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"The BIG BOV thread" (Where all bov question threads get merged)

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#1 · (Edited by Moderator)
This is the big BOV thread. If you didn't find this thread, you didn't search.

This thread is where all BOV question threads get merged into.

The quote below in this first post is from our BOV info sticky and contains links to some very explanatory BOV information. Please take the time to explore the links before you ask repeated questions.

Thanks!


A stock WRX/STi comes with a BPV (Bypass valve) which is a vacuum-actuated valve designed to release pressure in the intake system when the throttle is lifted or closed. This air pressure is re-circulated back into the non-pressurized end of the intake before the turbo.

An after market blowoff valve (VTA) does basically the same thing BUT unlike the stock unit it releases air to the atmosphere (giving you the loud sound). Some people see an after market BOV on a stock WRX as being in poor taste (probably due to the fact that it is basically a noise maker that really as no other benefit), while others simply find the sound very attractive.

Proponent opinions notwithstanding, there is a small mechanical downside to having an after market BOV (VTA) on a stock WRX. The problem comes when releasing air to the atmosphere that has already been metered by the mass airflow sensor. When the BOV releases (blows off), the ECU will be injecting the wrong amount of fuel into the cylinders. The engine temporarily runs too rich (meaning too much fuel is injected into the cylinders). This temporary rich condition isn’t typically THAT harmful, but it may cause bucking or hesitation on lift-throttle as well as some other concerns outlined in the links below.


Links for BOV info:

Sinister's BOV FAQ

Wikipedia

Unabomber on Nasioc

Davenow on Nasioc





 
#2,652 ·
i have a turbo xs v2 tmic also i had a turbo xs bov but replaced it with the greddy type s --

big mistake.... it didnt fit and i called turbo xs and they said that turbo xs bovs should only go on the turboxs tmic ... i said screw it...

i made a flanged ( 2 hours of work) and it works fine no leaks...

from what your saying it does sound like a leak... do a water test
pour some water on the flange of the bov and see if its leaking..

if so tighten but not to tight cuz u dont wanna strip threads on the intercooler.

do u have a boost gauge.. ? ? ?

usually if you have a leak on 3rd and 4th you will get dips on ur boost... like from 15psi on full throttle and it slowly drops down while ur foot is still on the gas...
 
#2,653 ·
I have a blitz bov and have had it for about 3 months really the only difference that I have seen to my sti other than the sound of the turbo (which I really love ) is that the car burns rich I also have a turbo exhaust with no cat so I am not sure if burning rich is because of the exhaust and bov or just the bov
 
#2,658 ·
yeh, I have a gfb and turboxs top mount. The problem is the turboxs top mounts bov mount doesn't fit the bov correctly. When I got it, I had to grind part of the flange off my bov to get it to sit flat on the intercooler. On another note, my intercooler came with metal shavings inside it.......
 
#2,659 ·
for those having problems???
did you adjust the BOV???
according to HKS they are preset from the factory

heres what someone wrote on their forum:

Anthony,
Regardless of actual performance (good or bad), venting a blow off valve to atmosphere on any OE MAF car will cause a rich A/F condition when purging. As you mentioned, the OE configuration is recirculating. Also, the SSQV comes pre-adjusted from HKS intended for the specific vehicle. Often, users trying to adjust the SSQV do more harm than good.

Anyhow, here is my speculation on the other problems...

1.) Rich A/F: mentioned above
2.) Stalling: BOV is adjusted too loosely
3.) Turbo lag: there is a vacuum leak
 
#2,660 ·
20wrx02 said:
i have a turbo xs v2 tmic also i had a turbo xs bov but replaced it with the greddy type s --

big mistake.... it didnt fit and i called turbo xs and they said that turbo xs bovs should only go on the turboxs tmic ... i said screw it...

Thats a littel dis-heartening. I have a blitz on my v2 tmic, never had any problems. Other than its totally atmospheric and at very light throttle it kind of stutters.
 
#2,661 ·
First of all, I suggest you use BRAND NEW gaskets for both the BOV and the cast pieces on the back of the intercooler before you start trouble shooting your problem. It is very easy to get a leak with old gaskets. And too many people trust old gaskets. Re-assure yourself by using BRAND NEW gaskets.

I have the TXS ver. 1 TMIC, which supposedly had more problems for mounting aftermarket BOV's than the ver. 2. I run a Forge 100% re-circulating BOV with absolutely NO problems.
 
#2,662 ·
I have a TXS Ver2 TMIC with an APS recirc BOV and I had an issue getting the valve to sit properly. I tried to alleviate the problem by torquing down the bolts a little too hard and stripped the IC threads. I had to use longer bolts to catch threads all the way at the bottom. I ended up having to put the BOV on the IC out of the car, then putting it in.... biggest PITA ever! :mad:

Works great now though...
 
#2,663 ·
hey kurlee, I tried putting 3 gaskets on when it didn't fit cause I didn't wanna grind my bov. The tmic bov mount would not let my bov sit flat on it! I never even put the intercooler on til I grinded the bov cause I noticed it right when I got the intercooler and tried to get all the hosing to fit on correctly. This is not a gasket problem, it's cause txs only tests their intercoolers with their bovs(at least that would be my guess)..........

peace
 
#2,664 ·
installing turbo xs type h bov

I just bought this bov for my 04 wrx and I have a few questions for whom ever that can help me. What do I do the with black circle thing? What do I do with the spilter on the end of the tube ? Am I missing any gaskets? I bought the bov off ebay.

PLEASE HELP!!!!
 
#2,665 ·
Hi there,

First of all, that kit does look complete, so you're not missing anything. The stock gasket is pretty much attached to the intercooler and as long as you are careful when removing the stock BOV, it will not tear and is fully re-usable.

The black T-Connection at the end of the vacum line should only be used if you have a boost gauge installed. If you do, then you would put the T in-line between the new BOV and the stock bov vacum line. the Boost gauge line would then T-in there.

If you do not have a boost gauge installed, remove that whole line, and just plug the stock line onto the top of the BOV.

The "black circle" is actually a plug to the BOV return line that goes back to the intake. Since the Type-H does not recirculate, you will need t simply place this plug inside the return line.

Good luck,

Michael-
 
#2,667 ·
You can remove the black pipe completely if you want to, but you will have to find a cap for where it goes back to the intake, otherwise you'll have a hole in your intake pipe :)

Honestly, it's much easier to just go ahead and plug the pipe, until you get an aftermarket turbo-inlet hose at which point you can cap it no problem.

-Michael
 
#2,672 ·
STi BOV

Im looking to buy a new blow off valve for an STi. Im looking for a nice long pshhhh rather then a high pitched squeek. If anyone has information or possibly a sound bite i would b gratefull. thnx:wiggles:
 
#2,675 ·
god I hate those tweety laser-beam sounding ones:confused1

Im using the APS one that recirculates part of the air back, remember the MAF sensor has acounted for all that air and your computer still thinks its all heading into the engine! Nice thing about the APS one is its adjustable how much you want to hear the blow-off since it would drive me crazy if I heard it ALL the time, just when I get on it, and then it sounds like Darth Vader running a marathon!:D
 
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