ALL, ALL, modern day automotive climate control systems, or more "simple" systems with automatic temperature setpoint control, operate the A/C cooling system 24/7, with a few exceptions, primarilly not below ~33F. The resulting system air outflow would be pretty discomforting were it not for the system's reheat/remix path, used to MODERATE the air outflow temperature to a level that only sustains , barely, the cabin atmosphere nearby your selected temperature setpoint.
....control

And that would be germane if you had a source of colder air than that inside your car when driving around when it is sunny and 100F outside...in which case, you would not need air conditioning.

...maybe a window airconditioner and a very long extension cord would do the trick.

The statement makes perfect sense. We are discussing potential sytems for pre '90 911s, not 2014 Lexus. They are somewhat different.

PM me your address, and I'll send you temp prove to stick in your vent. It seems you're either too poor to afford one, too scared to share the results, or maybe you don't even own a 911. If you can afford a prob, you have the knowledge to use it, and you own a 911 - then being a troll is the only other reason you wouldn't post this info.

Argument simply for the sake of argument...

If you don't understand then simply say so.

A good measure of an A/C system's cooling capacity relates to how different, how COLD, the outflow air will be vs the inlet air temperature at a specific airflow volume.

How cold will that room temperature, 72F, gallon of milk get for each minute left to chill in a 'frig...?

An idiot statement if I even saw one.

You and I both diverged from the current subject, pre '90 911s, to post 1990 products.

"..They are somewhat different.." Yes, different in the manner I stated, to which you jumped in and disagreed, falsely.

I think we have a winner.

I assume you wish to know my vent temps starting with the cabin preheated, fully preheated, HEAT soaked, to a specific temperature. Tell me which and if it is within reason I'll provide the initial vent temps, along with how long it takes the system to bring the cabin atmosphere down to 72F. I'll also provide you with the climatic conditions under which the test is run, OAT, Rh, and an estimate of the heat gain form the sun, if any.

Okay..?

blah-blah-blah,..no data testing points. Until that;s provided , you are dead in the water, WWEST. And I do mean truly dead. Quite tiresome with no test data.

Best,

Doyle

How many car owners with a stock AC system in a pre 1990 911/912/930 can say that?

Gentlemen, show of hands?

I am also an engineer...I suspect I understand as well as you...or better.

Explain why that is not the same as vent (outlet) temperature at a specific ambient temp (input) since the ductwork (air path) and evaporator fan are fixed (volume)?

If you don't understand, them simply say so.

Because ambient temperature, OAT, is NOT an input to the recirculate ONLY mode of the Porsche 911 pre-1990. While OAT does not change as a function of the duration of A/C operation, IAT does.

Evaporator fan are fixed (volume)...not in any of my 911s,

you, of all people, do not understand....?

The amount of cooling a given volume of air receives, temperature delta, upon each pass through the evaporator is a reliable measure of he system's cooling capacity.

Take the temps at whatever cabin and ambient you like. Just make sure to record what those temps are. We're not going to get a perfect lab setup, but knowing it's 85 degrees outside, high noon, sea level, 75% humidity, and the inside of the car is 90 degrees, well that will provide plenty of context. Take some vent temp readings when the inside is still steaming hot, and after it has cooled down. Make sure they're at idle.

LOL, nice. I don't believe wwest has any kind of science background. Or he does, and is TROLLING.

IAT does not change appreciably enough to make much difference...and is effectively OAT unless the vent temp is quite low and volume is quite high. If you start at 100F...a trickle of 65F air will not even overcome the engine heat and the sun coming through the windows. Most folks drive their 911s for an hour or two at most. The rate of change would never make a serious impact. If after 8 hrs of driving my 100F interior drops to 98F...I am not impressed.

The max volume of air is fixed on all my 911s. It is on yours as well.

Yeah, we've only been saying this for about ten threads now.

This doofus kills every damn AC thread there is by trying to shout down anyone who actually knows anything about these systems.

He's splitting hairs. The interior temp of the car is going to be much higher than the OAT, initially. 140-150 degrees F around here, in the summer. The big delta is opening the windows for a couple of minutes to get that super-heated air out, and to begin cooling all those IR-absorbing black materials in the car. All the while, the AC is running, and cooling the ductwork. Close up the car, turn the fan on high and let the Griff's evap fan blow hard on that higher-capacity evaporator. The interior temperature drops very nicely when the output air is 45 degrees at the highest air volume. Pretty soon, you have goosebumps and have to turn the air and the AC down a touch. The car is still at about 80 degrees, but the evaporative cooling on your skin is now in effect. And 80 is better than 140. Soon, the fan is at it's lowest speed, and the AC is set at the speed next to "off", and the air coming out of the vents is 35 degrees, and the interior temp is about 70, and steady.

He implies that vent temps are not important. Of course they are. It is not rocket science...I can park my two targas side by side at 95F ambient. Open the windows and IAT=OAT. One Targa has a 33F vent temp and the other 56F. One is comfortable almost immediately with the 33F air blowing on your body. Eventually you will begin to see some effect of the system cooling already cooled air. The other targa never gets comfortable. You can drive cross country and it will never cool down the interior if there are 100F+ temps. That is why vent temps are so important. If you can only drop IAT by a degree or 2 per hour...it is negligible unless you are driving cross country...and even then, it heats back up to ambient if you stop for gas.

When he specifically posts that he has tested his add-on fans and they will duplicate the performance posted above (which is what I would expect from an A/C system): "In 95F ambient air temp with full sun (over 300 shortwave insolation) system produces copious amounts of 40F air at high blower setting and a steady flow of 32F air at medium blower setting."...then he will be interesting. Until then...he is just tilting at windmills (and folks with well-designed, proved products). No one is looking for half a solution.