I am curious about the flow size restrictions on the different models of the venturi's. I measured my venturi's restriction to be 7/64" which would explain the severe drop in flow - ~1/2" tubing size restricted down to ~1/8". I'm guessing the larger models, such as the 584/684/etc have bigger restriction sizes which would have less impedence to the natural flow through the venturi. I queried Mazzei about this and they are unwilling to give the restriction sizes of their various models as it's proprietary (don't know why as a serious competitor could easily just buy them and measure). I know Iunknown has ordered 584 and 684 models - I'll ask him about the sizing of those models.

My assumption is, and maybe I am incorrect, is that if I find a venturi with the restriction closer to the tubing size, flow/performance will be much better. Flow will be better due to less resistance and performance should be better with much greater flow to shear the CO2 (assuming that the injected CO2 does not limit the flow significantly). Are these fair assumptions?