legacycentral bbs

So just as an experiment, I took my friends 05 STi BPV and put it on my 06/07 WRX TMIC. I didn't recirc it.

As expected, it runs horribly rich between shifts, but when I'm boosting and just take it out of gear quickly the idle drops very low (around 500RPM) then rockets up to around 1,300 RPM and then goes back to normal idle. Almost like it's 'searching' for idle.

Sometimes it will even drop so low that the ECU can't save it and the car just dies.

Obviously, this was just an experiment and I've already put my stock BPV back on so no flaming. But out of curiosity, why does it just die like that? Does it have to do with the spring rate or running super rich?

With an open BOV the car runs crazy because you just let air it metered out of "the system" which will cause poor AFRs.

You can run other BOVs/BPVs with good results if you recirculate the air they discharge - I'm using a Eclipse BOV on my SS & it works like stock.

Some folks have said the HKS SSBOV works well even if atmo-discharged, I can't say as I have not used one on a LSS.

I can personally attest that a stock BOV vented to atmosphere will kill your idle. I was tracking down a boost leak and had removed my IC and reverted back to stock, save re-circ'ing the BOV and I had a hell of a time keeping the car running at a stop sign.

Once I re-circ'ed the BOV, all was well.

And BXSS is right, it has to do with the metered air and fuel. The ECU just freaks out when O2 readings aren't right at idle and the IAC can't adjust and all just goes south .

Thats weird a could run my SS with out a BPV or BOV (idling)

I'm assuming though that you had the outlet plugged? If so then you weren't letting any metered air out of the system. Otherwise, I don't know, each car is a little different...

I think this should go to a vote...

I run my car with a Greddy BOV vented off my TMIC. I have a recirc. kit but I can't make it fit. Regardless, my car runs fine. It's been like this for a year, maybe my ECU learned?

Hmmm I don't know. I know how the whole BOV thing works and I know my car runs rich between shifts (wideband tells me so).

It's not like the car can't idle with it on, because it will. It's more like when I'm really getting on it (boost wise) and then take it out of gear so I can coast, the idle drops hideously low and either it dies or rockets up to 1,300 RPM and then does that 2 more times and then idles fine.

I'm wondering if it has something to do with the stock spring pressure of the STi BPV.

And I just want to make it clear, this isn't an aftermarket BOV for an STi. It's the STi's stock BPV, just not recirculated...

yeah, you're getting all those problems because the stock bpv's are open at idle and it basically creates a big vacuum leak when its not hooked back up to the intake tract. i figured that one out the hard way when i ran a stock bpv on my car not recircing and it ran so rich it fouled out the plugs.

Haha ah ok. That would make sense then!

I had the same issue. I felt like an idiot.