I just went and revised the dimension check on the 2 units (attached)

something to consider given the last 2 posts.
The breadth of the units is similarso one could assume the rotors to be similar diameters and dare I say - shape. I'd figure from a manufacturing standpoint they are probably cast the same and the 1.6L unit is simply cut off shorter.
Looking at my guesometric diemnsions of the 2.3L body when scaled from the actual dimensions of the 1.6L on my vehicle, the rotor case is 278mm long against 220mm = 26% longer
1.26 x 1.6L = 2.02L - so you'd need an additional 14% speed to get to the 2.3L.

That's assuming of course the 1.6L and 2.3L is confirmed - I havent been able to do that as yet.
IHI isentropic charts for the "2.3L" are nigh impossible to find. The assumption everywhere is to just use the Lysholm charts.

Assuming similar casting/balance/manufacturing processes - if we can check out the bearings for the 2.3L which are obviously good for 23,000rpm on the 3 lober, I would be suprised ours is very different - but we only run our 3 lobe shaft at 15,000rpm.....hmmmmm....interesting.

L8tr....The internal gearing on the 2.3L seems a bit unnecessary really - maybe for the purposes of what I am looking at here - the front gearing arrangement of the 1.6L could be fitted to the 2.3L lobes and simply spun with a 62mm pulley. Same end game - but you dont have this longer snout - given we are pushed for room.
given upping the kWs transfered - slip may become more of an issue - but saves a whole 2nd belt and pulley complication.

Apologies for those who - have heard it all before.