07-01-2013, 02:27 PM | #1 |
Gas Performance of AC vs Drag
I brought up in one of the gas mpg threads "Does running the AC affect my mpg?" and I decided to do some research. Of course the answer is yes, but what about windows down vs AC?
In today's world, the average (modern) car is fairly aerodynamic and getting better at gas usage. When it comes to deciding to roll the windows down or run the AC, it seems physics solves the issue (sort of). The general rule I found was that 52mph is the average speed where having the windows down will lower gas efficiency due to drag. Anything under 52mph with windows down allowed the car to utilize the gas more efficiently. Now that was a GENERAL AVERAGE amongst standard cars. I know that our cars are probably more aerodynamic than most, but has anyone really had firsthand experience with this in the community? I haven't had the luxury of a LONG ride yet, but I would love to see REAL LIFE inputs on performance difference. Other interesting questions: How does a convertible affect the aerodynamics of the car/gas efficiency (down and up)? How does the convertible 2nd set of back windows (top up) affect the aerodynamics of the car/gas efficiency? TLDR: Ride with your windows up and AC off and your car will be at max performance
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07-01-2013, 02:42 PM | #2 |
The gritos pollo!!!
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interesting. seems at 70+ i get a lot of air turbulence in side the car with them down. now you have me wondering.
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07-01-2013, 02:56 PM | #3 |
you will definately get better gas mileage with windows up and AC on over having windows down.
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07-01-2013, 03:57 PM | #4 |
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Just drove mine from delaware to florida. 1600 miles on it to start, 2500 now. 1ls, ran as high as 30.1 ac off some traffic caused me to end with 29. When it got to hot went to ac and ran 28-28.5mpg. Range of speed was 60-77 ran 5 to 7 mph over speed limit all the way.
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07-01-2013, 04:12 PM | #5 | |
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07-01-2013, 04:20 PM | #6 |
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Myth busters did an episode on this. I'm sure it's on the YouTube somewhere.
And windows down will increase the drag coefficient as air is being sucked into the cabin. |
07-01-2013, 04:23 PM | #7 |
Drives: 2011 Camaro Synergy II Join Date: May 2013
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This will be interesting...
Our cars are narrower across the rear of the window opening, than across the front. That would lead me to believe that the windows down would not make much of a difference than up. On the Camaro anyway. Hmm... Lee |
07-01-2013, 04:30 PM | #8 |
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Ummm... Isn't this just common knowledge?
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07-01-2013, 04:44 PM | #9 |
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I thought modern AC and ventilation systems work in such a way that the compressor cycles on and off whether we are using AC or not. Even in the winter while we use the heat. Don't they cycle on/ off year around to keep them lubricated?
In which case, the drag on the engine would be the same either way.
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07-01-2013, 05:18 PM | #10 | |
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yes, but that was only at speeds over 50. the first time they did it they kept the speed low, like 25 or something, so the tires wouldn't wear as bad. and that result showed no change in MPG. the second time they did it (because a lot of people wrote in making note of the speed) they ratcheted the speed up and it did in fact show a decrease in MPG with the windows down. |
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07-01-2013, 05:54 PM | #11 |
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Back in the day when AC compressors were piston type you could really tell the difference in drag and mileage. Turn one of those baby's on and the car slowed down. With the new style rotary AC compressors they have much less drag. No mater how much it costs, I am keeping my AC on while I drive the car. I want to be comfortable. There's more to life than gas mileage.
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07-01-2013, 06:02 PM | #12 |
The gritos pollo!!!
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almost fell over when i saw the stig has "fireproof moderator"
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07-02-2013, 07:40 AM | #13 |
So I guess the only people who have knowledge/information about the aerodynamics of the car is GM. I guess we just have to trust that they are thinking of windows down drag.
I am still curious how much drag a convertible produces with the top up and down.
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07-02-2013, 08:45 AM | #14 | |
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