Charging 134a

My Dear experts :
There are some constant coefficients to define the refrigerant charge of typical R & AC
system which operates on R12 , R22 or similar .
but I seriously want to know a common rule of estimating mass charge of the other
refrigerants versus cycle , tonnage and inside volume of systems .
For Exp :
I have recently designed and installed a splite air conditioning system on typical passanger
car with followiong specification :
Compressor : 2pieces 4P15.2 (Bitzer)
Refrigerant :134a
Era.Temp : 45*F (Dx)
Cond.Temp : 65*F (Air cool)
Ambient Temp : 50*F
Total System Volume :120 lit
Reciever Volume : 10 lit
How weigh of R13 should I prepare as a charge ?
What is the physical property of result of oil (Ester BSE55) with air or moisture .

This sounds like a more detailed repeat of your previous post.
If you have an expansion valve, install a liquid line sight glass and charge just enough refrigerant to clear the sight glass of bubbles.

How can a system for a passenger car have a volume of 120 Liters?

If the ambient temperature is 50 F., why do you need A/C ?

Ester oil should not be exposed to moisture or air. If it has been, it should be changed.

Good luck!