Any idea into the brain of the AC?

[Cobb]

Ive been using the auto feature of the ac and trying to better understand it.

From most econ cars I have owned, it seems to blow colder under acceleration vs driving at a steady speed. Most econ cars cut the ac under acceleration.

Not too unexpected but you do get a colder blast from coasting and braking.

I almost wonder if it has a larger than normal accumulator. It seems to store freon under pressure and can give cool air while the compresor is off. I notice parked under the hood you can hear something under pressure leaking down near the passengers side.

Another interesting note is that it can keep you from sweating, but still make the cabin feel warm. I have to admit I miss feeling like I am in a meat freezer if not see frost on the outside of the windows and your glasses when you open the door.

Once the cabin is to temp, I am finding I need it on 68 degrees to keep my passengers comfortable and a steady breeze. I try 72 or higher and it seems to have a mind of its own and cutting off and on.

[RahTX]

Sorry I can't give any technical insight (no pun intended), but when the temps hit 90+ here, which they are already beginning to do, I've given up on letting the A/C decide for me with auto, and set it manually (Lowest temp, A/C on, fan speed 2-4, recycle cabin air).

If I'm in the car alone and can sweat it out, I'll let it do it's thing, but when my Mom, for example, is in the car, I take ECON off and put it in Sport mode to avoid auto-stop and A/C cut off. She's very picky about temperature and I'm pretty sure she would disown me if I let her endure that for the sake of MPG

[Cobb]

WHAT!!!!!!! People and or family members are giving you dirty looks too because they cant wear a jacket in the car with you during the summer???

Yeah, I may have to do that too. Seems ice creme will melt in the hour trip to home from the store. Looks like I have to start carrying the cooler or doing what you are doing.

[KlumzyDriver]

I can "live" with the 72 degree setting or I could even set it slightly higher than that- but I would only want to do this if I knew to do so was more efficient and would ultimately save gas. What frustrates me is I can't seem to figure out is what is the most energy efficient way and also the most FRUGAL way to use the AC in this car.

For instance if we knew that air temperature was moderated (for higher temperature settings) by warming air after it FIRST had been cooled to the maximum extent possible, we then would all realize there is no efficiency gained by setting the thermostat higher. In fact, if the intent is to cool, then warming air you just previously expended energy to cool is most in-efficient, but I think that is precisely how most automobiles moderate air conditioned temperatures.

It would then seem the most efficient temperature setting would be the coldest thermostat setting. The fan speed setting would then be used to adjust the temperature of the car to the extent possible while maintaining the efficiency.

But would this save gas in the long run? Or would the coolest thermostat setting force the compressor to run more, thus actually making the most efficient setting also the least frugal?

[pikkashoe]

I too have been wondering about the AC system. Im trying to figure out if setting a lower temperature lowers mpg vs setting a higher temp. Im starting to believe setting it higher has no effect on mpg. Also trying to figure out if the fan speed effects mpg. Is a higher fan speed going to cause lower mpg, or does the fan not effect mpg since it seems to run of the electric system only (when engine shuts off, fan still keeps the same air flow, just the ac stops cooling).

[Cobb]

In general, most cars ac systems use the high pressure switch to signal it to cycle off. So, instead of mixing heat with the cold air, it would be most efficient to set to lowest setting so it stays off more than on as to the built up of freon in the high pressure side.

Some econ cars turn off the ac compressor under wot by a switch under the gas petal.

Anyway, I have done the ac on lowest setting and the auto setup. Seems on the auto setup I take less of a hit in fuel economy.

Ive notice in auto stop that it still seems to blow cold air before it fades to warm vs other cars. I was wondering if the high side had a larger than normal reciever/dryer to allow this extra storage.

2nd, it seems to blow more cold air when accelerating in the blue color. I dont know if the ac is working harder cause you are driving in efficiently or higher rpms of the motor making more cold freon.

Now, same with decelerating, it seems to too give a burst of cold air.

I think some of the gen 1 guys use braking and coasting to turn the ac on full blast to get free cold air. That seems possible to have it cycle the compressor during coasting and braking to save power.

[pikkashoe]

When you say lowest setting, Im assuming you mean the lowest (coldest temp) right?
So basically your saying the best way you have seen it to run the AC in automode?

[buglermcd]

The only known way to save gas with the AC is to use ECON ON. This will make the compressor cycle less often.

If you really want to find out what is the most efficient way, you'll have to be a bit wasteful.

Just park the car and have it running and turn on the AC to the coldest setting. Make sure the cabin temp stabilizes. This will probably take a good 10 minutes of running the car, just sitting there.

Go outside and listen to how often the compressor kicks in. Note however many times/minute it klicks on.

Then, turn the Auto gauge up to 75 or so. Wait about 10 minutes so the temp stabilizes. Step back outside and see how many times the compressor kicks in.

If the compressor kicks in less often with the higher temperature, then you'll probably use less gas. If it's running the same amount of time, then it's warming the air up after it's been cooled.

If it's warming the air up after the fact, then always keep it on the lowest setting, and just cklick the AC button off whenever you get too cold (Be sure to also hit the recirculate button to recirculate the already cold air, instead of bringing in how air). And always click it on when coasting/braking.