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02-16-2009, 05:20 AM | #1 |
A different Air Con and FE question
Ok, Who can answer this?
If i'm driving my car with the air con on and the fan on 4 does that use more fuel than if i have the air con on and the fan on 3, 2 or 1?
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02-16-2009, 09:43 AM | #2 |
Steals terrorist's lunch
Drives: 2007 Yaris Liftback Join Date: Mar 2007
Location: Reno, Nevada, USA
Posts: 1,299
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There is an unknown balance point between taking longer to move enough air to cool the car off (which uses more fuel as the a/c is on longer) vs. using more electricity to turn the blower faster (which uses more fuel as the alternator clutches due to the load, placing more of a load on the engine). The a/c compressor is by far the larger drain but the fan isn't free, either.
It is generally accepted that running at full cool with the fan on 3 or 4 (I find 4 to be too loud) until the desired temperature is reached is best, then either "pulsing" it on the downhills, or just as needed, rather than letting it remain on full time.
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02-16-2009, 10:44 AM | #3 |
Drives: Black Vitz Liftback Join Date: Dec 2008
Location: Salt Lake City
Posts: 238
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technically the answer is yes, this question has been addressed on a "car talk" radio show. Increased load on your alternator, a/c compressor may engage more often to cool the condensor, but the car talk guys said the amount of fuel used even over a long period of time was so small it was meaningless, you'd save more turning your car off at drive throughs if there longer than 30 seconds. Just know running your fan on high a lot will probably shorten the life of a very expensive blower replacement more than save some gas.
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02-16-2009, 12:15 PM | #4 |
Drives: 2013 Chevy Spark 1LT 5-speed Join Date: Oct 2008
Location: Oklahoma
Posts: 1,185
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If you had automatic climate control I'd say it'd make a difference. If not, I doubt if reducing the resistance on the blower motor will cause you to use more fuel.
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02-16-2009, 12:48 PM | #5 |
Whew Who..
Drives: 2 Yaris Hatchs and Tacoma Join Date: May 2006
Location: So. Ca.
Posts: 78
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I agree with 1stToyota
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02-16-2009, 12:57 PM | #6 |
Drives: 2013 Chevy Spark 1LT 5-speed Join Date: Oct 2008
Location: Oklahoma
Posts: 1,185
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Yeah, since we don't have any temp sensors in the cabin I don't see how blower motor speeds could ever play a role in clutch cycle time. More likely our temp blend door setting would make more of a difference, with maybe a temp probe or expansion valve on the evaporater core that would be tied in with the clutch cycles...
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02-22-2009, 02:07 PM | #7 | |
Quote:
It comes down to initial design. You should be able to utilize everything in the vehicle, such as headlights, 12V sockets with the AC on and fan turned on high with the brake pedal pressed (turns on brake lights). Vehicles are built to run all their required electrical loads without worry of stalling or having to put the transmission in neutral and give it fuel in order to sustain itself from stalling. The PCM can adjust fuel to compensate for above average loads and help boost the idle speed slightly to compensate. Sorry if I don't listen to or believe in CarTalk radio shows. FYI: Don't forget that when you have the knob set to ANY defrost position the A/C compressor will run. This is especially important not to shut the vehicle off or turn it on when the selector knob is on a defrost setting. Turning it to vent or floor is the way to go, not to save fuel, but to save wear and tear on the system. The compressor is one of the largest electrical load devices in the vehicle. Keeping it off will aid in starting and overall wear and tear. |
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02-22-2009, 06:33 PM | #8 | |
Quote:
Thanks
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02-22-2009, 08:54 PM | #9 |
I have to disagree with you; the fan, the compressor clutch, almost everything running on electricity get "disconnected" when the starter is engaged. So you're not lessening the load on the starter by turning things off. But i agree the more you use something, the more it wears
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02-22-2009, 11:11 PM | #10 | |
Drives: 2008 Yaris Sedan Join Date: Oct 2008
Location: Earth
Posts: 13
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Quote:
I know on a hot day, fan on high cools the car faster, but lower the fan speed after a few minutes, and it will cool even faster. |
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