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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





 
#2,478 ·
UPDATE:

So last week I was able to borrow a friends stock bov (thanks killaho) to do some testing. With the borrowed stock bov, I was able to build up boost slightly quicker, and was also able to hear the audible woosh of pressure released back into the intake circuit, via my velocity stack coming out of my stock air intake box.

I did come to the conclusion that MY stock bov has a lazy spring now (I probably wore out the spring with too much boost), and leaks air into the intake tract under pressure. Also, after shifting, my stock bov doesn't even give any sound out of the intake tract.

So I looked around, and purchased the Forge recirculating BOV. I was in a hurried state of confusion, and ordered it without doing any research on it, which is really not like me. I assumed it was a 50/50 bov, but it turns out it is a 100% recirculating bov. Yes I know, it is the same configuration as the stock bov, but my opinions are down at the bottom of the page to explain my choice, which I am pretty happy with. I installed it yesterday, and I have a few opinions on it.

The Forge recirculating BOV holds pressure a lot better than either stock bov I have tried. From idle to WOT, the car doesn't bog at all like it seemed to before. It also seems as though the motor is much more responsive at different rpm's. For example, I tried going WOT from idle, 2000rpms, 3500rpms, etc, and there was little or no hesitation. And this bov also gives a little more of a woosh out of the intake tract, which is kinda nice. But I have to turn off the radio to hear it. I like hearing the release of the air when I want to hear it, not when it is overbearing and annoyingly out there after every shift. And it also gives a little bling to my Hyperflow TMIC as well.

Thanks guys for your input on this topic. I really appreciate your posts and comments.
 
#2,481 ·
APS TMIC Blow Off Valve

I'm curious about this BOV and have a couple questions..

On APS's site it says..

"The large primary vent is designed to plumb back to the standard entry point which ensures the best driveability during cruise conditions and cures the problems seen with after market external single venting blow off valves."

I know BOV's that recirculate cause little to no problems with Sti's, but you dont get that great sound :cool: . Is that all APS is saying here? It recircs therefore negates a lot of the problems BOV's the vent the the atmosphere cause?

If anyone has this BOV please chime in!

Thanks!
 
#2,483 ·
Removed BOV today

After about 1200 miles, I removed my Blitz DD BOV today to see if it had any effect (good or bad) on performance. The idle quality and driveability is much better with the factory BOV reinstalled. I won't be putting the Blitz back on. It anyone is interested in giving it a new home, make an offer. I will ship it.
 
#2,485 ·
Im using the APS BOV too, absolutly no problems, the only difference in driving is the sound, and yes, it still is plenty loud, I acctually wouldnt want it any louder, they seem a bit pricey though, guess I was lucky, got it off Ebay for $100 as soon as the guy posted it;)
 
#2,488 ·
Graham Goode BOV install/vacuum hose loca.?

Installing the BOV but don't know where to connect the 3ft vacuum hose to. It goes on the BOV but won't fit over the T connector. There were no instructions and I can't see trimming the excess 2 ft of hose off. Is this where it goes? Back on the T splitter, or somewhere else? Anybody have an idea?
 
#2,490 ·
Same with my RFL. I do need a new BOV though, one that works. The stock one is on again but it is not performing up to par. The FMIC stopped the boost creep but the stock BOV is surging the turbo, Not smooth any more when you get off throttle and back on again.
 
#2,492 ·
UR2 SLO said:
Same with my RFL. I do need a new BOV though, one that works. The stock one is on again but it is not performing up to par. The FMIC stopped the boost creep but the stock BOV is surging the turbo, Not smooth any more when you get off throttle and back on again.
Id go with the aps bov, made to work like the factory one just more efficently.
 
#2,493 ·
Blitz Bov wont open

hello everybody,
I have Blitz Bov and it seems like the valve wont open. Eveytime I go into boost or let go of the gas it makes a weird sound compared to other blitz bov. Its seems to becoming from the intake. I have tried adjusting but it still dosent open.
Any help?

Thanks,
Silva
 
#2,494 ·
Did my BOV hit the hood when I let off?

I went from a light, no launch against a buddy's SHO V8 taurus thing, just messin around, bogged @ 1k, he got a car on me, I screamed by before the end of first and I pushed the clutch in @ 7k, when I did I hear a LOUD *POP* from the front, sounded like a boulder struck the hood or windshield!

So I pulled over to take a closer look, car not running in any sort of ill manor, I have the BOV cocked a little towards the driver's side fender (middle of horn faces about 1 o'clock) and it looks like the TurboXS RFL I have is pretty big, did the engine spring up from the driver's side when I let off and bang into the hood?
 
#2,495 ·
I have never had a Blitz BOV, but I know that all BOV's have a piston running down the middle of them. This piston goes up and down inside the main body of the BOV. The piston is lubricated with silicone grease from the factory. After the BOV has been on the car for a while, the grease gets used up, blown out of the horn, and dust/dirt gets onto the grease forming grit. The problem your experiencing is probably because the piston doesn't have enough lubrication to do its job, so it cant travel up and down properly.

Take the BOV off the car, and take it apart. Do a search for GFB BOV that I wrote A LONG TIME AGO. I put full detailed pictures of a GFB BOV. Fully clean all of the inner parts of the BOV with Isopropyl Alcohol to get all of the grease and grime out. Then put a nice thin layer of silicone grease on the entire outer piston area, as well as all of the parts you cleaned out with alcohol. Put it back together and try it again. It should help.

Good luck.
 
#2,497 ·
Are you getting a fluttering sound dude? Does it make the pssssh at higher RPMs or does it not make a sound at all?

You might wanna try loosening the spring as well...you just take a size 10 socket to loosen the nut on the top, then use an allen wrench to loosen the spring.

If you want, gimme a ride in your car so I can see, 'cause I have a Blitz BOV too ;)
 
#2,500 ·
Lilfoofighter said:
^^^ your avatar owns 10x more then before :p
LOL thanks :D
 
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