It's not just with r22 condensing ethylene - although larger compression ratio of a higher discharge pressure at the same suction pressure will increase motor power making it worse. Discharge temperature is from the gas behaviour, ethylene is just a hot discharge gas.

What Clemmaster is saying is that by reducing the capillary restriction (-length or +diameter) and also increasing the ethylene charge you can reduce the superheat on ST2 suction, which will lower the discharge temperature proportionately to the reduction in suction temperature of ST2 in theory.

The problem is that with such a large motor it might be a loosing battle, rotaries for A/C just aren't meant to run like this.

But they work great for a few hours at a time, making ideal benchmark cascades

Tom