Originally Posted by willwren
The VE of an Eaton M90 is rumored to be 95%. Doesn't leave much room for improvement.
Correct, and to elaborate a little on that remember that the roots style supercharger is a positive displacement pump. Every rotation of the M90 moves ~90ci of air. I used the ~ because this number is effected by Volumetric Effeciency. This is simply its theoretical output vs its actual output. Such as if you had an M100 (100ci capacity) and only 90ci of air came out each revolution it would have a 90% VE. Some of the air slips between the rotors, which is why you '94+ guys have teflon coating on your rotors.
Anyway, no matter what you do each rotation will only ever pull ~90ci of air, expose the rotors, port the heck out of it, do whatever you want; the space between the lobes will only allow that fixed amount. Below is a chart outlining the volumetric effeciency of the M90
This is by the people over at zzperformance. This doesn't leave a lot to play with. Especially since its impossible to get to 100%. Surely not so much of an improvement to take it up to 19+psi. Also, roots style superchargers are NOT high pressure superchargers. They are not designed, nor do they do well, at that high of boost. You may see some of the larger displacement pumps pushing those numbers, but thats the cap on most of those also. My guess is somewhere in the fine print they spin the heck out of this thing.