The Prius Experiment

[redpoint5]

Would an electric AC still use heat to achieve the right temperature? I'd think they would simply run the AC at a lower setting, or intermittently, to achieve temperature, not inject hot air.

[Blacktree]

Originally Posted by Drifter

Phase brought this up recently in his thread ( https://ecomodder.com/forum/showthre...tml#post666421 ), but using a higher temp setting usually uses more energy because most cars use the heater to warm the air conditioned air.

I didn't think about that. I was running the A/C at the highest temperature that was comfortable. I'll try a lower temperature with a lower fan speed, and see what happens.

Come to think of it, I remember the climate control automatically adding heat when I just wanted to circulate air (back when the weather was cooler). That was annoying, because using the heater made the gas engine run more often.

The climate control is not smarter than me. Gimme some freaking knobs! Also, get off my lawn! LOL

[Drifter]

Originally Posted by redpoint5

Would an electric AC still use heat to achieve the right temperature? I'd think they would simply run the AC at a lower setting, or intermittently, to achieve temperature, not inject hot air.

I would hope so - or that the heat is the last resort. If you have multi-zone A/C I don't see any other way than using the heat for the sections with higher temperatures.

I look forward to testing it this summer...

[Phase]

Originally Posted by ps2fixer

Temps up here in the extreme north (Michigan) are hitting 60's and in a few days it's going to the 80's, crazy how it went from basically just above freezing to boom middle of summer lol.

AC takes a lot of energy, not sure if much can be done to lower the load besides putting less cooling demand on it (higher temp setting). Pretty sure it's electric in your car, so it won't need to run the engine, but it's quite a draw on the hybrid battery.

If you have a grill block, you might see gains opening it back up some since the heat from the heat pump action of the AC system is pushed to the condenser up front

Another idea I just had, when you first get in the car, turning the AC on would help warm the engine up a little faster (heat pushed into radiator), but it's also likely will be loading the engine indirectly when still not up to operating temp. Couple ideas to play around with at least.

The steering wheel has an AC button, you can turn it on/off as needed, but I suspect the auto controls work fairly well at cycling the pump.

Must be nice. You’re more north than us and we are getting a foot of snow in one day here in Oregon. Gotta love May snowstorms lol

[Blacktree]

Meanwhile, here in Florida it's already in the 90s. It'll stay that way until late October / early November.

[ps2fixer]

Our summers in Michigan peak to around 90-100F, winter at night can get as low as -15F in my area, maybe -20F for the coldest night. General summer temps are mid to high 80's though. basically boarder line needing AC vs just windows down to get some air flow.

Every vehicle I've used in the past will cycle the AC pump on and off. The evaporator holds the boiling coolant, and when it's cold the ac pump isn't needed until it starts to warm up (liquid refrigerant all boiled into a gas) and the AC pump kicks back on. Low air flow would make the refrigerant boil away slower, max cold setting might run the AC pump more to keep it cooling at the most it can vs letting it cycle longer cycles. It makes no sense why it would add heat if the temp is set below interior temps, that's only used for defrost generally, ac to remove moisture, then heater core to warm up the air again. I could be wrong, the newer cars seem to do more dumb stuff, but I grew up in 80's to 90's vehicles and I mainly drive 90's era vehicles still. Simplest vehicles and generally pretty easy to work on and don't have a million extra things to go wrong. Then I have the unicorn, the 2006 prius lol.

Funny thing, I don't even know if my AC works in the prius. It seems to deforst the window when turned on, so pretty sure it at least has something for a charge.



@Phase We get some real weird weather here, it has snowed here with the air temps in the 40's maybe low 50's before. Today high was like 62F, low is 35F. Tomorrow says 69 high 40 low. We've had weeks where we are in the 80's and some days it's below freezing. Typical michigan weather, if it's sunny and nice out, you better do something outside before the weather decides to change lol.

Big thing in my area lately has been tons of wind. I'd say this has been the windiest year that I can remember. More wind storms than snow storms, the snow was really mild this year, didn't even need to snow blow the drive way. Year before I snow blowed it 3-4 times.

[Blacktree]

My very unscientific analysis seems to suggest max A/C with the fan at minimum speed didn't help. One day I ran the A/C set to 75 degrees, with the fan at medium speed. The next day, I ran it at max A/C with the fan at minimum speed. Both days, the average was about 54 mpg. Driving conditions were similar. Although it was not a controlled laboratory environment. So... grain of salt.

One note about running max A/C: I had to manually cycle the A/C on and off every few minutes. That was annoying. With the temperature set to 75, I just set it and forget it.

[ps2fixer]

It's pretty interesting AC is effecting your mpg quite a lot. I did some driving today with AC on, and got pretty similar to what I normally get. I set the temp to 75 and it seemed like a reasonable temp, I had family with me, so car had more weight, but more up town driving. Trip home I hit almost 50mpg driving 55mph with everything all warmed up and such with AC on.

Maybe your AC charge is low so it's running the pump more to get the same amount of cooling. It's not the perfect way of doing it, but getting a R134a refill kit and hooking it up with the gauge so you can see pressure should give a reasonable idea of how the charge is doing. If it's low, you might need to replace some o-rings and such. The instructions on the can/kit should say what the pressure should be for a given temp.

[hayden55]

Try again with the fan at 80-90% speed. This is what ECO mode does on the gen 3 Prius. It also runs the compressor a very mediocre way so it doesn't use as much power. Its hard to explain but it feels like you have a less effective ac pump with a noisy fan.
I some what helped my summer mpg by doing 70% crystalline on the windshield and 40% crystalline on the side windows. Math wise it blocks around 80% of the energy going through the windows with the stock tint.
I noticed for me when it is 90, full sun, and humid outside when i am traveling by interstate it would be at 80% bars on fan the entire interstate and i would still be a hot cold sweat. After the tint the fan ran around 40-60% bars and i felt more evenly to temp.
If i remember correctly the AC pump is 3500w or 4500w

[Phase]

Originally Posted by hayden55

Try again with the fan at 80-90% speed. This is what ECO mode does on the gen 3 Prius. It also runs the compressor a very mediocre way so it doesn't use as much power. Its hard to explain but it feels like you have a less effective ac pump with a noisy fan.
I some what helped my summer mpg by doing 70% crystalline on the windshield and 40% crystalline on the side windows. Math wise it blocks around 80% of the energy going through the windows with the stock tint.
I noticed for me when it is 90, full sun, and humid outside when i am traveling by interstate it would be at 80% bars on fan the entire interstate and i would still be a hot cold sweat. After the tint the fan ran around 40-60% bars and i felt more evenly to temp.
If i remember correctly the AC pump is 3500w or 4500w

Yikes crystalline. Should’ve gone with xpel Xr plus. I got 70 on my windshield and then normal darkness on the sides and I have a black car. Only need one minimum AC bar even when it’s over 100 degrees outside then sometimes it still gets too chilly inside and I have to point the vents away from me