I took the back cover off hoping to increase the IP, but even after drilling out the staked dimple a little on the adjustment screw I was unable to turn it with reasonable force. I didn't want to break something and totally wreck this thing, so decided to open the first stage up from this end by removing the four screws.
62.reg dry.JPG
The first stage works came out in one assembly leaving this cavity and exposing the HP poppet, circled in red. Pressure relief valve seat is circled in purple. Poppet has an adjustable screw that if screwed in some may allow it to open more to allow increased air flow???
Trouble with that is, after loosening the jam nut it still didn't want to screw in any. The poppet material seems a little delicate to be forcing too much, so I think I'll leave that alone for now.
64.first st body.JPG
Turning attention now to the bellows assembly, which seems to do basically the same job that the spring and diaphragm does in diving regs. The threaded shaft in the red square operates an L-shaped lever that closes the downstream HP poppet with the end at arrow, so it seems like backing that shaft out a little might let the IP come up a little and/or let the poppet open a little further from the very small volcano orifice. I backed it out one turn, but didn't seem to make much if any difference on the bench. May try another turn later after I give this a dive.
63.first stage bellows.JPG
I have this thought that the bellows capsule may work counter to what is desirable for diving.
Still trying to wrap my mind around this, but as flying altitude increases the bellows expands at lower ambient pressure, allowing the poppet to open more to allow increased Oxygen volume in the breathing mix. When diving, the ambient pressure increases, collapsing the bellows more and more. That pushes the L-shaped lever into the poppet screw, decreasing the poppet opening the deeper you go!
I welcome any thoughts on this subject.