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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





 
#2,552 ·
open up your whoel system and you 'll hear it just fine, I got TXS pod filter MRT inlet and upipe back and i can even hear it over my loud ass BPM exhaust
 
#2,554 · (Edited)
BOV yes or no - please comment

I am thinking of Installing a BOV (HKS) in my wife's car. Mostly for the sound. After reading several postings, i am getting confused. If you had one installed in your car and you removed it, what was the reason that made you go back to the stock. If you currently have one installed, I wouldlove to hear your comments....

After kit that was suggested to me was by a company called TurboSmart...has anyone heard of them?


Can I expect an improvement in engine response?


Thank you
 
#2,555 ·
alot of people tend to remove it after awhile because the BOV sound gets to them over time.. at first its cool but then hear it over and over for a year or so.. ull want to change..
but if you like the sound.. dont worry about gettin annoyed or whatever and get it..cause its an easy install/uninstall
 
#2,556 ·
i had one and yes it did get annoying plus i dont like the attention it ads to my car (its already loud enough). I realized the factory BOV is good for like 18 psi, so when i upgrade my turbo, i will get an after market 100% recirc.
 
#2,557 ·
If you're going to get one purely for the sound, get a used one like I did. A BOV will NOT help your performance, and may potentially hurt it if it's not recirculating like the stock BOV. The reason is because you'll run rich between shifts with the lack of air going into the intake system (that's dumped with the reciruclation of the stock BOV). There are aftermarket recirculating BOVs out there, but they're not very loud, so there's no point in getting them if you just want the sound.

To me, there's just nothing like rolling next to some guy that thinks he's badass with a gawdy looking car and just letting off the throttle as you pull up next to his rolled down window....PSSSSSH...WHAT NOW??? :D
 
#2,560 ·
What does your wife think?

A local WRX has a TurboSmart Supersonic which doesn't sound bad at all. No problems AFAIK.

Chances are most WRX owners will upgrade their turbo, at which point an aftermarket BOV will likely be required. So there's really no hurry in getting one while running the stock turbo.
 
#2,563 ·
I put a turboxs BOV on my car, and took it off after one week. The sound got old awfully quickly, and I had all the problems others have brought up. Throttle response was bad, stumbled a bit at low engine speeds, wouldn't start a few times. It did get better after reseting the ECU and doing the quick learn, but it still didn't run as well as stock.
 
#2,566 ·
I have had my TurboXS RFL on for the past 10,000 miles (since 5k) and I still like the sound. I do think its a little too loud though... Anyway, I have always noticed a ever-so-slight decrease in performance, like others, running rich, stumbling, shuddering at low rpm's.... I wish I could have the sound w/o all the bull$h!t but what am I gonna do? I wanna take it off but I'm so used to having it on for so long! It's kinda like removing that 15 pound tumor you've had on your face your whole life.....no wait, not really....:confused1
 
#2,567 ·
I've got a fully adjustable, spring perch worxtuning recirculating BOV which is absolutely gorgeous (wrinkle red or blue finish with polished aluminum/ss.). Never had a problem with it, no stuttering, rough idle, etc. Great thing about it is I can adjust it easily so reduce the noise by recircing more air back to the compressor.

It's distinct in sound, but not "look at me" loud. To me, it's the perfect balance between announcing to those that know...yep, it's a turbo" and to those that don't you won't be startling old ladies into dropping their shopping bags.

Check em out. I highly recommend their service!!!
www.worxtuning.com
 
#2,568 ·
I am running a Worx BOV as well, its been great! They are in development of a new adjustment ring that will make it louder. This particular BOV is awesome because you just turn the adjustment ring and you can go from 100% recirc to various levels of sound/vent.

I tried the HKS once and it made my car run like crap. You'll find peoples experience with the HKS varies quite a bit. My car felt like I was towing about 500lbs after shifting gears... definite and noticable performance degradation. The guy I sold it to reported his car ran fine with the thing....
 
#2,570 ·
Thank you for all the feedback.
Warranty is not a problem. Subaru will install it for me (this way ensuring the warranty remains). The wife wants the sound. My only concern was with loss of power...from what I read here, it's hit and miss. Making my decision that much more difficult.

Veteq
 
#2,571 · (Edited)
Typically the "Hit and miss" nature of an aftermarket BOV is due to the factory MAF sensor.

On cars that use these sensors they are placed before the turbo, but the BOV vents into the intake after the sensor, so to make it easy to understand: If you have 10cfm of air going in, your MAF reads that and adds fuel for 10cfm, car works like normal, any air trapped before the TB when you shift is "recirculated" back into the intake stream and your stock car runs nice and fine :)

If you have an Aftermarket BOV, you suck in 10cfm of air like normal, when you shift 5cfm gets dumped to the atmosphere (that makes the psss sound) but your engine has already added fuel for 10cfm... so your running super rich, that is what causes the stutter stumble effects, especially while shifting. Aftermarker recirculating valves dont typically have this problem since they function like stock.

Ways around it, stand alone EMS, or things like an HKS VPC (Vein pressure converter) that measure air differently and later in the intake stream, instead of a "flapper" door style that measure air before the turbo(I believe that is what you have on your cars.) These measuring tools typically measure later in the intake stream (closer to the TB) and so it doesnt matter if you dump all but 1 cfm of air since it will only read 1cfm is going in the engine, :)

FYI the HKS BOV is a very good BOV especially if you vent it back into your intake stream since the pressure holds the BOV closed instead of pressing against a spring like most standard BOV's that, if you have a weak spring, can cause leaking... and since its operated by a vaccum it opens and closes VERY fast, which is why it typically does not cause a reaction as extreme as other aftermarket spring type BOV's when shifting since you dont run as rich for as long.

:)
 
#2,572 ·
BOV vent 100% or recirculate ? HELP

hello peeps .. heres a dumb question you probably heard over and over.

i have a turbo xs BOV that vents 100% to the atmosphere.

im getting a greddy type s that can either vent 100% or the option of me attaching it so it circulates back into the intake.

what should i do ? vent 100% or recirculate.


whats the major difference besides noise ? ?

:wiggles:

engine mods ..

injen intake
colder sparkplugs
borla headers
hks uppipe
hks downpipe
blitz exhaust
apexi avcr @15.5psi
turbo xs tmic
turbo xs unichip
turbo xs bov
CO2 intercooler chiller
 
#2,573 ·
If the bov isnt on recirculate, you will be running a little rich between shifts because the computer is expecting the recirculated air (that the 100% atmosphere bov vents to the atmosphere) back into the intake stream. You wont feel any difference in performance (i didn't between the 2 modes) or see it in gas milege.
 
#2,575 ·
Is there a new one out? Because I have the one on Blitz's website and it's also called the DD...
 
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