Just wondering if anyone here is using a two stage powervalve or has had experience with them, what is the purpose of having two opening points?

ttt

IIRC, they have a lower total flow than a single stage. From what I've read, they are for emmissions style carbs on heavy vehicles. Or any carb running lean jetting I guess. The first stage at 12" or so is for going up a small hill or accelleration from a stop. The engine needs more fuel than the lean jetting provides for this medium load.

The first stage must be a very small amount of opening given the size of the fuel transfer ports into the booster circuit. I have decided to try and get some better fuel mileage out of my full size 4X4 pickup and thought this might be the way to go if I can jet on the lean size and make up for it with the powervalve when I stick my foot in it. The two stage deal might make this easier but I've never used one. Maybe I'll order one up and do some testing with a vacume pump.