Originally Posted by REVIT93RX7
Hey Woody, I applaud your efforts in providing the information about the SC. I tend to believe in real data. If power is applied to the SC clutch then the clutch is engaged period. Now if there is some other mechanism bleeding off the excess pressure then I can understand the boost/lack of boost issue. Maybe we are missing something? I know from running turbo cars for many years that you must bleed off execess boost when the throttle is closing. Otherwise boost spikes etc. and that is never good.
The problem with turbos' and the boost spike is that the boost is seen before the throttle body plate. If you let off of the throttle the boost will continue to push forward and can cause damage to the throttle plate. To relieve the boost spike a blow off valve (BOV) is used. The BOV senses the boost spike and releases it rather than letting it "slam" into the throttle plate or blow off your intake hoses.
My 8/71 super charger does have a BOV located after the output of the blower. It's not there to relieve pressure from boost, it's there in case you get backfire from the engine (granted if you produced enough boost it would override the BOV spring pressure). When I let off the throttle air simply stops flowing and thus the boost stops.
And yes the blower could be turning 6000 rpm and still show a vacuum condition if the load is not high enough. Example, accelerate at a medium pace say to 55 mph and observe your vacuum gauge. While the actual acceleration is occurring you will see boost, once 55 mph is reached and you are cruising you will see that your boost gauge is now showing vacuum. And yes, your supercharger is still engaged.
Make sense?