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

[FearTheWagon]

i recently bought and installed the GFB WRX Hybrid version 2 BOV and im being told now that the stock BPV is actually better for the car. what gives? can someone please enlighten me on this? thanks!

[cnk]

There are many threads on this if you search for BOV. Basically, the stock valve is a recirulating valve that vents air back in to the intake track. When you use an aftermarket BOV, it vents the air to atmosphere. The air has already been metered by the MAF sensor so what ends up happening with an atmospheric BOV is that you get a slight rich condition during shifting. It's not really a big deal. For most people, sticking with the stock valve is fine as it holds pressure pretty well. However, it has been known to leak so some choose to replace it with an aftermarket BOV or crush the top in to increase it's holding capacity.

Calvin

[FearTheWagon]

well my concern was a loss of performance using the aftermarket BOV since people have been saying rich conditions hinder spoolup that lean conditions cause a "flash" or mini explosion keeping the turbo spooled as one of my friends put it.

[BoostedBoxer]

Originally posted by FearTheWagon
well my concern was a loss of performance using the aftermarket BOV since people have been saying rich conditions hinder spoolup that lean conditions cause a "flash" or mini explosion keeping the turbo spooled as one of my friends put it.

Or "backfire" . As the "rich" exhaust from the aftermarket BOV not recirculating is sitting in the Downpipe, the hott exhaust coming out of the compressor housing hits it and causes it to ignite again causing flames or backfire.

[cnk]

That's afterfire, not backfire. Backfire is when combustion takes place in the intake track. . .not a good thing. Afterfire is when combustion takes place in the exhaust.

Calvin

[FearTheWagon]

actually he said the lean condition caused a sort of anti-lag like the system in wrc, i want to disagree but could you enlighten me on it?

[kpxplaya415]

Originally posted by FearTheWagon
actually he said the lean condition caused a sort of anti-lag like the system in wrc, i want to disagree but could you enlighten me on it?

I'm pretty sure that the anti-lag systems on WRC cars are indeed that. It's an addon system to your car and blah blah all this technical stuff but bottom line is you don't have it. Aftermarket BOV's cause the car to run RICH during shifts, not LEAN and your friend probably isn't the most knowledgeable about WRX's

And BoostedBoxer explained what the flames were a result of so there ya go.

[FearTheWagon]

thank you KP that answers part of my question but which is better for during shifts, rich or lean? lol and yea hes a hondaphile so i should have known better than to trust him on subies

[cnk]

You always would rather run rich then lean. Lean can cause too much heat to build up that can lead to detonation. Since the momentary rich condition is occurring between shifts, it really doesn't matter. I think you're focusing too much on this scenario. . it's a few milliseconds afterall.

Calvin

[FearTheWagon]

well that momentary rich conditon caused by the aftermarket BOV or the lean caused by the stock BPV could cause a difference in whether the turbo is spooled or not or how long it takes to spool which could make a difference of a few tenths of a second which could determine a 13.8sec run or a 14.1sec run...

[cnk]

If you're that concerned about 1/10's of a second, then just stick with the stock BPV. The stock BPV does not cause a lean condition so I don't know where you got that idea from. I think you need to stop talking with your Honda buddies and do some more research on the boards. If you're on the stock turbo, then stick with the stock valve unless you want the noise of a BOV. There's no reason to install a BOV unless your stock valve is leaking or you are pushing boost beyond what the stock valve can handle.

Calvin

[FearTheWagon]

ok finally thats what i was looking for lol sorry it took so long to get it. in terms of overall performance an aftermarket bov does nothing except for sound? and whats the max psi the stock bov can hold without getting compressor surge

[cnk]

You don't get compressor surge from a valve not holding pressure, you get boost leak. Compressor surge is when the BOV/BPV is not releasing pressure fast enough and causes air to back up and stall the compressor wheel on the turbo. Some people have their stock BPV's holding up to 20 psi without any problems. Some have issues with their valves leaking as low as 14 psi. Personally, I feel that my valve is leaking and I'm running about 17psi with a VF34 on a APS DR500 FMIC. The boost built up much faster with an HKS SSQV and Greddy Type-S BOV, but I was getting compressor surge. I just ordered a APS FMIC BOV, which is designed to work with the FMIC so hopefully that will resolve my issue.

Calvin

PS - like I stated above, it sounds like you've been getting a lot of bad information from your buddies. . .I would stop listening to them and start reading up and doing more research so that you don't mess up your car in the future. This board has a lot of useful information as long as you're willing to put in the time to search for it and read through the posts.

[FearTheWagon]

i appreciate the valuable input, i guess ill stick with my aftermarket bov then since im going to be going stage 3 in the near future..mind if i ask you some other questions? how do you like your VF34? i was considering that if my friend cannot pull through and get the VF36s he found for pretty cheap(500 each). hes the only knowledgeable subie owner thats local to me that i talk to regularly but hes got an 04 with a worx bov and i put in his EBC and his exhaust and he says its not leaking one bit and it feels better than with the stock BPV so ill take that for what its worth. the turbos i was considering are: VF34, VF36, VF39 and thats pretty much it, im not looking for lots of HP seeing as im on my stock clutch and stock tranny, just enough power to preferrably hit low 13s or high 12s which im estimating would be about 350 crank hp? can the stock transmission hold that? stock clutch if i take care of it?

[cnk]

I like the VF34 a lot. It provides me with the power that I want without too much lag over the stock turbo. There's a slight bit of lag, maybe 100-200rpm's, but it's not a big deal. You can get a VF34 for around $675 shipped now, which is a pretty good deal. I've never heard of a VF36. The VF39 is the turbo used on the USDM STi. Not many people have maps out for that turbo so I stuck with the VF34. Most people get around 275-285WHP with a VF30/34. With a FMIC, you can usually get another 10-15WHP. This roughly translates to around 350HP at the crank. The stock tranny seems to be fine at this limit, but I wouldn't go any higher. Keep in mind, it's not necessarily whether or not if the stock clutch/tranny can handle to power, a lot of it has to do with how you drive. There are guys that blow their tranny's with the stock turbo, yet there are also folks with PE1818/1820's that are fine and still running on the stock tranny/clutch.

Calvin