so... cold co2 gas in the car not a big concern for asphyxiation? surely while driving down the road it's not a worry, but I'd think it could be dangerous at stoplights and parked...

The ICE A/C blew cold for about 2 hours of a 4 hour trip. Real cold. It was great until my BTUs ran out. But, being BRITISH THERMAL UNITS, I expected them to leak out.

I left in the evening so the sun went down about the time I lost cooling. Best trip I've had in that car in awhile. Eng temp never got above 90c with the condenser removed.

Joules are the SI equivalent, but only available where metric HVAC is sold. Tons (heat equivalent to melt a ton of ice) are a common HVAC consideration in the US and available everywhere.

while the btu figure should be the same, a ton of refrigeration/air conditioning, is the amount of heat removal needed to make a ton of ice... in one hour. the figure should be the same because all the heat needed for the phase change should be taken in by the phase change back to water.
it's the way I was taught refrigeration theory, so it may not be correct, I'll research it a tad...
actually, it's in a 24 hour period...
and it's the amount of cooling or HEAT absorbed by melting a ton of ice in a day... from the definition I've read so far. but like I said, the inverse is true, so it's the same amount of heat removal needed to turn a ton of water already at 32°F into a ton of ice...

Real cold . . . meaning . . .

Just curious, what would happen if you were to pump liquid nitrogen through the system?

Of course it would need to be sealed some how.

I was getting 70 degrees at the vent with ice.

A closed loop cooling system would probably last longer than the ice.

The only other system that I would consider is installing an old recip. air compressor to run a venturi gun (that painters use to attach to their painter suits) that drop the air temp to about 50 degree and run the cold air thru the evaporator.

May not produce the volume of cold air it would take to cool the cabin.

you could runn a small ac window unit off a nice inverter packed away in the trunk. then run high pressure ac lines to the evaporator in the cars dash and refil the unit with 134a. I want to install a more modern scroll compressor or something in place of my r4

Where is this "rear vent" that you speak of?

reach down behind the center armrest. It is the vent that provides cold or ambient air. It has a slide control just below the vent. Manual says close this in the winter b/c it would let in outside air. while running AC it blows cold air.

I just keep mine closed all the time as I get better air pressure from the front and there is rarely anyone in the backseat.

the coil would rather rapidly get covered in a thick layer of condensation ice, blocking all airflow through the coil.
of course, if you SEALED the liquid nitrogen it would assume vapor pressure, and no cooling would take place, it would then rupture the thin aluminum piping, and vent the nitrogen. only steel has the structural integrity to handle the 2000+psi vapor pressure of nitrogen...
and it would take THICK steel to handle it...

Sooooo, what you're saying is, thats a bad idea..................

that depends on your definition of what "is" is

Oh know, you're not one of those guys are you..

AND HE LOOKS LIKE SUCH A NICE BOY, TOO.

you who? and "those" guys? whatchutalkingaboutwillis?
:D