Sorry for the late response, been real busy recently so haven't gotten much work done on the 80. Ended up replacing expansion valve and recharging. After driving around and then hooking up gauges, low side read 30 and high side 210 at idle with ambient temp at condenser of around 85 degrees. When sitting at idle, vent temps hover around 60. In stop and go traffic, it'll dip in the mid to low 50's and driving fast has gotten me as low and 42. That's in cloudy weather with temps in the mid to high 80's. I still feel like something is off though because 60 degrees at the vent at idle seems kind of high and it takes a while for it to get down into the 40's.
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Knowing what I do about the 80 series A/C system I would say there is probably a 'little' more to be had...but not a lot.
Ultimately...it is going to come down to whether or not you are comfortable at those vent temps. IF you are...then chasing numbers is not going to be worth the return. IF you are NOT comfortable at those temps...then we need to look at two things:
1. The exact procedure you used to pump down the system and recharge it (many possible pitfalls there).
2. Ways to improve air flow across your condenser (Fan Clutch Mod and Aux Fan).
I will say that your current pressure readings are spot on for the ambient temp cited....but there are so many things we don't know about the recharging of the system. Excess oil in the system will effect the overall cooling capability, air in the system (if you didn't purge your lines, or shut off the manifold lines before shutting off the pump, didn't evacuate the system long enough, didn't use new vacuum pump oil or the wrong oil...etc, etc). All these things and more can make the difference when trying to get peak performance from the system.
You and I live in areas of High Humidity and that is your chief source of discomfort. Naturally we will want an A/C system that will cool the interior as quickly as is possible. How 'possible' that is....is dependent on the heat load at any given time (ambient temp, humidity, solar gain, cabin temp at start up).
Thankfully the 80 series uses a pretty good blower motor (OEM) and an adequately sized Evaporator. They are sufficient to service the first two rows of the vehicle pretty well (if all is working correctly). But the OEM system uses a Serpentine condenser (not as efficient as more modern parallel flow)...so that is what it is.
EVERY A/C system works by removing heat and moisture from the cabin air, this is an important fact to remember. Your A/C system (not unlike your cooling system) is big heat exchanger. So...the faster we can achieve this exchange of heat, the quicker we can reduce cabin temperatures.
Assuming a proper refrigerant charge (and little to no contaminants) then AIR FLOW is what we are after.
Air flow is your friend.
We need air flow inside the cabin and air flow through the condenser. Air flow in the cabin is strictly a product of the blower motor, so a finite amount of air there. BTW I would advise everyone to drop the blower from time to time and clean the fan/wheel (some are amazingly dirty, clogged). As for the condenser, there are improvements that can be made there.
IMO, air flow into and out of the engine compartment of an 80 series is abysmal at speeds that don't create 'ram air' and even then...I consider the engine and cooling system to be 'fan dependent' when ambient temps are high.
Doing the Fan Clutch Mod will help move air across/through both your condenser (first in line) and your radiator (next in line). Also... adding an Aux Fan (for the condenser) is a proven aid for low speed performance of the A/C.
IF you have the means to do the following....we can semi-assess what measures you might wish to take:
Hook up manifold gauges, start engine, set A/C to coolest setting, blower on high, recirculate, windows up, engine at idle. Some sort of temp measuring device for vent temps.
Let the system run for 8-10 minutes to stabilize. Record the center vent temp and pressure readings.
Now take a hose and lightly 'mist' the condenser for 4-5 minutes. Watch the pressure readings to see if they fairly rapidly reduce and then check your center vent temp. Also, note IF your compressor cycles at anytime during this test (it probably will).
IF vent temps decrease along with manifold pressure and your compressor cycles sometime during this... then your system is most likely OK (even if not optimal) and I would look to improving Air Flow in order to get all that you can from the system .
But ultimately its each person's 'call' with respect to how much work they are willing to do. I always advise against 'chasing specific numbers'. Conditions are too variable to say that YOUR system isn't working correctly because you don't have the same numbers as mine. Vent temps that are 30°F below ambient are pretty good and is all that should be expected. Anything more (is sometimes possible) and all the better.
