SO.. if a BOV only opens when it senses a vacuum, when does it close?

At idle, my BOV sits wide open.. but if it's open then, does it mean that it's
open until the turbo pushes enough air through the BOV that all the air cannot
flow through the BOV, causing a pressure situation?

Wouldn't it be more efficient to blow-off only on a boost to vacuum transition?

I'm just wondering why my BOV sits wide open at vacuum, and when does
it close?

 

you got it backwards... a bov is closed... it gets rid of compressor surge by opening when you let off the throttle. if yours is always stuck open i dont see how your turbo system could be running anything over 2 psi. (just a random number i threw out there..)

 

damn, i don't even have a blow off valve yet.

 

A BOV is supposed to open when there's a sudden change from 0 or positive manifold pressure to vacuum. It's the change in pressure that opens it, not the pressure(or absence of pressure) itself. At idle, under vacuum, it should be closed, and when you rev the engine up to 0 manifold pressure it should stay closed, and when manifold pressure drops back down to the vacuum side, it should open, then shut and stay closed again.
does that make sense?

 

Makes total sense...

Only thing is that for some reason, at idle, my BOV is wide open (I can feel/hear
air sucked in.) I don't have any problems with boosting up to 7lbs..

I have the Vortech BOV that came with the Revhard kit (they started throwing
those in there instead of the Greddy Type S).