HI - I'm looking for some help. I'm trying to design a low flow single piston reciprocating compressor. Here is what I have: -Piston bore diameter- 1.50 in -stroke- 0.100" -should be able to go up to 30 psig average pressure will be 20psig -I am looking for the air flow to be 4.00 lpm at a back pressure of 20 psig -I believe the rpm of the motor should be about 2700 rpm How do I calculate what torque will be required at a back pressure of 20 psig and obtain a flow of about 4 LPM. I would really appreciate the help. Thanks!