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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





 
#7,633 ·
wait until your car is decently cool, so you dont burn yourself.

tools required: pair of pliers, and

First remove the vacuum hose that goes to the bov. its right in the front, towards you.
Then remove the bov via the two bolts on the mounting plate. i believe they're 14mm. be careful not to ruin the gasket.
See that big black hose with a metal plug in it right below the front of the intercooler and a hose clamp. loosen the hose clamp and remove the plug.
Mow take you stock bpv and in push the open metal pipe into the hose, and put the clamp on the bpv.
Then put the two bolts through the bpv and gasket and into the intercooler, and tighten.
Put the vacuum hose on the bpv, im not sure what the actual spot where it goes is called, but its the brass pipe.


now drive around and love the drivability.




i dont think i forgot anything, but if i did...
 
#7,634 ·
sounds about right
 
#7,635 ·
Turbo XS WS-RBV bypass valve for Big 16g?

I'm looking at upgrades for a 2002 WRX I'm workin on with a friend. So far engine wise we've decided on:

Big 16G or 18G w/ internal waste gate
Walboror 255lb fuel pump
New injectors
Engine Management (not sure whos yet)
Large TMIC
TBE- bell mouth DP
Up pipe
CO2 N-tercooler sprayer
Water Intercooler sprayer
Turbo Heat shield

Was wondering if this system would come close to maxing out the stock Bypass valve and warrant upgrading to a better one.

Note: Im planning on venting back into the intake. NOT venting to atmosphere
 
#7,637 ·
sounds good but only one thing to add to make it easier for you. If you take a look at the recircualtion hose, the black rubber one with the metal spring clamp. That metal clamp has a pair of teeth on it so you can lock it open. So you can slide the recirculation elbow into it, then bolt the BPV in place, then release the lock on the clamp so the hose aligned right.

The only other thing you may need to do is if your BOV is big like my Worx one was, the metal vent line that runs along the front of the intercooler may need to be moved. Its just 2 or 3 10mm bolts to take off and it will let you move it around if its in the way.

:thumbup: :thumbup: :thumbup: :thumbup:
 
#7,638 ·
If you're going the TMIC route, I'd stick w/the stocker. I actually have the re-circulating TXS H34 myself and it works great with my setup, but I would have just stayed stock if I hadn't switched to an FMIC.

That said, if you want a little bit more sound, you can use the TXS valve and won't give you any trouble.
 
#7,643 ·
The simple answer is no, you can't run a BOV and still make it 100% safe, no matter how you tune it.

The fact that you're venting air out of the intake tract and straight into the atmosphere, air that your ECU anticipated being there, means you're always going to run rich. If you MUST have some scream "oooh look at me everyone, I have a turbo!" whenever you shift, consider a Cobb SF or SPT intake instead. Neither will do much in the power department, but they will make your stock bypass valve louder which should satisfy your ricer tendencies without messing with your A/F ratios.
 
#7,644 ·
It's (not) simple - just convert your car from MAF to MAP - then create a custom tune.

Cobb AP + Protune/Streettuner
or UTEC or Enginuity - probably more ways to do it also.

Of course the only way you're going to get someone to help you with this - is probably paying them by the hour. It's a bad idea really - if you want the BOV sound that bad, just buy the electronic BOV noisemaker off e-bay - just as rice and it won't damage anything - well, other than your image
 
#7,646 ·
Newb question

Hello, im new here, ive been reading around the forums a bit and noticed alot of people say BOVs are bad. i plan on getting a wrx this summer. my understanding is that BOVs r required by turbos to release pressure so the wrx must have a BOV i want to know if the BOV makes a noticable sound and if not, how hard would it be to switch it out for one that is a little louder. i must have that "pshht" sound when i shift!
sorry if any of this dosent make sence, but i figured now is as good a time as any to start learning about these things
 
#7,653 ·
Hello, im new here, ive been reading around the forums a bit and noticed alot of people say BOVs are bad. i plan on getting a wrx this summer. my understanding is that BOVs r required by turbos to release pressure so the wrx must have a BOV i want to know if the BOV makes a noticable sound and if not, how hard would it be to switch it out for one that is a little louder. i must have that "pshht" sound when i shift!
sorry if any of this dosent make sence, but i figured now is as good a time as any to start learning about these things
Its pretty obviouse that you did not read anything. BOVs are bad and dumb. Go rice out some civic instead.
 
#7,647 · (Edited)
no.

if you really DID do some reading you already know you CAN'T get the sound you're looking for without installing something that will mess up your car. Subaru's already HAVE a valve, it just doesn't make any noise.

looks like you didn't like the answer you came up with by searching so you're asking again hoping to get a different answer. you won't. BOV's suck.

you should have bought a old DSM or a turbo'd Civic.

a n00b asks this question on this forum at least 3 times a day, and the answer is always the same.

just say "no" to BOV's.
 
#7,648 ·
Bov...

someone please correct me if i'm giving info out incorrectly. From what I've come to understand about blow off values is... they aren't bad for your car but they don't improve performance and that lovely darth vader sound is annoying (to some/not all); and hence most people find them pointless and talk negatively about them. I happen to agree with the masses on this one. I rather get better speakers in my car than have 9ussies anakin turn darth vader on me every time I shift.
 
#7,649 · (Edited)
someone please correct me if i'm giving info out incorrectly. From what I've come to understand about blow off values is... they aren't bad for your car but they don't improve performance and that lovely darth vader sound is annoying (to some/not all); and hence most people find them pointless and talk negatively about them. I happen to agree with the masses on this one. I rather get better speakers in my car than have 9ussies anakin turn darth vader on me every time I shift.
I guess YOU need to do a search too.

BOV's mess with your a/f ratio.

and yes, its also pointless and annoying.

"Hey...LOOK AT ME!!! I have teh trubo! I am teh fast4R"

meh.
 
#7,651 ·
in all honestly... i should do a search...

thank you... i swear I'm been reading on here like crazy; i've been written up at work already cause i'll ignore customer customer because i'm on here reading. I probably just missed that part about the flow being messed up. Thank you though for the correction. My friend was argueing with me about putting a BOV on my car. I said no he says yes; but he drives civics and such.
 
#7,663 ·
i was wondering about price...

my first question i asked was about price on a used wrx... it was to speedette i remember cause she be a hottie! haha. I went brand new though... 15K for a used 2002 with mods that were put back to stock and no history on any of the services done to the car... plus the guy didn't know his front end was repainted... no bueno at all. Sorry about being off topic.
 
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