More capacity requires moving more refrigerant through a larger evaporator. This requires a larger condensor, too.....

Storing liquid freon in a second reciever/dryer will only help until it blows through -- the real limitation is the capacity of the compressor at idle -- it only moves what it is designed to do. Smaller pulley will help (it runs faster), but you risk overspeeding it on the highway.

The old York or Delco systems were better in this reguard -- they ate horsepower terribly, but since the were designed to have huge capacity and only operate intermitantly, they will keep you cool in hotter conditions. Hard on the cooling system though, and will blow the high pressure hose if the aux fan doesn't run (I know, I did).

Be carefull not to overcharge with 134a -- it requires lower pressure on the low side to cool properly, and make sure if you are using the temperature scale on the guage set that it is for 134a and not R12 -- temp and pressure are the same for R12 in the evaporator, and you never want to go below 32 psi with the expansion valve open (to prevent freezing). 134a need to be mroe like 28 psi. Note that when the expansion valve closes (if you have one), the pressure can drop to zero.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!