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"The BIG BOV thread" (Where all bov question threads get merged)

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#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





 
#1,128 ·
#1,129 ·
Just installed GFB BOV & MBC

Just installed my GFB Bov at 100% yesterday and it works good and no rough idle or anything.

I have 1 question though, when i dont boost hard, only like .03 or .04mpa and i let up off the gas i hear a fluttering sound, is that my wastegate, and is it okay?


I also installed my MBC, and set it for just a hair past .1mpa in 3rd, 4th, 5th gears.. Guessin around 14.7psi. I also used the zip ties onto the tubes, those tubes are gonna shoot off the wastegate and the turbo from the pressure are they.. Are those zip ties good enough to hold them on.

My car is bascially stock except for these 2 mods i just did and the intake silencer is removed, do you think that is a good boost setting to be on?
 
#1,135 ·
RexMobbin' said:
obcessed, its been 5 days since your last post, how's it working out? and how does one go about "reflshing" the ecu?
it still hasn't come yet :mad: ...

they lost the P.O. in the warehouse,....it should be here monday or tuesday though...i'll keep you informed...

as far as reflashing the ECU...it is ECUtek...you can get some info in the engine management forum on it...lots of stuff there..
 
#1,137 ·
Describe the sound a little better. If it's what I think it is, it is just when you don't build enough boost to overcome the BOV and it's the existing pressure exiting the stock air box. It's kinda like a turbo "fart" I can't really describe the sound, but it's a very fast on-off type pressure realease sound.

Later,
Eric
 
#1,139 ·
like i said in my posts on the linked thread, I have the forge and i am completely happy with it. It is loud enough to be heard, but not too loud. The car runs EXACTLY like it did stock, if not a teeny bit better inbetween shifts.

I had the turboXS- RFL before. It ran terribly, Stumbled at idle, ran rich, and hesitated while running. It was WAY Loud!

you will be happy with the forge 100 percent. IT has a dual valve system. it makes it work very well.
 
#1,142 ·
i think you'll have the same problem with the type-h as the RFL. They are a single valve, push type. so they will have a tendancy to leak unless you jack up the spring pressure so high that it doesn't release air until you really get on the gas., trust me , i had the rfl, i know.
 
#1,145 ·
The 100% Forge that I have does not flutter.
Another point that should be made about the Forge is that they are a completely rebuildable item and Forge supports with all spares. I needed to get the 'blue' as opposed to the 'yellow' spring and they sent if for free in 3 days from their US distributor.

Very happy with it!

Another point to note - it is a lot smaller that some other BOVs
 
#1,147 ·
The colour is the way they differentiate the 'stiffness' of the spring. I found it was opening venting too easily for my tastes and called them - they said 'no worries' you need a stronger spring - call George at Forge Motorsports USA and he sent it to me the next day.

To clarify the venting issue I had - I do not like the BOVs that open when you are in neutral and rev to 3000 rpm and open when you release the throttle - that is where a lot of the problems occur (IMHO).

I get slight venting in neutral only if I rev over about 5500 rpm.

I good exercise when you get your BOV is to take it apart and understand HOW it works.

THere are two springs in the Forge - If I get the urge this weekend - I may pull mine off and photograph the insides and post here - although it is Mardi Gras this weekend, I may be too distracted by all the beads and titty action!!


Cheers,

Andrew
 
#1,148 ·
hahahahah....

thanks aussie...

i should be receiving my forge either today or tomorrow so i will be sure to take it apart (no special tools required is there?) and then install it to see how i like it...

i agree i probably don't want the thing going off at 3000 rpm...more like the way you have it set up....in the 5000 rpm range...
 
#1,151 ·
aussieinstlouis said:


I good exercise when you get your BOV is to take it apart and understand HOW it works.

THere are two springs in the Forge - If I get the urge this weekend - I may pull mine off and photograph the insides and post here - although it is Mardi Gras this weekend, I may be too distracted by all the beads and titty action!!


Cheers,

Andrew
I undertook this disassembly when I had my GFB BOV. So I took some pictures for this very occasion. And for those that want to know how a BOV works. And the Forge BOV is probably very similar.

Enjoy<



 
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