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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





 
#1,427 ·
Well, I just got mine!! I am just interested in the theory behind changing the springs and what the process is like and what to look for when taking it out for a test drive. Which spring for which power level, etc....

-joe
 
#1,428 ·
I use the blue spring. It is extremely easy to change them and the washers/shims are equally simple. Forge do give GREAT customer support.

One twist of the body and you can access the spring.

I wouldn't describe what I had as a stumble - it would not make boost beyond 4psi as the BOV was opening! Changed the spring and no probs - if you go too stiff on the spring you will not vent and get compressor stall.

You essentially have to match your spring tension to the boost levels you are running.
 
#1,429 ·
Thanks, I think I got it now. The guy I am getting mine from basically had the same mods as me and he said he had the medium spring installed in it. I am sure I will get a better feel for it when I get it installed and take it out for spin.

-joe
 
#1,430 ·
I just installed mine today, and I CAN notice some differences...

Shifting is a LITTLE, not very noticable at all, sloppy.

Sometimes the RPMs will bump up like 100-200RPMs when I'm shifting (after I let off the clutch)...

No big deals tho, but it's definately worth it! BTW, I got a Forge. :D

Now, tonite I need to install my MBC that I got in the mail today! Today was a great day! Forge BOV and MBC came in the mail, not to mention how beautiful it is outside. :cool:
 
#1,436 ·
you will have to also have to factor in sales and import tax in with the forge if you order it from the UK...

note the fine print...

Prices do not include shipping. You will be contacted to confirm shipping cost BEFORE your card is charged. If you have any questions or concerns please call FORGE on 01452 380999
it will probably be closer to $175
 
#1,437 ·
Note, I ordered from Forge's website (and it looked like everything was coming from the UK) - but Forge USA (in Florida) sent me my valve with no outrageous shipping charges. Loved the whole experience!
 
#1,439 ·
that's what i was gonna say about the forge company
it's not on UK, it's the one on the US Florida
sorry forgot to tell u that
 
#1,440 ·
is2scooby said:
Note, I ordered from Forge's website (and it looked like everything was coming from the UK) - but Forge USA (in Florida) sent me my valve with no outrageous shipping charges. Loved the whole experience!

do u no how long it took to ship to u

i just got done ordering my BOV striate from forge and the only charred me 150 because this is where it coming from Forge Motorsport Inc.
6536 Pinecastle Blvd
Suite 'C'
Orlando
FL 32809
USA
P.S thanks for all the help
 
#1,446 · (Edited)
EDIT: Before I start worrying about getting a new spring (the medium one is currently in there: blue), should I just let the spring break in? I mean, the BOV is brand new, and it's been only for two days. The reason I'm worried is because when in boost, it seems to be a little jittery...i think....i also had 6 ppl in the car! :)

P.S.: It was senior scavenger hunt!
 
#1,447 ·
Yes give the spring some time to break in. You might also want to lube up the piston a little better. I noticed that as the valve blows off it blows the lube out as well. I used a little general purpose grease, but I have heard of people using a dab of oil or WD40 or similar lube.

I currently have the medium (blue) spring in, and now that it is no longer winter the BOV is working great. I think the colder temps (near freezing) have an adverse affect on the BOV's lubrication.
 
#1,448 ·
i did notice that after putting about 50 miles or so on the bov the fluttering went away and i haven't had a problem since...everything is running great...

definitely give it some time to break in...
 
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