Try setting your air conditioner like this.

I set it manually, but the use of recirc when you first get in a hot car is just wrong. It should be cooling outside air and purging the stale air in the cabin. Later, when inside is cooler than outside and the air is fresh, it should go to recirc to lessen the colling load.

I also found the higher fan better, and when I direct the vents towards me, I can set the temp much higher and maintain comfort.

To each his/her own, but the Auto behavior is usually wrong for me.

 

As you said, recirculation lessens the cooling load so that's why it's done first.

That stale air in the car is usually hot, so A/C works faster and more 'efficiently' by cooling the same air it's cooling inside the car than new air from outside. Just like how a fridge works.

Of course, it's probably more efficient to cool down all the heated insides first by just keeping the windows open before you turn on the A/C because even outside air is cooler than greenhouse heated insides.

I use auto, because the choices the Toyota engineers made make perfect sense to me albeit noisily. Only thing that bothers me is AC auto temp of 76 is not the same temperature as AC-off. So I have to set 77 AC-on, and 73 AC-off to get the same 'feel'.

This is my setting while it's 93F outside, and the vents directly toward the outsides of my face so it's not directly, but not indirectly either. I cool fine in direct sun..

 

"As you said, recirculation lessens the cooling load so that's why it's done first."

No, it doesn't if the inside temp is higher than the outside, which it is after a long day in the sun.

Example:
OAT = 80
IAT = 100
Desired temp = 75
Delta temp on recirc = 100 - 75 = 25 degrees
Delta temp on outside air = 80 - 75 = 5 degrees

Of course it takes less energy to cause a 5 degree drop than a 35 degree drop.

Most efficient cooling is to start with a window open, no recirc; then after a couple of minutes, I close the window, hit recirc.

 

KT,

I couldn't agree with you more. If it's 110 degrees in the car (we're both in SoCal, right) and 80 outside, it's got to be easier to cool the outside air. You don't need an HVAC degree to figure that out!

The "recirc" bothered me so much that I went to the dealer and had them reprogram the climate control so it doesn't default to "recirc" whenever you turn on the the A/C. I stays on "outside air" regardless of the temp inside or out.

Side Note; the first dealer I went to wanted $100 to do the reprogramming. The second I called offered to do it for free under warranty. Guess where I went?

DGStan

 

Here's the process I use when getting into the car (for what it's worth). This assumes that the A/C was left in Auto and set to desired temp. I should also note that I do not direct the air vents onto myself. My approach is to direct the outside vent airflow up and to the side of the car and the center vents up and along the center towards the back.

#1. Do NOT close the driver's door.

#2. As soon as seated execute a Power ON. (A/C will auto start in "recirc" mode and fan at a speed based on interior temp.)

#3. Roll down ALL windows. (If its really hot.)

#4. Fasten Seat Belt.

#5. Close Driver's door. (At this point the A/C will likely have flushed most of the hot air and you should feel some cooler air at the vents. Note: This will not be "ice cold" because, as in any A/C system, there is a maximum differential temperature that the A/C system is capable of producing.)

#6. Select direction and drive.

#7. Close ALL windows. (When this is done can be quite variable. It depends on how long it takes for the interior to "air out" and how loudly your partner screams about the wind messing up her/his hair. :cussing: )

Keep in mind that the A/C compressor and fan is totally battery driven and the ICE does not contribute at all to A/C operation. The one thing that does help is to get the car moving. This will increase the effective cooling by the A/C due to airflow across the condenser coils caused by the car's motion.

At some point the fan speed will automatically reduce and eventually the system will automatically switch out of "recirc" mode. (You can switch it out of "recirc" manually but IMO if you go through #1~5 then the air ducts should be fairly clear of the stale hot air.)

[hr:8bac743873]

He's my observations today after leaving the car setting in the direct sun for 2+ hours while I went to a movie.

• 
  
  It was ~92 degrees in San Jose today. Once the fan speed dropped to mid it remained there with an occasional return to High-2 (Mid+1) speed. The system never exited "recirc" mode.
  
  Unfortunately I didn't have a thermometer available to track the car's interior temp. It's probably going to be hot again tomorrow so I'll try the same thing with a thermometer to measure cabin temp and a instant thermometer that I can stick into the air vent to measure the exhaust temp.

 

Look, we're saying the same thing. I'm saying that depending on the temperature difference between outside the car and inside, it's more efficient to cool the car ai by recirc with closed windows like say when you're on the freeway or something.

Lemme illustrate:
air to cool: 100F (I)
desired temp: 75F
air source to cool (outside): 90F (O)
air source to cool (recirc): decreasing from 100F ®

Say the AC (A) coils can cool any air passing over it down 20F in 1 microt. So O passing through will come out 70F in the first microt (Ao), and R coming through will be 80F (Ar). Car air volume is (Cv) @ 5m^3, and vent air volume is (Vv) @ 1m^3.

So, standard air temperature mixing formula is (I*Cv + A*Vv) / (Cv + Vv), or weighted average.

So in the first microt for Io' it's: (100F*5 + 70F*1) / (5 + 1) = 95F
First microt for Ir' is: (100F*5 + 80F*1) / 5 + 1) = 96.6F

So what happens?:
....Io......Ir.....Ao..Ar
0: 100F 100F 70F 80F
1: 95.0 96.7 70 76.7
2: 90.8 93.3 70 73.3
3: 87.4 90.0 70 70.0
4: 84.5 86.7 70 66.7
5: 82.1 83.3 70 63.3
6: 80.0 80.0 70 60.0
7: 78.4 76.7 70 56.7
8: 75.8 73.3 70 53.3
9: 74.8 66.7 70 50.0

Recirc beats outside to 75F by ~2 microts even though it seems hotter in the beginning. Recirc wins because Ao can cool only by a constant, whereas recirc 'snowballs'.

Of course, the result is highly dependant on O not being significantly cooler than what the AC can cool it by (Ar). So if outside air is 80F, recirc is 3 microts slower, and so it loses as per your original example.

So if it's much cooler outside, use outside air, but if the outside air is like 90F, recirc is much faster in this closed system.

Now 'opening' the system is of course just open the windows, and it has a lot more air cooling volume than the vents to get things down to ambient room temperature. Recirc can then take it from there, as how you do it.

Personally, I keep the fan system OFF (instead of recirc or normal) with the windows open because vent air is still hot at first anyways. ~5-10 minutes later I hit auto, and 2 minutes later close all windows.

YMMV