Joe ....So if I am under boost like 2 or 3 psi like the OP described ... it is still OK to hear it leaking? I thought from reading your write up that you would only hear this when transitioning from vac to boost ? but not when under boost even at low psi?
If it is leaking when under very low boost wouldn't this mean I am loosing boost ?
Sorry I have ask you this before ...I must be a little Tarded
That is the way Polaris setup the stock BOV and a lot of the aftermarket. It is open at idle / part throttle and requires positive manifold pressure to close
Like this picture I stole off the web:
This is done to prevent compressor surge at the detriment of throttle response. If the system is designed and tuned correctly it is not necessary to bleed off boost at idle / part throttle.
I will try to explain better with boost / vacuum numbers.
Given that at idle the XPT makes ~13.5Ēhg or -6.6psi of vacuum you need at least ~8psi spring pressure to keep the valve closed at idle. At this point the vacuum is working against the spring thus subtracting from it's rating.
As the throttle opens the vacuum decreases with rpm to eventually zero. At this point there is zero differential across the piston and the spring is at it's given rating.
As the rpms build further and the same positive manifold pressure is applied to each side of the valve (intake port of the BOV & vacuum reference) do the differential across the valve remains zero. This spring still maintains it's rating and keeps the valve closed.
When the throttle is closed vacuum is created post TB. Via vacuum reference this value is applied to the top of the valve (piston) and it subtracts from the spring pressure. The intake side (bottom of the piston) still sees positive manifold pressure. So now you have a differential across the valve greater than the spring pressure and the valve opens and dissipates the manifold pressure until the differential pressure is less than the spring pressure at which time the valve closed again.
Example with general numers: You're on the throttle and making 15psi boost. 15psi is seen at the bottom and top of the piston so the spring pressure remains ~8psi keeping the valve closed. Then you let off the throttle, ~7psi of vacuum develops post TB, this is applied to the top of the piston while the bottom still has 15psi. So the vacuum of 7psi is subtracted from the spring rate of 8psi making it 1psi. Now a there's a differential of 14psi across the piston. The force on the bottom of the piston (15psi) oversomes the spring rate (8-7=1psi) and the valve open until the differential equalizes.
Sorry I got carried away with a long explanation.