Quote Originally Posted by bigb996
dont take this the wrogn way but if your doing a turbo project im surprised your even asking this question. The bov only makes the hiss sound when the excess boost from the turbo comes through the piping that sound is that air being released. Do some research before you do the turbo so you know what you getting into. good luck.

actually you are wrong...the excess boost from the turbo is released by a wastegate. BOV's release the compressed air when the throttle is closed not allowing it to get to the turbo