Fuel Economy and Auto temp control

[Nliiitend1]

The MS3 is drive-by-wire. There is no physical connection between the accelerator pedal and the throttle plate.

 

[dan1101]

The MS3 is drive-by-wire. There is no physical connection between the accelerator pedal and the throttle plate.

Aww, that's gonna bug me now!

 

[BillTheCat]

I wonder if someone with dashhawk can post engine load numbers from having the AC on, off, auto climate on/off and various vent positions and settings.

Good suggestion. This weekend, I'll go for a highway cruise. Set cruise control for constant speed, and then read load info off DH with A/C on & off, and fan at min, max, and off. Vent selections shouldn't make a difference, and I suspect fan speed won't either, but I'll try them anyhow, in case the vent selections actually trigger A/C without the light coming on.... but I swear I have hit the defroster & thrown warm, moist air at the windshield before, then watched it dry up when I select the A/C button.

I'll try a number of combinations & try to keep a record as I drive. Might need to just use a voice recorder for this if I cannot find a passenger to take notes.

 

[dan1101]

Good idea, should have some nice flat highways in Florida. No such thing here in VA.

 

[AWDthis]

Yeah I would love to find the diff. in MPG with the AC on in low fan speed vs auto, I usually drive with my windows down all the time, low fan if its realllllyyyy hot, but if Auto makes no diff, id rock that all the time let us know BillTheCat

 

[eg6motion]

Hit the auto button, it handles everything automatically. But you can then manually select the fan speed and/or vent pattern and the temperature remains auto, as far as I can tell. I ran that way all last summer and winter and didn't notice it freezing or boiling me.

once you adjust anything then it comes off the auto setting. At that point you are simply adjusting your heat range as though you are in a car without climate control. There are no individual auto adjustments.

 

[dan1101]

once you adjust anything then it comes off the auto setting. At that point you are simply adjusting your heat range as though you are in a car without climate control. There are no individual auto adjustments.

I leave mine set at 69 and it stays 69, so I'd consider that auto temperature. Not sure about fan.

 

[Nliiitend1]

once you adjust anything then it comes off the auto setting. At that point you are simply adjusting your heat range as though you are in a car without climate control. There are no individual auto adjustments.

This is incorrect.

Once you adjust something manually, only the thing you adjust becomes manually controlled. Each setting gets "unautomated" separately. If you adjust everything manually, then everything gets put into "manual" mode, but if you adjust say, only the fan speed, then the temp, vent settings, and recirc mode on/off stay in auto mode.

 

[eg6motion]

This is incorrect.

Once you adjust something manually, only the thing you adjust becomes manually controlled. Each setting gets "unautomated" separately. If you adjust everything manually, then everything gets put into "manual" mode, but if you adjust say, only the fan speed, then the temp, vent settings, and recirc mode on/off stay in auto mode.

That is not correct. Per the car's manual, everything is manually controlled when the "AUTO" indicator light is off. As per MPG, the AC light may stay illuminated even when the AC compressor is not actually running....this is also in the manual. So when the AUTO indicator is off, you are only selecting the desired air-flow temperature of the heating system, not the desired temperature of the interior. If your car is 40 degrees inside, you set the fan on low and temp at 69, your car's interior will not reach 69. If you set the fan to max then your interior will likely get warmer than 69. The only automatic function to keep your interior at 69 is to enable the climate control switch which will illuminate the "AUTO" light. This is all in the manual...

When the light goes off, the last settings the system used remain current...but their is no automation. Cranking your fan on high at the same airflow temp means your car will get much hotter, and there will be no intervention or change in vents, airflow temp, fan temp, recirc, etc....its all manually controlled if you change anything.

 

[Nliiitend1]

You're misunderstanding the manual...

Quoted from the manual (referring to the AUTO indicator light):

"When off, it indicates the operation of other switches such as the mode selector switch, fan control dial, A/C switch and windshield defroster switch. Other functions will continue to operate automatically."

 

[eg6motion]

You're misunderstanding the manual...

Quoted from the manual (referring to the AUTO indicator light):

"When off, it indicates the operation of other switches such as the mode selector switch, fan control dial, A/C switch and windshield defroster switch. Other functions will continue to operate automatically."

you do understand the only other function is the temperature dial correct? And yes, it will automatically stay the same (as the car will unlikely randomly change temperatures on you as it doesn't have hands). But it still no longer has a bearing on your interior temperature...its simply the desired airflow-temp...thats on the next page of the manual.

 

[Nliiitend1]

The statement quoted above is saying that when the light is off, at least one of those things has been manually adjusted, not necessarily all of them...

When something gets manually adjusted, the climate control simply does its best with the parameters still under its control to achieve the desired temp (the temp indicated on the display).

 

[dan1101]

Yeah I just tested this on a 20 minute drive. I hit Auto, that of course turned on the AC and defrost, fan up to level 3. Then I changed the vents to Middle/Floor, and hit the A/C button to turn it off. That of course turned the Auto light off. As I drove and the car warmed up, the fan by itself went down to level 2, then level 1 after 15 min or so.

So basically the Auto light is only lit when all the climate control is automatic.

 

[Nliiitend1]

Yeah I just tested this on a 20 minute drive. I hit Auto, that of course turned on the AC and defrost, fan up to level 3. Then I changed the vents to Middle/Floor, and hit the A/C button to turn it off. That of course turned the Auto light off. As I drove and the car warmed up, the fan by itself went down to level 2, then level 1 after 15 min or so.

So basically the Auto light is only lit when all the climate control is automatic.

Correct.

 

[BillTheCat]

I didn't run a full test yet- that'll come later today. But as I drove to work last night, I did toggle the A/C on & off a number of times. Always keeping on a straight stretch of highway, with a nearly level grade (this is Florida, almost every road is on a level grade). It would appear that at highway speeds, about 75mph, with a base engine load of 30%, activating the A/C increases the load by about 2%.

For the purpose of actually measuring changes in load, it'd be more helpful if the DH could display .1% increments, but since it doesn't, this is the best I can do. A/C off, load would toggle between 30/31%. Turn on fan only, no change, regardless of speed setting, as expected. Turn on A/C, and the load toggled between 32/33%. Net- about 2%.

I'll do some more testing on a pleasure cruise later today...

 

[AWDthis]

Your saying that when you hit Auto the load was 2% higher or when you just turn on the A/C at low speed?

 

[robin2660]

You know, you don't have to go through the complication of logging test drives and interpolating the data.

How about just having the car running, parked, and listen for the compressor to kick in while observing the controls? Enlist the help of a friend, if necessary.

KISS

 

[dan1101]

You know, you don't have to go through the complication of logging test drives and interpolating the data.

How about just having the car running, parked, and listen for the compressor to kick in while observing the controls? Enlist the help of a friend, if necessary.

Yeah that would be a good thing to measure, but the efficiency may be different while driving.

 

[BillTheCat]

Your saying that when you hit Auto the load was 2% higher or when you just turn on the A/C at low speed?

I never hit "Auto." I manually turned on the fan, changed fan speeds, turned the A/C on & off, etc. Only difference in load was with A/C on, about +2%.

Mind you, all of my "testing" was done at ~75mph/3k RPM, typical everyday highway conditions.

I did go back out & tinker with the defroster. I started with the fan blowing to the main vents, but no A/C. And when I turned on the defroster, the load increased by the same 2% as when I manually turn on the A/C, even though the A/C indicator remains off. Toggle back to the main vents, load decreases 2% again. Toggle to the bi-level defrost/foot vents, and load goes up 2%. Toggle back to bi-level main/foot vents, load goes back down 2%. Looks like any time you direct air to the windshield, you get A/C, which is actually the most effective way to defrost the glass, anyhow, so it saves me the trouble of pressing another button.

So, I was incorrect about the defroster not overriding your A/C selection. One thing I did not think to do was press the A/C button a few times while in defrost mode to see if I could force it to turn the A/C off during defrost. (Mind you, no frost here in FL), but the test still applies.

And yeah, I coulda tested this in the driveway, but it's more fun to go for a frakkin' drive!!! (drive)

 

[dan1101]

Interesting, ok that seems to match what we concluded before. I think the only positions that don't turn on the AC are "floor and vents", and "vent only". "Floor only" turns on the AC for some reason.

If the damn software was considerate of us control freaks, it would light the AC indicator whenever the AC was on.