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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





 
#7,577 ·
05wrx4U2nv said:
i got a vf34 660injectors tunede and i tried to put my stocker back on and when i shift i makes a bubble noise.it sounds like farting in the bathtub!is 18psi to much for it??it doesnt make that noise with a bov?dont mean to hijack but sounds like a good place to ask. thanks
There is a couple of mods you can do to the stocker to get it to hold more boost.You can cruch the top alittle in a vise (DSM method) or you can do this one
 
#7,578 ·
actually when i first came here I read a few threads and found the people just like him getting flamed for "stupid questions" and i decided to take a few weeks and just read stuff...and search common threads out....people comment on things like that because they are tired of telling people to use the search tool. :/

I usually try and help everyone to the best of my knowledge but thats just me :x
 
#7,579 ·
rallyrab said:
i was very upset with myself after i found this site, im sorry to say but the first 2 mods to my car were a txs bov and a k&n cai, i know, im happy to say though, since after finding this site, i have happily taken both of these off my car, i would just like to take the time right now to influence others to not buy a bov for their wrx, i immediately felt a difference in idle and shift smoothness once removed, not to mention i wasnt backfiring after every shift, so if u were thinking of buying a bov, DON'T, instead put the money towards a nice tbe or maybe an ap, trust someone who has already had one, that wonderful noise does get old after a while
+1
 
#7,581 ·
WRXSleeper said:
This post should be stickied for all the newbs or link into some FAQ thread. I too learned about not doing BOVs and intakes here before I even purchased my WRX. Coming from the honda world and having a friend with a GST who knew that stuff was bad for a WRX.
How about - they need to retype the first entry before they are allowed to post?
 
#7,582 ·
05wrx4U2nv said:
i got a vf34 660injectors tunede and i tried to put my stocker back on and when i shift i makes a bubble noise.it sounds like farting in the bathtub!is 18psi to much for it??it doesnt make that noise with a bov?dont mean to hijack but sounds like a good place to ask. thanks
FWIW - my vf34 runs 17.5 but was spiking up to 20 for a while due to the wrong restrictor pill (had kept the one from the vf34, needed the one from the stocker), I never heard any noise that sounded like what you are describing.
 
#7,584 ·
Help w/ Greddy Type S BOV..

Bought this car and my Greddy Type S is Recirculated, I wanna keep this BOV but I want it atmospheric..I Disconnected the Recirculate Pipe from the BOV but Im still not getting that "whistle" noise from my BOV, I've tried adjusting it, Do I need to cap off the Recirulated Pipe once disconnected from the BOV?..

 
#7,587 ·
ya you have to cap off that pipe, or just take it out and cap the hose... your car is probably running like crap right now if you didnt cap it
 
#7,588 ·
ya you have to cap off that pipe, or just take it out and cap the hose... your car is probably running like crap if running at all, right now if you didnt cap it
 
#7,590 ·
do you know everything that is done to that car? I can see that your running a cai and no heat shield on your turbo, hopefully it was protuned. You have to plug the recirculating pipe or your car will probably run lean because its ingesting more air than the maf is metering
 
#7,591 ·
Now Im confused as all #$#$! I have no idea, because there are no solid replies to yes or no when a bov should be used. Maybe that is because most Bov threads include a question about the first mod. I have read over and over about bov not a good first mod, Ok, Im fine with that, don't want one any ways.

But, what about after you upgrade the entire fuel system,get a bigger turbo (looking at 18G), get a FMIC, some engine management, and a dyno tune all at once. Is that an ok time for a BOV? Or is it after the boost gets turned up.

I have searched this, and everytime the question of an upgrade consisting of a bigger turbo/IC/Fuel system/dyno tune/EM, the replies are 50/50. I can't figure out what is the right solution.

Sorry not meant to Hi-jack, but maybe some good replies to this will help out future new suby owners with a question.
 
#7,593 · (Edited)
BoostedXTC said:
Now Im confused as all #$#$! I have no idea, because there are no solid replies to yes or no when a bov should be used. Maybe that is because most Bov threads include a question about the first mod. I have read over and over about bov not a good first mod, Ok, Im fine with that, don't want one any ways.

But, what about after you upgrade the entire fuel system,get a bigger turbo (looking at 18G), get a FMIC, some engine management, and a dyno tune all at once. Is that an ok time for a BOV? Or is it after the boost gets turned up.

I have searched this, and everytime the question of an upgrade consisting of a bigger turbo/IC/Fuel system/dyno tune/EM, the replies are 50/50. I can't figure out what is the right solution.

Sorry not meant to Hi-jack, but maybe some good replies to this will help out future new suby owners with a question.
The simple answer is, if you upgrade your turbo and begin running a higher boost level than what your stock recirculating valve can handle, you simply get a stronger aftermarket recirculating valve that can handle the increased boost pressure. There are stronger recirculating valves out there ya know, so just because all aftermarket BOVs can handle a good amount of boost doesn't mean that they are your only choice once you've exceeded the capability of your stock bypass valve. The only reason why these BOVs can be set to handle a large amount of pressure is because they're typically built to be more universal in their application, rather than for specific vehicle or motor.

With that in mind, just because you get an 18G, intercooler, fuel system, dyno tune/engine management doesn't mean that it is now OK to get a BOV. The basic operation of the system isn't really changing when you do such upgrades, you're just operating on a larger scale (bigger injectors and more fuel, bigger turbo and more air) than before, nothing more.

To sum it up, more boost does not justify the purchase of a BOV. More boost justifies the purchase of a better recirculation valve.
 
#7,594 ·
i believe Prodrive makes a replacement boost control unit, so does perrin - does anyone know if either of these units are plug-and-play
 
#7,596 ·
cheeseybacon said:
Erm, wrong thread maybe? Boost control units and BOVs perform completely different jobs.
Brainfart - my bad. stock recirc is considered good up to 25psi I think from what I've read on the forum. - I guess the question I was trying to ask is :

Are there any aftermarket replacements for the stock BPV which we can put a link to in this thread so that people can be referred here the next time the question arises?

(and the award nominees for run on sentances are.........)
 
#7,598 ·
JSCspeed said:
Perrin has recirculating BOV


Turbo XS also has an upgraded recirculating BOV the WS-RBV. We just got them in and they are very nice.
Now in order for these to function correctly and not cause the car to lean out - 100% would need to be recirculated correct?
 
#7,600 ·
i have the turbosmart dual port 50/50 and i could not be happier. yes, it it true that is dropped my mpg by 1 or 2 and it had 0 performance gains, but i enjoy the swoosh it makes and that was why i bought it. not to put in others faces, but for ME to enjoy when i and whipping through turns. it adds to the sensation of speed and power at a time when i am not vary fast at all. truth be told, once i get faster, then it is going to come off the car. i will have more than enough sensory input to know i am haulin' azz.
 
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