Subaru WRX Forum banner

"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





 
#11,886 ·
People are telling you that you could compromise your cars reliability and performance by not setting a valve to recirc and you're still just worried about how it's going to sound? Sell your car. Buy a Honda.
 
#11,890 ·
Sweet, well, as you've probably already realized. Subarus are a really different machine. Lots to learn about them! Be sure to go through the stickies here on the forum, and you'll have a pretty good grasp on them! You won't gain anything from a blow off valve with them. An intake and tune will net you a little gain, though!

Edit: Didn't see your other mods before I made that post. Sounds like you're at a pretty good level. May want to look into an upgraded intercooler and fuel pump for your next mods. ETS Top Mount and DW65c would be two great options.
 
#11,896 ·
Keep the valve, just keep it recirculating.
My valve never leaked, others do after about 18 psi I've heard....the stock intercooler fails at that as well...mine did at stage 1 levels and split the end tanks apart

Sent from my SCH-I545 using Tapatalk
 
#11,898 ·
Probably depending on the severity. What other mods? Any exhaust work?
What's the valve set at?



Edit:disregard the above, didn't recognize your username. Yeah, more than likely normal. With just my catback I noticed some popping

Sent from my SCH-I545 using Tapatalk
 
#11,899 ·
As long as you've left it on full recirculation, your tune shouldn't need tweaked for the mod dark.

HOWEVER, if the old valve was leaking (and tuned for it) and now the new valve ISNT leaking, it may not need as much fuel as the old tune was giving it... leading to the rich "pop"

another possibility is that you've left the small tube coming from the BPV loose, or something.
 
#11,900 ·
I'm thinking about the Go Fast Bits TMS BOV. Right now my '15 STI's bone stock under the hood. Should the BOV be something to go along with other mods or is it good as a stand-alone tweak?
 
#11,904 ·
#11,908 ·
The question was whether a Subie {sic} will gain or lose power. The answer you're discussing was "yes." I don't interpret this as a recommendation any more than, say, "no."

Cantona got it right.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top