Topic: Turbo Blow Off Valve Noise

[Audi Quattro]

I don't want to sound like an idiot or anything, I have a 98.5 Audi A4 with garrett 2871R turbo, with forge bov, completly stock motor, running 25psi. I wont to know how some cars you can hear the blow off valve while reving your car.

[Hawk296]

Castle can do the noise for you. Just have him ride with you.

[jm]

I don't want to sound like an idiot or anything, I have a 98.5 Audi A4 with garrett 2871R turbo, with forge bov, completly stock motor, running 25psi. I wont to know how some cars you can hear the blow off valve while reving your car.

Its based on the type of valve.  Our cars came stock with a 'diverter' valve which re-routes extra air back into the intake system.
Blow-off-valves vent the extra air to the atmosphere -- making noise.

More here
http://en.wikipedia.org/wiki/Blow_off_valve

[Audi Quattro]

Yeah, mine was doing that and hard turbo surge. So I made it so it re-routed back into the intake. But I was ment to say if im stopped at a light, and I rev it up why dont I hear my blow off valve go off? Like on some cars ive heard it

[ken]

You only hear the noise when the boost is vented into the atmosphere.  The air is metered though, so when you do that the air fuel ratio gets messed up.

[jm]

So I made it so it re-routed back into the intake.

Because you've done this you won't ever hear it.


EDIT: this is a good post, actually about turbo surge, but which explains BOV/DV as well http://www.tremek.com/forum/technical-discussion/4407-what-turbo-surge.html#post22844