Why not to run an atmospheric BOV on a Legacy

[Legacy777]

This is true for any MAF based engine. The air leaking out at idle or free revving is horrible.

http://www.youtube.com/watch?v=kzzUa82wRlE
http://www.youtube.com/watch?v=JKXpXa7PLts

[gijonas]

That thing is clearly not adjusted right.The BOV on my car doesnt just kind hang out open like that at idle,I think if he tightened that knob a little he might have better results .

That said i plan on converting to recirc. at some point for other reasons.

[Mattheww044]

what may these other reasons be if you don't mind me asking? I am running recirc and plan on doing so until I get a standalone which won't be for quite some time. If you have standalone you dont need recirc though do you? As long as its tuned to run atmosphere right?

[Florin1]

isnt that what all blow offs do? Supposed to relieve boost once throttle plate closes?

[SLODRIVE]

isnt that what all blow offs do? Supposed to relieve boost once throttle plate closes?

That's exactly what a properly adjusted BOV should do. An atmospheric BOV will cause a *momentary* rich spike when it releases, but that's all that should happen. There's tons of WRXs and STis around here running just fine with a MAF & an atmospheric BOV.

[Buffman]

And the way it was explained to me is that the "rich" condtion from the VTA BOV is not really that rich and does not last long.

[gijonas]

what may these other reasons be if you don't mind me asking?

The noise gets old

And the way it was explained to me is that the "rich" condtion from the VTA BOV is not really that rich and does not last long.

Exactly.I see it on my LC-1 and honestly i only see it if it takes me too long to shift,plus it helps in the rally noise department as it facilitates a nice little backfire

[Legacy777]

If you have standalone you dont need recirc though do you? As long as its tuned to run atmosphere right?

If your stand alone is setup for a speed density system or MAP based system, then you can run atmospheric.


There is still some benefit for running recirculated as it helps keep the turbo spooled.

[cj91legss]

what may these other reasons be if you don't mind me asking?

The noise gets old

And the way it was explained to me is that the "rich" condtion from the VTA BOV is not really that rich and does not last long.

Exactly.I see it on my LC-1 and honestly i only see it if it takes me too long to shift,plus it helps in the rally noise department as it facilitates a nice little backfire

It can make everyone think you have anti-lag

I've vented to atmosphere for as long as i can remember... without my emanage installed (yet) if i am like pulling up to a stop light, sometimes my car dies. and i f*cking hate that. and it's all because of my BOV.

I'm currently looking for a wrx bpv or a turbo xs recirc to solve my problem.

Seriously i recommend a recirc, even if you have a tune.

[kimokalihi]

I have a WRX bypass valve if you want it. $5 Only problem is, it's missing the elbow that comes off the side.

[vrg3]

Some of it depends on how you adjust the atmospheric valve's spring tension. My old car -- the one n2x4 has now -- has a stock WRX valve on it that I modified (smushed with calibrated hammer taps) to increase spring tension so it's closed at idle.

It works pretty well but there are some weird part-throttle situations in which it screws with the air metering because the pressure differential between the compressor outlet and the intake manifold isn't high enough to keep the valve shut. That also screws with the fuel trims, of course.

[Jester808]

Some of it depends on how you adjust the atmospheric valve's spring tension. My old car -- the one n2x4 has now -- has a stock WRX valve on it that I modified (smushed with calibrated hammer taps) to increase spring tension so it's closed at idle.

It works pretty well but there are some weird part-throttle situations in which it screws with the air metering because the pressure differential between the compressor outlet and the intake manifold isn't high enough to keep the valve shut. That also screws with the fuel trims, of course.

That's what I get after I adjusted it, the car runs like crap after installing the BOV, and it started to run rich at all times, even idle it was being a piggy :p. My stock BPV broke when I was fixing some cracks in the Turbo Inlet Hose and I had to put this APS unit on. I didn't bother messing with adjustment when I slapped it on there, lucky Legacy777 spotted it when we were installing and tuning the Manual Boost Controller this past weekend.

I don't think these are necessary at all on an all Stock motor like mine, it ran better with the BPV leaking. I can't wait to get a Stock unit from the Dealer in a couple of weeks. Legacy777 went over the entire car with the Select Monitor back when I first got it and there has been a significant downfall in performance and reliability since I started having problems and putting this stuff on there. I need all new everything right now for it to run properly.

It's kinda funny though how the BOV smiles at you as it's just leaking air out . I adjusted it to the point where it won't stay open like that, but now it's too stiff and the car gets bonkers and stumbles when I let off the gas. It still blows air off though, I just hate the attention .

[HappyFrog]

The forge vta I had on my impreza worked fine, only problem was if you let go of the throttle just as it reached boost it would pop loudly. Otherwise there was no difference between running with stock vs vta.
I got a 01 wrx recirc on the legacy and had planned for a more subtle vta this time. After I had it tuned I decided not to though, the 01 bov sounds awesome with open filter and fmic, it opens and closes a bunch of times and it makes me smile every time. My wife was like "wtf just happened" the first time I floored it and the bov laughed at her

The forge was a bit too much for me though, it screamed loudly every single time you would shift no matter how little boost it saw.

[Legacy777]

Alex, I would probably back off the BOV, it sounds like you're getting compresser surge, which is going to be worse than running rich.

[Jester808]

Got it, I already did. I'll just have to live with it smiling and mocking me until I get my Recirc in.

BOV's are ghey on Automatics .

[91legacyawdturbo]

I never had any idle issues while running my hks ssqv. always ran good of course it ran rich for a moment but it closed quickly maybe it depends on the valve it self?

[brweber352]

I ran a HKS VTA, and it was fine at idle. It did run rich whenever it opened, just becasue it acts like a metered air leak. At low speeds and low rpm if I let off the gas quickly it was rich enough to cause it to stall, this got old real fast! If I was going fast enough it never stalled, but I freaquent the University campus and speed limits are slow. If someone pulled out in front of me or ran out in the road, I'd have to let off suddenly and it would stall. Stalling enough times in front of mobs of HOT coeds, and having to restart the engine is kinda embarasing enough to make you go back to a recirculating BOV. BTW I have an Automatic, if it helps any.

Now I just run a black Bosch style that can be found on many VW's, works fine and holds at least 18psi, and are very abundant at the JY.

Brian

[Jester808]

I never had any idle issues while running my hks ssqv. always ran good of course it ran rich for a moment but it closed quickly maybe it depends on the valve it self?

This is what I've been thinking too, while waiting for my Recirc I put on an HKS SSQV II because I wanted to see if a Pull-Type would have the same negative effect as the Push-Type, and it didn't. I did however use the FMIC setup as opposed to the TMIC with the bracket that bolts onto the TMIC, from what I've seen, alot of those TMIC setups are leaky.