what determines the loudness of the bov, is it the amount of boost the turbo is pushing or what?

 

That and how much pressure is in the piping. Also what kind of blow-off valve you have. Some have different size holes for bleeding.
Also it depends on what kind of wastegate you have i think....not sure about that though.

 

well i am going to be buying a kit from tmaturbo and they have to different kinds

 

some bov are designed to make the loudest sound possible.....but i dont know enough about them to tell teh difference between it and a standard

 

boost psi & size/shape of the vents play a role in it.
The longer/larger vents make more of a low pitch sound, the shorter/smaller vents make a more high pitch noise.


= loud, high pitch


=little quieter, lower pitch