OK, I prommissed not to mess up the daily driver, but I'm going to anyway, I've found an easy 5th injector set-up to add fuel under boost (check link) and I can aquire a fairly new Eatom M45 (from a New Mini, which was given an M62 upgrade).
Aiming at about 0.5 bar boost (7 psi), what rpm ratio should I have between engine and supercharger? If I understood the Eaton flow diagram correct, the M45 displaces about 0.022 cft of air per revolution, which I believe is 622.6 cc. I need 900 cc per engine revolution to fill the cylinders 100%. To fill to 0.5 bar, I think I would need 1.5 x 900 cc per revolution, ergo 1350 cc, ergo have the supercharger spin at 1350 / 622.6 = 2.2 times engine RPM.
Does the above make sense? Or am I off-track completely?
Please advise,
Best regards,

Hugo