"In the United States, FAA specifications state that engines up to 1,000 cu in displacement require an 0.040" orifice diameter, 0.250" long, 60-degree approach angle. The input pressure is set for 80 psi, and 60 psi minimum cylinder pressure is the accepted standard."

A lot of automotive testers use 100 psi so the psi numbers represent the percentage...no math required.