LS swap - poor A/C performance

[foamypirate]

I just completed my A/C system on my LS swapped 88' Crewcab, and I have to admit, I'm not entirely happy with its performance. The system is all new except for the evaporator, which was flushed. It has an ACDelco parallel flow condenser in it. Compressor is a Denso 10S17F. I used a Ford blue orifice tube, 8 oz of PAG46, and the shop that charged it said they only had to put 32 oz of R134a in the system. I vacuumed the system immediately after buttoning everything up, and the accumulator was the last thing installed. The A/C shop also vacuumed before they charged, per standard procedure. The accumulator and outlet fitting are sweating, and the suction line fitting at the compressor is cold/cool as well. Compressor discharge is hot, condenser outlet is warm. The evaporator inlet, at least where I can feel before I run out of visible tube, is cold. At idle, pressures were about 45-50 low side, 350 high side. I am running 2 LT1 Camaro e-fans with proper fan shroud, and they come on with A/C pressure as they should (controlled by the PCM). Spraying water on the condenser dropped it to ~300-315, which is somewhat expected? At 1500+ RPM, the pressure would quickly rise enough to cut off the compressor via my HPCO (~455 psi, according to the spec). The cooling is OK, but seems like it should be better with a parallel flow and modern compressor. Once the sun went down, I took it for an extended highway drive, and the lowest temp I saw while moving was 51-52*. It actually got slightly cooler at idle - 49* or so. Temps were still in the 90F range.

Another drive during 98F heat resulted in a low temp of 60F after over an hour of driving.

I've tried tweaking the charge a few ounces in either direction without much change.

Am I just expecting too much from the system, or is something wrong? Should I swap the blue orifice tube for a white tube? Is it possible the smaller orifice in the blue tube is artificially increasing my high side pressures?

Let me know if there is any other info I can provide.

[phillipm]

I cannot add anything at the moment but it sounds like you did everything correct. I have pretty much the same system. Same compressor and everything. So far in Phoenix the best I've seen out of mine was 47*. I'm pretty much at the point of pulling it out and putting a new vintage air kit in. I know those work! However, I will watch this thread and hopefully someone can chime in.

[foamypirate]

Originally Posted by phillipm

I cannot add anything at the moment but it sounds like you did everything correct. I have pretty much the same system. Same compressor and everything. So far in Phoenix the best I've seen out of mine was 47*. I'm pretty much at the point of pulling it out and putting a new vintage air kit in. I know those work! However, I will watch this thread and hopefully someone can chime in.

Hah, I was actually considering the same thing!

Hopefully someone will have an "ah hah!" moment, and we'll figure something out.

[tucsonjwt]

I would review this thread on Vintage Air. My stock 83 C20 134A converted A6 compressor with a single Geo Metro pusher fan and stock condensor gets about 25 degrees at the a/c outlets. Unless you have very cold air coming out of the outlets a vehicle will never get cool in 100+ degree HotZona temperatures.

http://67-72chevytrucks.com/vboard/s...ight=tucsonjwt

[phillipm]

I've got a VA kit in my olds and my camaro. Both will do 38*-40* at the center outlet in 100*+ temps. Granted takes a bit to get down there that far but if they are setup right they are great. That's just my experience.
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[foamypirate]

Made a lot of progress today. We dropped the charge down to 26 oz, and things are WAAAY better. 90F, and even after extended idling, the high side was around 280-290 (still a bit higher than I'd like, but certainly better than 350-375). The HPCO no longer trips, even with about 1,500-1,800 RPM. The low side was 44-45. With the fan on max, and going down the road, I saw the vent temp dipping into the 46-48 degree range. Turning the fan speed down one notch resulted in 42 degree temps, and the clutch started to cycle. Once I finished my test loop, I popped the hood, and the whole accumulator was sweating, along with about 1 foot of rubber hose on the suction line off the accumulator. I think the charge is pretty much right on now. I might play with dropping the low pressure cut out just 1 or 2 psi to get that last little bit of cooling, being careful not to ice the evaporator, of course, but overall, MUCH happier with the system! I'm blown away by how small the charge is. I guess that PF condenser compared to the giant factory dual tube serpentine, and my shorter than factory hoses made quite a difference in system volume.

[phillipm]

That is definitely something you don't want to do with 134 is overcharge it. It's not happy when you do that. Sounds like our systems are performing very similar now! So when you get it down to 41-42 let me know so I can make those changes as well!