How does AC affect power and gas mileage
#1
10-19-2008, 02:24 AM
How does AC affect power and gas mileage
I'm pretty sure this was answered somewhere buried in the threads but I can't find it.
When I use the defrost, I can hear the AC kick in. This is very annoying cause i only want air blowing through the vent. If I leave it in this setting, how does this affect my mileage and power.
I'm constantly switching from "front and foot" setting to defrost.
When I use the defrost, I can hear the AC kick in. This is very annoying cause i only want air blowing through the vent. If I leave it in this setting, how does this affect my mileage and power.
I'm constantly switching from "front and foot" setting to defrost.
#2
10-19-2008, 03:16 AM
I'm pretty sure this was answered somewhere buried in the threads but I can't find it.
When I use the defrost, I can hear the AC kick in. This is very annoying cause i only want air blowing through the vent. If I leave it in this setting, how does this affect my mileage and power.
I'm constantly switching from "front and foot" setting to defrost.
When I use the defrost, I can hear the AC kick in. This is very annoying cause i only want air blowing through the vent. If I leave it in this setting, how does this affect my mileage and power.
I'm constantly switching from "front and foot" setting to defrost.
#3
10-19-2008, 08:51 AM
And I would be willing to bet that the amount of extra fuel it uses is so minute you would hardly see it in a calculated comparison of running one tank with it and one without it (I could be wrong so prove me wrong if anyone does have the calculations). AC Compressors in newer cars are extremely efficient compared to ones of yesteryear. Also keep in mind that if it is warm outside running the AC will provide better fuel economy than rolling down windows as rolling down windows creates a parachute effect destroying aerodynamics.
Almost all new cars engage the AC when on defrost and that is the best way to use defrost. AC does not mean "cold" air. The air is also stripped of it's humidity which is what contributes to iced or fogged windows, stripping out the humidity means the windows clear much faster than without.
Almost all new cars engage the AC when on defrost and that is the best way to use defrost. AC does not mean "cold" air. The air is also stripped of it's humidity which is what contributes to iced or fogged windows, stripping out the humidity means the windows clear much faster than without.
#4
10-19-2008, 09:26 AM
Almost all cars equiped with a/c have a system pressure switch that when it's cold outside will prevent the a/c compressor from running. I think it cuts out the a/c compressor around 30 deg F.
#5
10-19-2008, 02:03 PM
Does the Fit not have a hack (like the Civic) where you can have the option of turning the A/C off with the defrost? I use defrost most of the time and this will bug me if I can't change it...
FYI, here is the Civic one: (works fine for 7th gen & 8th gen)
1. Turn car on.
2. Turn temperature knob all the way cold and turn the fan knob to off.
3. Put vent location to "face"
4. Turn car off
5. Hold down the Recirculation Button and the A/C Button.
6. Hold down both buttons and turn the key all the way to the on position.
7. Keep both buttons depressed until one of the lights blink a few times, then you get a solid green light once the change has been made. Then let go.
8. See if it works by putting the fan on in Defrost You should see the A/C light turn on and you should be able to turn it off.
FYI, here is the Civic one: (works fine for 7th gen & 8th gen)
1. Turn car on.
2. Turn temperature knob all the way cold and turn the fan knob to off.
3. Put vent location to "face"
4. Turn car off
5. Hold down the Recirculation Button and the A/C Button.
6. Hold down both buttons and turn the key all the way to the on position.
7. Keep both buttons depressed until one of the lights blink a few times, then you get a solid green light once the change has been made. Then let go.
8. See if it works by putting the fan on in Defrost You should see the A/C light turn on and you should be able to turn it off.
Last edited by StewPiddass; 10-19-2008 at 02:21 PM.
#6
10-19-2008, 02:20 PM
Almost all new cars engage the AC when on defrost and that is the best way to use defrost. AC does not mean "cold" air. The air is also stripped of it's humidity which is what contributes to iced or fogged windows, stripping out the humidity means the windows clear much faster than without.
It probably is the best way to defrost however it would be nice if i could control it myself. I mean the button is right there. You mention the gas mileage difference is minute, but does it take away power when driving (or is that minute too)?
#7
10-19-2008, 02:22 PM
TURNED MY HEAT ON FOR THE FIRST TIME TODAY AND SURE ENOUGH THE A/C KICKED ON..O MAN...NOTICED A/C LIGHT WAS ON. TURNED OFF A/C ...ALL WAS GOOD.
ALSO WITH DRIVER WINDOW DOWN, RIGHT REAR DOWN 1/2 AND LEFT REAR DOWN 2 INCHES @ 60 MPH AND NO A/C, TRIP COMPUTER WENT FROM 45 TO 48.3 ON THE SAME 32 MILE TRIP.
THE WINDOW SETTINGS WERE PICKED DUE TO THE MOST AIRFLOW WITH THE LEAST NOISE AND EAR PRESSURE...THUNDER...YOUR MILAGE MAY VARY
ALSO WITH DRIVER WINDOW DOWN, RIGHT REAR DOWN 1/2 AND LEFT REAR DOWN 2 INCHES @ 60 MPH AND NO A/C, TRIP COMPUTER WENT FROM 45 TO 48.3 ON THE SAME 32 MILE TRIP.
THE WINDOW SETTINGS WERE PICKED DUE TO THE MOST AIRFLOW WITH THE LEAST NOISE AND EAR PRESSURE...THUNDER...YOUR MILAGE MAY VARY
#8
10-19-2008, 02:23 PM
Some guys on the Civic forum (with Si's) have reported getting an extra 80 miles to a tank after doing the hack...
#9
10-19-2008, 03:42 PM
Per Consumer Reports' testing on things that affect gas mileage...
"Air conditioning vs. opening windows. Some people advise you not to run the air conditioner because it puts more of a load on the engine, which can decrease fuel economy. But others say that opening the windows at highway speeds can affect gas mileage even more by disrupting the vehicle's aerodynamics. Our tests show that neither makes enough of a difference to worry about. Using air conditioning while driving at 65 mph reduced the Camry's gas mileage by about 1 mpg. The effect of opening the windows at 65 mph was not even measurable."
"Air conditioning vs. opening windows. Some people advise you not to run the air conditioner because it puts more of a load on the engine, which can decrease fuel economy. But others say that opening the windows at highway speeds can affect gas mileage even more by disrupting the vehicle's aerodynamics. Our tests show that neither makes enough of a difference to worry about. Using air conditioning while driving at 65 mph reduced the Camry's gas mileage by about 1 mpg. The effect of opening the windows at 65 mph was not even measurable."
#10
10-19-2008, 04:06 PM
Does the Fit not have a hack (like the Civic) where you can have the option of turning the A/C off with the defrost? I use defrost most of the time and this will bug me if I can't change it...
FYI, here is the Civic one: (works fine for 7th gen & 8th gen)
1. Turn car on.
2. Turn temperature knob all the way cold and turn the fan knob to off.
3. Put vent location to "face"
4. Turn car off
5. Hold down the Recirculation Button and the A/C Button.
6. Hold down both buttons and turn the key all the way to the on position.
7. Keep both buttons depressed until one of the lights blink a few times, then you get a solid green light once the change has been made. Then let go.
8. See if it works by putting the fan on in Defrost You should see the A/C light turn on and you should be able to turn it off.
FYI, here is the Civic one: (works fine for 7th gen & 8th gen)
1. Turn car on.
2. Turn temperature knob all the way cold and turn the fan knob to off.
3. Put vent location to "face"
4. Turn car off
5. Hold down the Recirculation Button and the A/C Button.
6. Hold down both buttons and turn the key all the way to the on position.
7. Keep both buttons depressed until one of the lights blink a few times, then you get a solid green light once the change has been made. Then let go.
8. See if it works by putting the fan on in Defrost You should see the A/C light turn on and you should be able to turn it off.
I then proceeded to my 2004 Odyssey, did the same procedure and it worked also (this time with the button going alternatively blinking then solid green).
Thanks a million, that's awesome!!!!
#11
10-19-2008, 05:08 PM
There's definitely a tangible effect on power. When we drove through the mountains in the summer, we really struggled on the uphill sections. The only way to keep up with traffic was to trade the AC for the few extra horsepower. With the AC on, we were bleeding speed up the hill with the pedal to the floor.
#12
10-19-2008, 06:14 PM
Absolutely awesome. It worked on my 09 Fit Sport AT. There is no Recirculation button, but I just set it to Recirculate, then it does not flash nor does it go into solid green. Just held for about 10 seconds. Then it worked!!
I then proceeded to my 2004 Odyssey, did the same procedure and it worked also (this time with the button going alternatively blinking then solid green).
Thanks a million, that's awesome!!!!
I then proceeded to my 2004 Odyssey, did the same procedure and it worked also (this time with the button going alternatively blinking then solid green).
Thanks a million, that's awesome!!!!
- car on, temp to cold, fan off, vent to face, car off
- held onto the A/C button, no recirculate button but left on recirculate
- car on and held button for 10-15 seconds, let go
when i put it in defrost mode with fan setting to 1, i hear the compressor go on for about 8 seconds, then off for 10 secs, then back on for 8 seconds. If I put it on 'face' setting and manually turning on AC, same pattern. Whats wrong?
question: was ur AC button on or off before you held onto it?
#14
10-20-2008, 03:27 PM
TURNED MY HEAT ON FOR THE FIRST TIME TODAY AND SURE ENOUGH THE A/C KICKED ON..O MAN...NOTICED A/C LIGHT WAS ON. TURNED OFF A/C ...ALL WAS GOOD.
ALSO WITH DRIVER WINDOW DOWN, RIGHT REAR DOWN 1/2 AND LEFT REAR DOWN 2 INCHES @ 60 MPH AND NO A/C, TRIP COMPUTER WENT FROM 45 TO 48.3 ON THE SAME 32 MILE TRIP.
THE WINDOW SETTINGS WERE PICKED DUE TO THE MOST AIRFLOW WITH THE LEAST NOISE AND EAR PRESSURE...THUNDER...YOUR MILAGE MAY VARY
ALSO WITH DRIVER WINDOW DOWN, RIGHT REAR DOWN 1/2 AND LEFT REAR DOWN 2 INCHES @ 60 MPH AND NO A/C, TRIP COMPUTER WENT FROM 45 TO 48.3 ON THE SAME 32 MILE TRIP.
THE WINDOW SETTINGS WERE PICKED DUE TO THE MOST AIRFLOW WITH THE LEAST NOISE AND EAR PRESSURE...THUNDER...YOUR MILAGE MAY VARY
But yea I have the hack done too. Some times you really need the AC on cause the fog just wont go away. Also something good to remember, the most fuel efficient way to run AC, is to run it on recirculation and coldest, then adjust the fan. If you do it that way and set the fan on low the AC will cycle on and off. On the lowest fan setting this way the compressor will kick on for about 10 seconds and off for 30, which will in turn save you gas. I usually crank the AC for a while then when it gets cold I turn down the fan. Just remember this for the summer.
#16
10-22-2008, 08:28 AM
Does the Fit not have a hack (like the Civic) where you can have the option of turning the A/C off with the defrost? I use defrost most of the time and this will bug me if I can't change it...
FYI, here is the Civic one: (works fine for 7th gen & 8th gen)
1. Turn car on.
2. Turn temperature knob all the way cold and turn the fan knob to off.
3. Put vent location to "face"
4. Turn car off
5. Hold down the Recirculation Button and the A/C Button.
6. Hold down both buttons and turn the key all the way to the on position.
7. Keep both buttons depressed until one of the lights blink a few times, then you get a solid green light once the change has been made. Then let go.
8. See if it works by putting the fan on in Defrost You should see the A/C light turn on and you should be able to turn it off.
FYI, here is the Civic one: (works fine for 7th gen & 8th gen)
1. Turn car on.
2. Turn temperature knob all the way cold and turn the fan knob to off.
3. Put vent location to "face"
4. Turn car off
5. Hold down the Recirculation Button and the A/C Button.
6. Hold down both buttons and turn the key all the way to the on position.
7. Keep both buttons depressed until one of the lights blink a few times, then you get a solid green light once the change has been made. Then let go.
8. See if it works by putting the fan on in Defrost You should see the A/C light turn on and you should be able to turn it off.
#17
10-22-2008, 10:02 AM
Does the Fit not have a hack (like the Civic) where you can have the option of turning the A/C off with the defrost? I use defrost most of the time and this will bug me if I can't change it...
FYI, here is the Civic one: (works fine for 7th gen & 8th gen)
1. Turn car on.
2. Turn temperature knob all the way cold and turn the fan knob to off.
3. Put vent location to "face"
4. Turn car off
5. Hold down the Recirculation Button and the A/C Button.
6. Hold down both buttons and turn the key all the way to the on position.
7. Keep both buttons depressed until one of the lights blink a few times, then you get a solid green light once the change has been made. Then let go.
8. See if it works by putting the fan on in Defrost You should see the A/C light turn on and you should be able to turn it off.
FYI, here is the Civic one: (works fine for 7th gen & 8th gen)
1. Turn car on.
2. Turn temperature knob all the way cold and turn the fan knob to off.
3. Put vent location to "face"
4. Turn car off
5. Hold down the Recirculation Button and the A/C Button.
6. Hold down both buttons and turn the key all the way to the on position.
7. Keep both buttons depressed until one of the lights blink a few times, then you get a solid green light once the change has been made. Then let go.
8. See if it works by putting the fan on in Defrost You should see the A/C light turn on and you should be able to turn it off.
#18
10-22-2008, 11:37 AM
FWIW...
From Edmunds.com:
We Test the Tips
The Mythbusters also address this question in episodes 22 & 38. 22 found the AC on, windows up scenario to be more efficient. But when they revisited this question they found a flaw in the original results. The final outcome, as reported in episode 38, was that AC on & windows up was more efficient above 50 mph, but ac off, windows down was more efficient below 50 mph.
My own, personal, test show no measurable difference (tested on several vehicles from a 300 hp V8 Lincoln Navigator to my current FIT) and AC on is much more comfortable.
The only car that I have ever owned that suffered from power loss when the AC was on, was a 1972 Chevy Vega, and it was a serious piece of crap.
From Edmunds.com:
Test #4 A/C On, Windows Up vs. A/C Off, Windows Down
This has got to take you back to the days with the family on vacation. Dad says, "Turn the A/C off! It wastes gas!" And Mom says, "We can't roll the windows down or everyone on the highway will think we can't afford A/C." And you're in the back roasting, hoping someone will win the argument so you can cool off.
Well, family psychology aside, if dads are still saying this, they aren't necessarily right. While the A/C compressor does pull power from the engine wasting some gas, the effect appears to be fairly minimal in modern cars. And putting the windows down tends to increase drag on most cars, canceling out any measurable gain from turning the A/C off. But this one depends on the model you're driving. When we opened the sunroof in our SUV, the mileage did decrease even with the A/C off. Still, in our experience, it's not worth the argument because you won't save a lot of gas either way. So just do what's comfortable.
Method: We drove the full 55 mile-loop in two cars at equal speeds both times — 65 mph. The first loop we drove with the A/C on and the windows up. The second loop we drove with the A/C off and windows down. In the second test we drove 20-mile loops. This was far enough to see our gas mileage level off and remain steady on the computer trip meter.
This has got to take you back to the days with the family on vacation. Dad says, "Turn the A/C off! It wastes gas!" And Mom says, "We can't roll the windows down or everyone on the highway will think we can't afford A/C." And you're in the back roasting, hoping someone will win the argument so you can cool off.
Well, family psychology aside, if dads are still saying this, they aren't necessarily right. While the A/C compressor does pull power from the engine wasting some gas, the effect appears to be fairly minimal in modern cars. And putting the windows down tends to increase drag on most cars, canceling out any measurable gain from turning the A/C off. But this one depends on the model you're driving. When we opened the sunroof in our SUV, the mileage did decrease even with the A/C off. Still, in our experience, it's not worth the argument because you won't save a lot of gas either way. So just do what's comfortable.
Method: We drove the full 55 mile-loop in two cars at equal speeds both times — 65 mph. The first loop we drove with the A/C on and the windows up. The second loop we drove with the A/C off and windows down. In the second test we drove 20-mile loops. This was far enough to see our gas mileage level off and remain steady on the computer trip meter.
The Mythbusters also address this question in episodes 22 & 38. 22 found the AC on, windows up scenario to be more efficient. But when they revisited this question they found a flaw in the original results. The final outcome, as reported in episode 38, was that AC on & windows up was more efficient above 50 mph, but ac off, windows down was more efficient below 50 mph.
My own, personal, test show no measurable difference (tested on several vehicles from a 300 hp V8 Lincoln Navigator to my current FIT) and AC on is much more comfortable.
The only car that I have ever owned that suffered from power loss when the AC was on, was a 1972 Chevy Vega, and it was a serious piece of crap.
Last edited by TheSaint; 10-22-2008 at 11:41 AM.
#20
10-22-2008, 03:20 PM
I'm not sure if i have it working properly, still!
If i have the following settings:
- fan 2
- vent to defrost
- A/C off position (de-pressed), light is off
is the AC actually off? With fan 1, i can hear the compressor kick in but no AC light. I forgot what was the behavior before the hack. Would the light be on even though the button is left de-pressed?
Thanks