HVLP needle size question

[regg187]

Hello All,

have been a professional painter since 1995, mainly construction and airless sprayers but also HVLP turbines systems and hvlp conversion guns and old school bink's No7.
I have a question about needle size in an hvlp conver gun. I have an ASTRO Pnuematic fullsize grav feed gun. the original they sold before the QUANTUM. I have a 1.5 and a 1.9 needle and caps. I would like to know if I need a 1.3 for spraying auto finish. Here is my Question If I have the 1.5 needle and it atomizes paint well , lets say for simplicity I spray the same paint( viscosity) with the 1.9, now I know more material will come out and it won't atomizes as well, but if I were to set the material feed setting to where the needle couldn't move back as far so the same amount came out as with the 1.5 , shouldn't I have the same atomization as I did with the 1.5? If I am wrong can some one explain this to me? So If I restricted the 1.5 a little shouldn't It work the same as a 1.3 given the same paint viscosity?

this has bugged me for a little while. I know the need for a bigger needle to use with heavier bodied material , but auto paint viscosity seems generally similar within product types. AE's, Urethanes, etc. thank you in advance for your answer's Regg