Blow off Valve makes strange hiss...

[pizza boy]

I have the stock BOV on my rev4 tubby venting to atmosphere but somethings different now.
If I put mid-load on the turbo in 2nd or 3rd gear I can actually hear a long drawn out hiss from the BOV at low rpm city driving(2-3k rpm) it will only occur at this low rpm range and dissapears after 3200rpm. After hearing the hissing if I put more load at low rpm it will also dissapear.
Is this normal?

[Driftlimits Performance]

sound normal. All dump valves sound different under a little load as opposed to full load.

[^Trickster^]

The stock BPV has a dual chamber which makes it faster response, much like the more expensive dual piston BOV you can buy.

I have mine vented to atmosphere and I get the same hissing sound, its because theres a slight difference in pressure on either side of the throttle plate, at low revs its more noticable because the turbo is pushing out a slight ammount of pressure and the throttle is almost closed, so you have a pressure difference which the valve operates on, its nothing to worry about.

Graeme

[pizza boy]

Interesting..I was just worried as I presumed BOVs should only vent air upon lifting off the throttle..not during application of throttle.

[Chris]

If your BOV is open at low throttle openings then surely it will allow unfiltered air to be sucked in by your engine? I'd put it back to re-circ...Just in case. Don't want crap in the engine.