BOV issues

[puppet]

They can take in quite a bit of air. I'm using an HKS by-pass type ... it allows for recirculation (if you want) to the turbo inlet hose. Mine recirculates. If I take the lower hose off with the engine running, it'll suck fingers in. Doesn't shut till it senses boost.

[mcglsr2]

Yeah, that's pretty much it. The little Mitsu turbo is the only one that creates boost at idle, but there is that instant when you open the throttle and the BOV isn't closed yet where there will be a small vacuum. Larger turbos won't boost at idle, so the BOV will suck air because it is the path of least resistance in the intake. This is even more true if the BOV is after the IC.

okay, that's what i thought. i spent some time making sure my thinking was correct before i installed the BOV and filter. glad to see i wasn't totally off base