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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





 
#7,554 ·
I actually didn't buy them myself...my kind brother picked them up cause I had mentioned to him a week ago that i was trying to decide what to do. I had changed my mind about the upgrade since you all gave me the great advice. I hope i didn't offend any of you, i really do appreciate all of your kind advice and helpful guidence. Thank you all...really!
 
#7,555 ·
whitakerSTi said:
negative, the APS 50/50 recirc valve is the absolute best aftermarket bov hybrid on the market. It recircs 50 percent into the system again and blows off 50 percent to atmosphere...its the safest for our cars due to this. You can get this part from rallysportdirect.com or pretty much any tuner site dedicated to subarus.

Its also completly tune friendly...it doesnt have to be 50/50...i believe you can make it any ratio you want...60/40 perhaps...depends on your setup and needs.
I am thinking of eventually getting the VF34 Turbo kit and I am wondering if this APS 50/50 will still be ok. Do i really need a BOV? Isn't the stock one good enough for the small boost upgrade? Oh, and what is an ssqv..or something
 
#7,556 ·
Poekin said:
did anyone else read the title and say to themselves "O man this poor kid"
+765876969860879 :rotfl: :rotfl: :rotfl: :rotfl:
 
#7,557 ·
sorry bro but you need to listen to the people that are talking to you in this thread


1. Search and you will find

2. Notice how EVERYONE is telling you that the STOCK BPV will work to 20PSi.

3. APS will be fine with a tune and big turbo, if you decide to go over 20 psi


IBTL



i think we need a
 
#7,561 ·
Touge Daimao said:
I am thinking of eventually getting the VF34 Turbo kit and I am wondering if this APS 50/50 will still be ok. Do i really need a BOV? Isn't the stock one good enough for the small boost upgrade? Oh, and what is an ssqv..or something
as said earlier...stock bpv is good to 20 some psi....when you start hitting 20G levels or superzillas...or garrett turbos...then think about the APS unit. But if you have a VF-34 in mind then i doubt youll use the potential of the APS unit...so just stay stock
 
#7,563 ·
Touge Daimao said:
I actually didn't buy them myself...my kind brother picked them up cause I had mentioned to him a week ago that i was trying to decide what to do. I had changed my mind about the upgrade since you all gave me the great advice. I hope i didn't offend any of you, i really do appreciate all of your kind advice and helpful guidence. Thank you all...really!
It's no problem, and you're not offending! We just want to help you so you don't run into any problems with your WRX down the road. I know we threw a lot of info at you, so it may take a bit to let it sink in. :thumbup:

Oh, and it was nice of your bro to buy you a BOV, but you can sell it on ebay and buy a catless uppipe...you'll be happier! ;)
 
#7,564 ·
okie, ummm, i'm not too familiar with the suby exhaust system...i know there is a downpipe and cats...what is the uppipe? will this conflict with emissions regulations? WHile we're on this topic, what should i avoid tinkering with in order to keep upgrading but not get snagged by emissions?
 
#7,565 ·
Touge Daimao said:
okie, ummm, i'm not too familiar with the suby exhaust system...i know there is a downpipe and cats...what is the uppipe? will this conflict with emissions regulations? WHile we're on this topic, what should i avoid tinkering with in order to keep upgrading but not get snagged by emissions?
What year is your car?
 
#7,566 ·
Touge Daimao said:
okie, ummm, i'm not too familiar with the suby exhaust system...i know there is a downpipe and cats...what is the uppipe? will this conflict with emissions regulations? WHile we're on this topic, what should i avoid tinkering with in order to keep upgrading but not get snagged by emissions?
The uppipe is what feeds your exhaust to the turbo - take a look below.


On 2002-2005 WRX, the uppipe contains a cat, this creates restriction (it also serves the purpose of creating a cleaner exhaust... but we don't care about that - we want POWA!), which we can eliminate by installing an aftermarket piece, or by "gutting" the stocker. This change will improve turbo spooling by a few hundred rpm, and is generally considered a good first mod. There are still two more cats in place in the stock exhaust system, but yes, from a legal standpoint, you are degrading the performance of the emissions system.

Check your local laws. In most areas - the law says that you can't touch the factory exhaust at all. However, you can usually get away with one highflow cat. If your inspection involves the OBDII port, then you will need "Ready" status on all your monitors. You may wish to look into MIL or CEL eliminators.

You probably have more questions now than you did before. Don't let that discourage you. Keep asking questions, and people will keep telling you to search. It's all part of the process of learning when you are on a forum. Eventually you will learn to search before posting.
 
#7,569 ·
oh, and the reason you want to avoid putting a BOV on your WRX is because of the MAF system used by our vehicles. The MAF will read air passing, and add fuel, the BOV will let this air out, but the fuel will still go in. Now you've got way too much fuel(or not enough air), that will result in running extremely rich. When this happens, typically all of the fuel is not burned in the cobustion process and unused fuel is present in the exhaust. This causes a condition called "cylinder wash" where the fuel hits oiled parts and displaces the oil leading to an increase in friction and also heat. This can affect many things(I am not a mechanic, merely a car enthusiast - so I am not the ultimate authority on this, but I have been told the same thing by many differint mechanics) - two of which are rings being underlubricated from lack of oil, and also increased oil consumption.
 
#7,570 ·
juanes287 said:
Buy the biggest possible BOV you can find. The bigger the BOV the more hp you will pick up. Then you should procede to make a gigantic pipe from the bov and angle it up through the hood of the car.
The first three comments were all the guy needed.....He is new and doesnt know and hes not a ricer so i dont understand the reason for the sarcasm and rudness......So were you born knowing that BOV's are bad for subies....I figure you found out in July, right?

this site pisses me off sometimes
 
#7,571 ·
listen to bov bashing

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



oh and i have a txs type h bov with adapter kit for sale if anyones interested:thumbup:
 
#7,574 ·
So nice to hear, and it's nice to see a BOV thread that doesn't ask WHY they are bad :thumbup: . I did the same thing but only had the BOV on my car for about 2 days, couldn't stand the noise...not to mention my gas mileage was worse with it installed and there is NO need to have the "hey look at me, IVE GOT A TURBO" attitude....people know, no need to jam it in their face.
 
#7,575 ·
REXtard04 said:
So nice to hear, and it's nice to see a BOV thread that doesn't ask WHY they are bad :thumbup: . I did the same thing but only had the BOV on my car for about 2 days, couldn't stand the noise...not to mention my gas mileage was worse with it installed and there is NO need to have the "hey look at me, IVE GOT A TURBO" attitude....people know, no need to jam it in their face.
+ 1
 
#7,576 ·
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
 
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