Formula for equivalence calculations of pressure and flow

One day I'm going back to college to get my ME degree, if I don't die from old age first . Now..

I'm trying to fashion a Ranque-Hilsch tube to the exhaust of an internal combustion engine (ICE.) Most of the available information on these devices state a requirement of x psi (I've seen from 50 to 100,) but these are relatively small units with what appears to be 1/4" to 3/8" inlet ports. I'm looking at something more in the 1.25" to 1.5" range. So understanding PSI is a byproduct of flow, and that the larger inlet will "flow" much more air, how can I calculate orifice sizes to be proportionate.

It is a little difficult to describe if you are not familiar with the function of these tubes, but the fundamental operation best I can gather is rapidly spinning vortices, being forced to coexist, one within the other, in a confined space. So if the desired effect is accomplished at 100 psi air inlet pressure, fed by a 1/4" tube, culminating in a 1" cavity.... then using a .5 liter piston ICE, I'd need a ???" tube feeding at ??? psi, culminating in a ???" cavity. I know there must be some math that can give me proportional equivalents.

TIA for your help.