Blow Off Valves

[A//// Guy]

So since no one will try an answer my previous question about how my stock BOV would blow air out at idle, I did some research. It seems as though I was right an a few of you were wrong.

At idle the BOV will spill air out of the BOV because there is positive pressure in the piping before the TB, and the vacuum in the intake manifold will slightly open the BOV.

I verified that with this page http://www.racetep.com/bypass.html

So in this case the Mazda was running like crap (rich not lean) because some air that was being metered was being released out of the BOV and therefore creating a rich idle.

A strong BOV like a tial shouldnt open at idle like a stock one does so if it does there is either really strong vacuum or the spring is faulty.