Same CBVs I was talking about. A simple Bosch CBV. Watch out though, they do vary according to part number.

 

JUNKCLTR,
I bought and installed the 710n.
Do you know how muhc vacuum it needs to open?
it seems as if it's not opening, becasue i'm still real rich at idle..
also...do you have a pic of the direvtion of flow for this valve? maybe i have it backwards/

 

The link I posted in this thread on June 20 of this year shows the amount of opening per vacuum. It also shows the direction of air flow.

Right before you go into boost you will hear a lot of air being returned to the air cleaner. That would tell you if it is connected properly also. When in boost it quiets down and the turbos start to make noise. I did not measure the opening vs. vacuum.

 

the main difference between a blown car and a turbo car when it comes to bypass, is that the blower is ALWAYS making boost.......so its hugely beneficial to the system to have an open bypass for part throttle driving and no load conditions.

depending on how big the blower is, there can be a truly massive amount of air moving through the system at WOT/redline under load.......if you snap the throttle shut without a bypass and the tubing holds together you can blow gaskets, or worst case scenario even bend the throttle blades.

adding the bypass was one of the most important driveability developments with centrifugals. And as far as the entire "who lifts to shift anyways?" argument......everyone does.....if you powershift your car driving to the store you have mental problems

 

PS......there are alot of guys running F series prochargers that are using 2 of the huge atmospheric bypasses now......even with my f1R the pressure inside the hat with the bypass open and the car in neutral hits 15psi above the throttle plates