I know it doesn't blow out into the atmosphere so I would guess it doesn't make the sound. But the reason why I'm asking is because my friend has a 1.8t GTI with a bypass valve that came stock on it. When he put a CAI on it it sounds like he has a blowoff valve. Everytime he hits the gas and lets off of it you hear a wooosh. Then he put a diverter on it (not sure what that is, if somebody can explain that to me I would appreciate it) and the sound was even louder. I am thinking about going with the JWT when it comes out and that's why I'm asking about the bypass valves and if it will make noise since JWT's kit will supposedly have 2 bypass valves. Can somebody let me know? Thanks for your help. I find this board the most knowledgeable. Too bad the site is down most of the time.

 

Technically speaking, they are the same thing. I ran a HKS Racing Bypass Valve on my single turbo RX7 and just vented it to the atmosphere. Most factory blow-off valves are actually bypass valves, so you can just vent it to the atmosphere and it will make a louder sound if that is what you want. I would check the Audi forums however to confirm that it is safe to just vent the bypass valve to atmosphere, cause it can cause some cars to stumble or stall (my friends VR4 did).