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.
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.
i'm not sure about keeping the turbo spooled between shifts... i noticed much the opposite when using my stock bypass valve.
i'm using the hks bov right now. it works great, but i also have most of a full exhaust installed (catback hopefully coming next week). there seems to be a weird correlation between how well a bov vents and how little backpressure you have. i have no clue why
anyway... no stumble. rich condition? much less than a second. does it slow me down? nope. is it a big deal? hell no.
on my completely stock exhaust i liked the oem bypass valve better. with my current setup (pde up and down) i absolutely hate the bypass. if i had more cash to simply throw around i'd be tempted to try out the greddy seq. unit just for fun.
oh, and the hks can only be set up 100% atmos. or 100% recirc.
you realize if you seriously wanted to, you could have simply adjusted the hks tighter so it didn't blow off till more boost was made? although if i was your compressor wheel i'd probably hate you for not venting any and all positive manifold pressure between shifts
if you don't have any exhaust mods yet, i'd recommend holding off on buying a bov. get a little more oomph to back up the smack your bov will be talking.
that said.... with my hks i don't exactly use my horn as much, as my bov is a lot louder i think it's time to install my air horns again.
do you have the sound clip for GFB?
i always wanna buy that one, but i nobody has it here
so i'm always wondering how good is the sound
i'm not looking for a really loud one
I just noticed a slightly orangish-brown residue being vented from my Forge 100% BOV. Just wondering if anyone knew what it was? I figured it was some kind of assembly deposits in the intake tract being vented out, because I put the BOV on after only 800miles on the engine.
Thanks to everyone on this board whose posts I searched and mulled over night after night until I decided to get my Forge BOV!
Installed it this morning , very simple, and noticed no difference in how the car runs ( reffering to problems , that is) , but what a nice sound!Normal driving under 3k doesn't produce anything but get her into boost and there it is!
I dont have a sound clip of the GFB. I should make one though... cause before I bought it I searched EVERYWHERE and couldnt find one. It just sounds like a PSSSSHH noise... almost like something hydraulic (sp?). It is not all that loud but certainly audible both inside the car and out when it does blow off at full throttle. I passed a skate park the other day and was trying to get in front of another car and the thing blew off right in front of the place... I got a few cheears and some thumbs up. lol The car actually runs smoother with the GFB imo. I've already taken sh!t for that comment though, so dont bother. GFB claims it improves throttle response, etc and I cannt deny that.
I realize I could have messed with the HKS a bit, but the car ran SO badly with it, I didnt even bother. I was worried about getting a 100% ATM valve in the 1st place and went against my better judgement. I sold it to a dude on NASIOC who said it ran great on his car, so thats cool. The GFB running hybrid was perfect for my needs. I wanted the sound, but only sometimes... and I wanted one that wouldn't make the car run badly... I'll be doing more engine mods as soon as possible. I bought the car in August 02 and only have 2700 miles though.. so I was getting ansy. I've dropped like $5K on appearance and was running out of crap I wanted to buy, so went for the GFB. I'll be doing the rest of the exhaust soon, and other mods to follow. I was thinking about the APS RT Spec most recently. Cobb tuning is 15 minutes from my house.
chobits, I'll attach a scan of the front page of the document that came with the GFB... it explains some stuff about the valve, etc. For what its worth...
Thanks to everyone on this board whose posts I searched and mulled over night after night until I decided to get my Forge BOV!
Installed it this morning , very simple, and noticed no difference in how the car runs ( reffering to problems , that is) , but what a nice sound!Normal driving under 3k doesn't produce anything but get her into boost and there it is!
For one thing, the stock hoses, over time, will crack because of the high heat in the engine compartment. The Samco's won't crack. The Samco's also have a larger inner diameter, to flow more air. They are also made out of silicone, which is very smooth, and allows the air to glide through easier. And they also look good.
If you follow that thread above, you will see the stock black Y shaped hose that connects on the back of the intercooler. It is has a super small inner diameter. Now check out the blue Samco hose. See how much larger it looks. If you did a comparison and held each one up, you would really see the difference.
And the Samco's are supposedly good for a 8hp increase.
what kinda turbo do you have, cuz i've got the same bov, when the engines still a little cold, the thing is even louder, i made this woman jump i felt kinda bad cuz she grilled me hardcore afterwards lol oh well
Can someone who has the hks bov tell me exactly step by step what they did when installing it. I have my own but im not sure if i have it set up right. They give you an extra long tube plus alot of zip ties. Thanks!!!!!