My: Subaru Parts Join Date: Jul 2006 Location: Bronx,NY/Bloomington, IN Trader Rating: (4) Posts: 2,154	So with compressor surge it's just the BOV not opening and the excess air returning to the turbo? But that can't be my problem because the BOV is venting..I can fell air come out of it when my friend revvs it. It just makes a reallly weird noise. Maybe low PSI BOVS sound like that? I could really use some input from someone with an rs-t with a similar setup to mine. __________________ Phi Kappa Sigma!

11-06-2006, 08:39 PM	#8 (permalink)
TipStylez XCELMotorsports! Car: Everything nice Fav Mod: Suspenson My: Subaru Parts Join Date: Jul 2005 Location: Seattle Trader Rating: (0) Posts: 1,035	Is your BOV adjustable? Compressor surge is bad for your turbo and a BOV will just make you lose hp when your only pushing 4psi. __________________ XCELMotorsports.com

11-05-2006, 10:28 PM	#2 (permalink)
KAX 2.7L Car: 2000 BRP Subaru Impreza 2.5RS Fav Mod: 2002 WRX Swap My: Subaru Parts Join Date: Oct 2006 Location: Orlando, FL Trader Rating: (6) Posts: 486	probably the low psi. its either the air squeaking out of the BOv or its the turbo surging because the psi isnt enough to open the BOV. ask Rallitek what they think about it if its their turbo kit.

11-06-2006, 09:54 AM	#6 (permalink)
KAX 2.7L Car: 2000 BRP Subaru Impreza 2.5RS Fav Mod: 2002 WRX Swap My: Subaru Parts Join Date: Oct 2006 Location: Orlando, FL Trader Rating: (6) Posts: 486	compressor surge is when the air from your intercooler is getting pushed back into the turbo, because the BOV or BPV is not opening and theres no where else for it to go except back into the turbo. you probably need to get a softer spring for the BOV or something like that. But like I said, if its Ralliteks turbo, they should be able to help you out the most, because i dont know the specs on it.

11-06-2006, 08:44 PM	#9 (permalink)
FuJi K 2.5L RS-T Car: MY99 GF4 EJ225 EVO3-16G My: Subaru Parts My: Subaru Blog Join Date: Dec 2001 Location: St. Paul MN United States of America Trader Rating: (2) Posts: 4,246	I DO notice that the BOV flutters at lower psi. At higher boost it doesn't flutter. This is with a Greddy Type S BOV on a EJ20G swapped L. The TurboXS on it now does flutter a little too at lower psi, but not as much as the Greddy one. I've heard the BOV flutter too with cars revving in neutral where there's less load on the engine, thus less boost. BUT when they're in gear and there's more load and more boost, it is a pshhHHHH or whistle like the HKS.. __________________ It's about the Top End!!!

11-06-2006, 08:49 PM	#10 (permalink)
Aphex28 2.2L Turbo Car: 00 STM jdm swapoos Fav Mod: bewbz My: Subaru Parts Join Date: Jun 2004 Location: Pepperell, MA Trader Rating: (30) Posts: 3,764	It sounds like you're describing surge. Here's some vids of my kit, the first video is of surge, you can hear it after i rev... a fluttering noise... Second video is how it should sound. thats a Turbo XS type H bov. it's of me going partly through 1st and then all of second. then some 3rd and 4th. hehehe 2nd passes so fast. It's just a TD04, stock engine with HKS dumped External Wastegate and Emanage. 6psi If yours sounds like the first video then it sounds like your bov isn't getting vaccum which it should get at the nipple on the top of the bov. Try rerouting a new line from a different source into the bov and see how that works. Also try using the same line your boost gauge is hooked up into, ie one of the 2 lines on the passenger rear side of the intake manifold, the bottom one i believe. If that doesnt work, try oiling your bov or using washers/cutting the spring Last edited by Aphex28; 11-06-2006 at 08:51 PM..

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