How dose a By-pass valve know when to open?
 

I just ordered a by-pass valve for my powerdyne. When I install it is there something that needs to be set? How will it know how much pressure to open up at?

It works by vacuum. It goes between your outlet tube which goes to your throttle body and your intake tube. When your engine has vacuum it sucks the by-pass valve open to let the boost go back into the superchager. The vacuum hose will go to the same vacuum source has your FMU unit. This will keep boost from being pushed against your throttle blade.

It can open two ways.... if the pressure is more than 125 or so psi or when you let off the throttle. I'm sure it will only happen when you let off the throttle though. ;) You will need to go down to your local auto store and buy a vacuum t-fitting and some new hose to hook up your by-pass valve. The valve is open with vacuum (at idle) or as you let off the throttle. You should be able to hear it as you let off the throttle. You can have it vent to atomosphere or re-route the air to your blower inlet tubing (recommended).

manifold vacuum