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

2M views 12K replies 2K participants last post by  WRX-maniac 
#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





 
#2,528 ·
KurleeDaddeeWRX said:
So did you get it installed or not? I don't just post and try to help out for nothing. Please post how your install turned out, and did you figure out your o-ring problem?
yeah, i installed it just fine. Your advice helped, the O-ring fits around the return piece real snug. It went fine.
 
#2,531 ·
OEM BOV sufficient for Cobb stage 2?

I plan to use my OEM BOV for Cobb's stage 2. Will the OEM be able to hold the increased boost. Will it still perform well?
 
#2,537 ·
AjIsDope said:
You can do that but I wouldn't risk it. I would just opt for an aftermarket one at that point.
well I think I'm going to top out at 16.5 or so. I love the smoothness of the OEM compared to aftermarket. That and I need to money for a stealthback :)
 
#2,539 ·
Well DSM guys have bene doing it for a while with no problems that I know of(hd a 99 GS-T a while back the a 00 Eclipse GT)

PLus if you get a big exhaust system you can hear the BOV quite nicely
 
#2,541 ·
I had an aftermarket bov on my stage 2 & 4 and then I went back to my stock and it worked much better. I noticed a huge diff. in response in between shifts. I had the txs rfl. I would keep the stocker until you change the intercooler to a fmic....
 
#2,543 ·
BOV...Silencer..

My Greddy Type S BOV is on the way. Right now i have my intake silencer out. If my BOV is set to 100% atmospheric, will it be louder with the intake silencer in or out...or no differnce. I know if i set it to recirc. then it will be louder with the intake silencer off. But what about on 100% atmos??.. thanks!
 
#2,546 ·
I have a somewhat related question.

I am a newbie to WRX's and I hear a lot of talk about BOVs.

Does upgrading to an aftermarket BOV do anything for performance or is it just a sound thing? I understand that if you are running higher boost then you should go to an aftermarket BOV but does it do anything on a stock application? Thanks for the help.
 
#2,548 ·
well when I had mine you can notice the difference withthe stock BOV and the revs going up between shifts, that dont happen with an aftermarket
 
#2,549 ·
'04 Bov?

Just wondering....

I kind of know what BOV is now, and what it does. My rex has
4500 miles on it. Here is my question....is it worth it to buy a BOV
for my car? and will it void the warranty in any way? I know about
dealerships saying it has to be directly related to the cause of a
problem....BUT, should I get one to help my turbo last (and the cool whoosh sound)????...and just
remove it if I get problems and need to go in? Also, where exactly
does the BOV go? Thanks.
 
#2,550 ·
Re: '04 Bov?

r0xz0rz said:
Just wondering....

I kind of know what BOV is now, and what it does. My rex has
4500 miles on it. Here is my question....is it worth it to buy a BOV
for my car? and will it void the warranty in any way? I know about
dealerships saying it has to be directly related to the cause of a
problem....BUT, should I get one to help my turbo last (and the cool whoosh sound)????...and just
remove it if I get problems and need to go in? Also, where exactly
does the BOV go? Thanks.
Not worth getting it until you get over 20 lbs of boost.

It MAY void your warranty, probably not though.

You can take it off in 5 minutes, and put on the old one if you have to go in for service.

The BOV goes on the TMIC. You can either get 100 % atmospheric and plug the BOV return hose, or get an aftermarket recirculative BOV.
 
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