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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





 
#2,602 ·
Re: Bov

reyneon said:
I recently bought a car with a BOV installed. When I took the car for a test drive I could hear the BOV. Now no matter how hard I push the car I don't hear any sound. What could the problem be?

What brand is the BOV? The pluger could be jammed, or maybe the hose fell off?
 
#2,604 ·
Aps Fmic Bov ?

I just got in the mail today my APS FMIC BOV. I bought it used from Mili, and have a question for anyone that has one. i see where the IC hose attaches to, but where does the intake return hose connect? it looks like there's 2 screw holes for a flange, and there was something attached here before (i can see the imprint, but there's nothing else in the box). What am i missing? anyone have a link to the part? thanks
 
#2,607 ·
WORX tuning BOV..

Hello you all,

Today I got my worx tuning BOV in, and installed it. Boy,did it take a long time. I know that a BOV only takes like half an hour, but my previous BOV was the TXS type RFL. What a big difference! The guys who worked on my car for my TXS FMIC cut the "BOV Hose"- the one that connect the BOV to the turbo inlet pipe- so it was exteremly short as to make the FMIC easy to install. So I had to get another one, then I practically had to take out everything to get the damn hose in. Shoot it took forever, then when I put the hose and IC pipes in, the BOV was about an inch off. So I bolted the BOV on the IC flange, then put it in like that. Everything is secure but I a little skeptical about the silicon hose-one by the throttle body that connect IC pipe to intake manifold- because it is very short and the IC pipe isn't in all the way. So I'm going to have to buy one with more height.

As I started it up, I took it out for a run and shoooot I have a lot more LAG~!! what is that all about? It lags hard then finally around 4000rpm it starts to move. The RFL didn't do this, can a BOV make this big a difference?

It says to break it in for 1000 miles- does this mean that I drive easy or can I drive normally with a few WOT runs here and there?

and Where is the adjustment bolts (5 bolt thing) located at?

And when I do get to 1000 miles- how do I take the BOV apart to clean the pistons and such??

thanks.
 
#2,611 ·
You want to use silicone grease for the swaybars. Sometimes auto parts stores sell it in small tubes labeled "dielectric grease" or "tune-up grease". I'm not sure I'd use vaseline on my car for anything. I guess it would be OK. Never occured to me before!

C
 
#2,612 ·
BoV 100% Atmo vs. Recirc Review (track tested)

Have run 3 different BoVs over the past 3400 miles on my STI. Stock, WorxTuning (Recirc), and Turbo XS RFL (100% atmospheric). 17 Track passes and 1379 miles Stock BoV. 13 Track passes and 971 miles on WorxTuning BoV. 15 Track Passes and 1044 miles on Turbo XS RFL BoV.

Fastest times on: (all 1/8th mile track with a 1.8x 60 ft)
Stock 8.519 @ 81mph (1.821 60 ft)
Worxtuning 8.484 @ 82mph (1.872 60 ft)
Turbo XS RFL 8.601 @ 80mph (1.869 60 ft)

Worxtuning was tested on completely stock car. 10 of 15 passes on Turbo XS were on stock car. Last 5 passes modification was HKS Carbon/TI catback exhaust (causesd overboost of 1.05 bar if gauge is accurate). Fastest Turbo XS time was after I installed the HKS Carbon TI Catback exhaust. Worxtuning is now installed again for track testing in 2 weeks (for aftermarket exhaust testing).

My review:

The Worxtuning BoV is only a little bit louder then the stock BoV, even at 100% atmospheric (design still vents air back to recirc even though set at 100% atmospheric). No idle problems. Drove 417 miles set at 50/50 and 554 at 100% atmospheric. Did not feel any different driving around town then with having the stock BoV installed.

The Turbo XS RFL is just that "Really F* Loud". Took 6 washers to have no idle problems. With stock STI exhaust it was alot of fun to scare folks and show off to the Honda that pulled up and revved at me (since the stock exhaust is quiet). Someone even questioned if I was spraying at the track. With the aftermarket exhaust it just sounds out of place. I also found myself getting worse gas mileage having to much fun with this BoV. But at the times I wanted to just be quiet and drive through town it still made noise around 3krpm (no hard excelleration). Shifting between gears felt like I was getting tossed forward in my seat. I got used to it over the miles but passengers not used to it will notice it.

After switching back to the Worxtuning tonight it is extremely noticable and a recirc BoV is a much more comfortable drive. I drive sporty and you can tell the difference between a recirc and a 100% atmospheric BoV after 1044 Miles.

For comparison the Turbo XS RFL track time of 8.601 (with HKS Carbon/TI catback exhaust, fastest time) was the same night my friend got a 8.37x @ 83mph (DCCD set to lock on this run) on a stock STI with no mods whatsoever (stock BoV). His previous best was 8.561 the night I ran the 8.484 on the Worxtuning BoV. Not the best comparison since its 2 different driving styles but it was 2 STIs running at the same track at different ambient temperatures on those nights..

Coop
 
#2,615 ·
HKS BOV adjusting question

hey i didnt know where to post this but i have an hks bov and found this quote on the internet "No matter how loose you adjust the bov, it will not leak. However, if you adjust it too loose, the parts inside will come apart and possibly jam the bov." i was adjusting it yesterday and for a second the bolt came off (no more then like 5 seconds it was off) i was wonder if this qoute would apply to me.
 
#2,616 ·
GFB Hybrid Blow Off Valve - 50/50 vs 100

Alright, some know, some don't... I have a GFB Hybrid BOV. So, if there was any doubt, this should clear that up!

So, I'm talking to RSMatt today, and I'm telling him I'm thinking about getting an RFL since the GFB just isn't doing it for me. Pretty loud first thing in the morning, but quites down after the engine completely warms up. Go figure! Anyway, he asks if I'm running it at 50/50 or 100. Well, the instructions I got were to run it at 50/50, and I couldn't find a thing on here about setting it to 100. I did look. Go, do a search! I couldn't find squat. Thought about asking, then I had decided not to since... Well... 50/50 is what the GFB Hybrid is best for! So, he says set it to 100 and it should get louder. I tell him I have no idea how, he explains it... A short while later I get off the computer and go to the car!

MINI PROJECT!

So, I get all that done... Start the car, rev the engine... Really nothing. To be expected anyway! I need to take it for a drive!

Just turning off my street I noticed it. Even low shifts you get sound! Full blasting sound at 5k!

Now, here's some stuff I noticed.

1.) The sound is no longer "Ptssshhhhhhhhh!" It now sounds more like some air powered laser gun? :confused1 Or should I say, "Ptzeeeer" I think the sound is shorter as well. Louder, YES! Not seems shorter and the tone is different.
Any one know if that's normal?

2.) Engine seems to run slightly deeper, and response a little more stiff... Or rather what I mean is at idle my ears pick up a slightly deeper sound than normal... Almost thought somebody changed my exhaust and stuffed it under the hood of my car? :confused1 When I say engine response seems more stiff, I mean when I go to leave from 1st gear, the car seems less hesitant. Like it's much more eager to go. Maybe I'm crazy?

3.) Here's where I know I'm loosing it. Maybe I just haven't paid enough attention to it, but the tone of the exhaust seemed a note deeper and a note louder. Now, I know that's really impossible... Then again, the RFL apparently can cause some rough idling on the WRX, or so it has been talked about. I don't know what the symptoms are, but perhaps these are similiar???

Anyway... Anyone else with a GFB running at 100 notice any of this? Or am I just losing my mind?
 
#2,617 ·
I noticed most of those things when i had my gfb set to 100%. I like it for like the first week, but then after that it drove me insane so i removed it. As far as the exhaust being deeper, that didn't happen with me.
 
#2,618 · (Edited)
OK, so I'm not really crazy about all that except the exhaust. Which I've come to the conclusion that... I just really have paid any attention to just how loud the car is stock anyway. More than likely since I compare my quiet car to the other WRX parked next to me... My father's with his TXS axleback muffler.
I know that sound all too well!
I can hear his car coming up the street, and seperate it from every other car.

As for how loud the BOV is now. Now going to matter too much. I always have the stereo up at like 7 or 8 (which is pretty loud to my ears), and never heard the BOV when I was driving. Maybe not at 100 I might notice it time to time. Which is what I'm hoping for... Not to mention terrorizing small animals and old ladies.
 
#2,619 ·
The HKS BOV holds boost by using pressure from whatever source you connected it to, (typically your manifold) to hold the valve closed while traditional valves use a spring on the other side to regulate when to blow off.

Think of it like a door, when its closed the pressure holds the door closed from the inside (not allowing it to leave the room) the more pressure (the harder your pushing on the wrong side of the door) for it to open so your closing the door more. Thats why the HKS doesnt leak.

Traditional bov's use a spring from outside the door (you pushing the door closed) so if the spring is set wrong (ie your not pushing on the door hard enough) the pressure can leak, like all the movies where the sailors cant close the door where the water is rushing through. Thats why if the spring is set wrong the bov can leak...

Hope I explained it well enough, sometimes my analogies dont help like I think they will :D
IMHO the HKS is a far superior bov to traditional bov's... but thats just my opinion.
 
#2,622 ·
Diy Bov???

My friend has a 92 Talon and he disconnected some hose or something and now his car makes a BOV sound...

I was wondering if it was possible to do on a WRX without boost leaks or whatever can happen. I found this tutorial on the net:

DIY BOV

Would this work for a WRX? If so can somoone explain in more detail how its done?

Thanks!
 
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