BPV confusion

[James614]

Okay, so in the process of investigating my boost leak, I naturally turned to my BPV. After searching on here, I've noticed Josh says you shouldn't be able to blow through the BPV. Well, the one on my car you could blow through with no resistance, but it the air comes out the vacuum nipple and not the far side of the valve. Blowing or sucking on that nipple doesn't do anything but move air.

So, I replaced it with another one I have. This one you couldn't blow through at all. And if you suck or blow into the vacuum port, no air escapes and you can discern something moving inside.

Sounds good to me, except with the 'good' BPV on there the car runs like shit. I get reduced BPV noise on lift off, the engine acts like it wants to stall between shifts, and getting on the throttle again is sometimes met with hesitating. Builds boost the same as far as I can tell though. There's no cracks on it that I can find.

Put the old one back on, and the car is happy again and I have a normal BPV sound again. Wtf? For now I'm sticking wth the one that runs better, but I feel like I must not know anything about how these guys are supposed to operate. And the info about them is usually "I vent mine to atmosphere and its fine" > "that's a terrible idea" > "my stock one is fine to eleventy billion psi" > "just buy a mk3 Supra/Forge BPV"..

I actually like the idea of getting the Forge, but an OEM one would be a little less than half the price new. And I d;not wanna wait for international shipping...

[cj91legss]

Here's a thought, disconnect the vacuum hose to the BPV and just plug it. Drive the car and see how it does. Yes there's going to be a bit of compressor surge because the boost has nowhere to bleed off, but it'll rule out if you have 2 bad BPVs or you still have a different problem.

[James614]

Wait, I dont get what thats supposed to accomplish. How can capping that line off tell me if the bpv is bad?

[cj91legss]

Assuming the diaphram is not working inside the bpv and it is stuck open.

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[James614]

I dont think the diaphram is stuck open. I think on the one thats working fine for me, the seal between the diaphram and the upper nipple is gone. On the other that make the car run shitty, I suspect it may be stuck closed. In both cases I can build boost close to the same.

Im gonna wait until I build my boost leak tester before I worry about these guys any more.

[kimokalihi]

Did you hook the good one up the right direction of flow? My suggestion would be to get the ebay bpv. You'll need larger hoses since its got larger pipes on it but it works fantastic and I absolutely love it. Its inexpensive and good quality. I had compressor surge pretty bad when I shifted but when I replaced mine with the ebay one it was gone instantly and now its just got a quick pshhhh sound. I should also note that I upgraded all the hoses and the bpv pipe off the intercooler to match the ebay bpv size and I also relocated the bpv pipe from the stock location after the intercooler on the 06 wrx tmic to just before the intercooler.

[cj91legss]

I use a turboxs type h bpv. Kinda spendy if you're on a budget but I Like it.

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[James614]

The location of the bpv on the early WRX/Legacy EJ20G makes it really hard to plumb in something with a larger diameter, or that doesnt have the straight through shape (I was looking at the SiliconIntakes.com Type 44, but I dont see how I could make it fit). And ive got silicon hoses for it all, so I cant really do much in the way of getting rid of that choke point on the stock connections.

And yeah, I installed it the right way. That was the first thing I checked when the one I thought was good made the car fall flat on its face between shifts.

[Legacy777]

Do you have a hand held vacuum pump? If not, get one.....or while the one that makes the engine run "fine" is hooked up, take and hook an engine vacuum source up to the other valve's vacuum port, run the engine and see if the valve opens. The BPV should open when vacuum is applied.

The valve that makes the engine run "fine" is bad. The diaphragm is toast. If you verify the correct operation of the other BPV or get a new one and the engine still runs poor then you have some other issue.

[James614]

I actually do have a vacuum pump. I'll check the other one today to see if its stuck closed or not. If it is working okay, then I have some serious head scratching in store... but I'll tackle that when I actually know what its doing.

[James614]

Okay, so my good BPV is actually bad and my bad BPV is actually good, apparently. With 5mm/Hg applied to the nipple, you can hear the bpv open and you can blow through it. Release vacuum and it closes, you cant blow through it anymore. The one im running with definitely never opens.

So, ive been surging my compressor for probably the past year or so. Or possibly more. Great.

The only thing I can see causing my stalling issues with the good BPV is the recirculated air somehow escaping. But the good BPV doesnt leak at all. Does the turbo inlet get pressurized enough on recirc to potentially cause a leak that doesnt present under vacuum?

[James614]

Well, got the working BPV on, and checked thoroughly for any possible preturbo leaks. Couldnt find any. So I reset th ECU, and now it runs better than it did the last time I had this BPV on there, though it still hesitates on upshifts and tries to stall on clutch-in coast-down once in a while. Ill give the ecu more time to learn and see if it improves.

There really isnt enough distinction between compressor surge and bypass whoosh on these cars IMO. I feel like I may not notice if the sound changes over time again in the future.

[Legacy777]

Keep us posted on whether things improve or not.