It plays a little role but the main depending cause is, as Tom said, the superheat on ST2 succion and the ethylen quantity (that's why by using long captube with ethylene involve a very high discharge temperature as the quantity must be higher, and it involve a high static pressure too). That's also the problem you get when using ethylen on both 2nd and 3rd stage, you have to shorten the captube on third stage as the condensing pressure on 3rd is very low (>5bar), but if you put the most powerfull compressor on this stage the 2nd and 1st stages won't work the best.