Dave, yes I think that's what I have for metric gear formulas. Red are input values on my spreadsheet, black are calculated. I calculate V on the imperial side & convert to ml on metric side, so equation units should match. The screen grab is my approximation to your Porsche pump example using close-ish metric gears. Maybe that's not the right approach but having difficulty seeing why not. V (volume per revolution) is a function of W,D,L (only).

Part of confusion may be the same spreadsheet populated with Mikes engine pump guestimate. But I originally guessed his gear width (W) at 10mm just eyeballing his picture at the time. Your gear is only 2.29mm (0.090"). V is directly proportional to W.