bov sounds

[Guest]

got my new bov to replcae the fatory one on the primary before i put the engine back in. What will it be sounding like with a piston bov on the secondary and a sequential on the primary??

[Leese]

In answer to your question - Sorry dude I'm not sure...

I have an HKS SSQV BOV on my twin turbo Legacy, am I supposed to have one for each turbo? (As there's only one BOV under the bonnet...) Sorry for the dumb question - I'm new to the whole twin turbo thing...

[Pappu1]

older pre 99/98 i think TT had 2 blow off - secondary and primary - always replace the secondary to atm if want to

on the newer tt they had only 1 blow off so you can change that - either piston or ssq dont matter - ur preference really

[G-unit]

dont touch the secondary 1, u only need 1 which goes on the passanger side of car, had a ssqv on my TT sounds like all ssqv on most cars

[Joker]

yup only one BOV on passenger side - I have seen writings from ReubenH that the drivers side BOV has more to do with the Turbo swap-over systen, ie DONT TOUCH IT

[Guest]

the one on the drivers side, when the butterfly in the intercooler pipe is closed it think this blowoffvalve prevents excese presure build up, maby from the turbo still spooling when its exhaust gas is shut off to it? to prevent damage to the turbo i guess?

just from looking the diagrams i got, its more than likely im wrong hahaha

but, i whould leave it alone.

-smurff

[Guest]

sweet as dudes i'll see how she sounds and if its crap i'll let you know more hopefully this thursday when all the heads and stuff are ready to go back on

[ReubenH]

Do not touch the second BOV down by the secondary turbo. There was a thread about this a few weeks ago:

http://www.clubsub.org.nz/forum/index.php?topic=2626.0

 ReubenH said:

Just an FYI guy's, don't touch the second BOV by the secondary! It's not not a BOV in the traditional sense, it's got to do with the whole sequential TT system.

Technical ****e; i may be getting this a little wrong, please correct me rather than flame me if i have gotten it wrong.

During the secondary pre spool fase, it lets air circulate back to the intake. So you have the exhaust valve open slightly, the secondary turbo spooling up, and the intercooler valve CLOSED, and the second little BOV in there is letting all of the air the secondary turbo bumps back into the intake while it spools up. It closes when the the intercooler valve opens, and does NOT operate when you change gear. You'll mess **** up if you touch it.

If i remember right, this is probably the source of the noise we all refer to as george. The second BOV doing weird **** when close to vod.

Oh, yeah, the BOV off the intercooler by the primary turbo though is a completely normal one, and you can do whatever you want with it. Including flipping, or replacing with an atmosphere one.

[Guest]

In response to the quote from ReubenH - are you suggesting that the secondary bov is the sole cause of george? To me this makes sense, not for technical reasons but my 97 rsb was quite bad and a primary aftermarket bov change made no difference whatsoever..

So if one was wanting to eliminate George, they could replace the secondary bov with an aftermarket (NON-VENTING) bov?

[Koom]

 cadelac said:

In response to the quote from ReubenH - are you suggesting that the secondary bov is the sole cause of george? To me this makes sense, not for technical reasons but my 97 rsb was quite bad and a primary aftermarket bov change made no difference whatsoever..

So if one was wanting to eliminate George, they could replace the secondary bov with an aftermarket (NON-VENTING) bov?

George is caused by the factory 19mm BOV's being badly designed and "George" occurs when the rubber seal on the piston comes loose, this can also cause the BOV to leak. Easily fixed by gluing the rubber seal back onto the piston or just swapping the BOV for another known good one.

George can occur in either BOV and also can be found on some early single turbo Subaru's except it is much harder to create the same conditions where it can be heard often on the singles. It happens when the BOV is cracked open a slight amount, releasing the hold on the now loose seal and letting it "flutter" in between the piston and the sealing face.

[Guest]

Therefore replacing or fixing the faulty bov will result in the pressure being held in and getting more sustained boost levels? As the pressure would be getting lost at the most crucial time (heavy load on primary and spooling of the secondary - in this case). Or is it just one of those things to be left and admired, as I have no problems with George but if there is a benefit to repairing the bov I definitely will..

[Koom]

 cadelac said:

Therefore replacing or fixing the faulty bov will result in the pressure being held in and getting more sustained boost levels? As the pressure would be getting lost at the most crucial time (heavy load on primary and spooling of the secondary - in this case). Or is it just one of those things to be left and admired, as I have no problems with George but if there is a benefit to repairing the bov I definitely will..

Its usually the BOV that vents its air back to feed the other turbo isn't it? If its that one, its happening when the BOV is recirculating the air within the system rather than the one that vents back to the intake pre-turbo. So the loss isn't major as George is happening when the BOV is opening anyway. Its only when the seal drops back and doesn't allow the piston to seal properly that its causing "minor" issues for the system.

Its always good to fix broken stuff anyway.

[ReubenH]

 cadelac said:

In response to the quote from ReubenH - are you suggesting that the secondary bov is the sole cause of george?

Nope, was just speculation

And, er, what koom said.