so i was wondering when the blow off valve sould blow. Mine will blow even when its in vacuum. N ot alot of vacuum, but probably anythign less than 5 in hg and it will blow. It seems wierd to me that it would blow under vacuum so yea lemme know.

 

The stock BOV is open until the car is about to transition into boost. It then closes to allow boost to build and then opens again when the throttle plates close.

 

I think I understand what your sayinng so I am going to give this a shot.

Just because your boost gauge is under "0" boost doesnt mean that your tubros aren't spinning and building up pressure. It is not enough to go into "boost" per say, but that is why your car is not sucking as much air (i.e. it is still being forced in, but not a lot). The vehicle still has to let off that little bit of pressure to get back to it's needed vacuum level.

I think this is what you are talking about, but if it is not, I am not sure.

-josh

 

that sounds about right. its a blitz bov and i see what you mean by it still building pressure even if not at boost. Thus it would still need to release some.