Automotive Air Conditioning Information Forum

Hey guys, I've been reading and leading a lot from this site. I've been searching to see if there have been any previous answers about my specific situation, but I've been unable to find anything.

I have a 1990 Isuzu Trooper that originally came with a TXV system. I am wrapping up an engine swap with a supercharged Buick 3800 (L67). For better fitment I have the F body Camaro (L36) AC compressor and brackets. The 3800s use a V5 variable displacement compressor and from everything I've read it seems like the two systems are not going to like to be mixed.

My questions right now are what would be the better system? Use the V5 and convert over to a orifice tube or retain the expansion valve and look for a 10S17F or something comparable.

I'm in southern Arizona, so a better performing system would be more appreciated over higher efficiency.

Thanks!

GMs midsize FWD cars like the Achieva, Skylark, Lumina, GrandAm and the like in the mid 90s used an externally equalized expansion valve with the V5 just like your Trooper. I rebuilt the system on my grandmothers 1995 Achieva 3.1L V6 around 2005 and that system would freeze you out in Texas heat. I have also used the V7 LS1 F-car compressor with a couple Old Air and Vintage Air AC systems. They worked fantastic. Worst case you will need to swap the compressor control valve. I typically start with a Green 38 psi valve in retrofits running R134a and go from there. Truth be known most have a 40/42 psi valve and while GM went conservative for the OE setups most systems will deliver cooler vent temps without freezing up with the lowest pressure rated control valve.

Thank you! That is exactly what I was hoping to hear. I'll probably swap the control valve first and go from there. I didn't want to make all new hoses just to find out that I will need to switch to an accumulator system.

I do not know where the myth came from but it certainly is complete and total mis-information that a variable displacement compressor will not work with a TXV. My guess is that some of the aftermarket air conditioning companies claim it will not work to sell more compressors and mounting brackets. In the older days of vehicle ac systems the compressors did not even have ac clutches on them. Later, GM came up with the suction throttle valve which regulated the evaporator pressure much like a variable displacement compressor does.

I think that's the biggest thing I've seen. Most people say that you need a fixed displacement compressor on systems like vintage air, but no concrete evidence as why.

From what I could find GM used the V5 with multiple TXVs, even more modern block style ones like on the Cadillac Catera. The series III 3800s used a mechanical cvc and maintained the expansion valve as well.