Does turning the A/C Auto on consume more fuel?

sunnywuh · 05-07-2006, 09:37 PM

Hi guys,

do you think that turning the A/C AUTO on necessarily consume more fuel? I notice under the same temperature AUTO function carries a higher fan speed and also it makes most of the cool air coming out from the top of the dashboard.

Do you know the location of the solar senors? Do they work in sync w/ AUTO function and vice versa?

Pazzuzzu · 05-07-2006, 09:48 PM

Actually the A/C uses a comprerssor which adds a load onto the engine and electrical, it can consume 6-10 hp (approx). Yes it makes your mpg worse but no worse than opening your windows (full) while highway driving. Check out your mpg on the gauge and see it drop when you pull down your windows and or turn on A/C.

ADHD · 05-07-2006, 09:56 PM

well i did some experimenting on this today driving 400miles breaking in my car. and I noticed that keeping the A/c set at AUTO with the fan on 2or3..
setting driver side at 73 and the passenger at 77
periodically pushing the flake for a/c when it got a bit warm and Id turn it off after about 10min or so and I wouldnt have to push the flake for another half hour or so.
NOt once did i ever push the Max button and my MPG on the onboard computer is 24.5 I noticed the majority of the time though the little needle sits over 30mpg the whole trip. I just got back and need to sleep but in the morning ill figure out its exact MPG i recieved by calculating gas/miles.
Im not sure if this is the most efficient way but it did really Great for me today!

willpooted · 05-07-2006, 09:59 PM

AC is something you need (at least I do). If you want to save gas, try not to be rough with the gas and brake pedals.

sunnywuh · 05-07-2006, 10:01 PM

sorry i didn't make myself clear enough, i am trying to compare the mpg between A/C AUTO and A/C with manually setting the fan speed. Becoz i'm under the impression that A/C Auto does consume a bit more fuel.

espo · 05-07-2006, 10:37 PM

Depends on the end temperature that you have in the cabin. If you keep the A/C on Auto with a higher temperature then you would have in the cabin with the fan on manual, then the Auto feature would use less gas in the long run. In the short run, the AUTO feature will load up the system faster to drop the temperature to the setpoint.

I would also venture a guess that the auto feature will vary the load on the compressor to keep the set temperature rather than a constant load when you have it in manual. So you would save some gas there also.

sunnywuh · 05-07-2006, 10:49 PM

hm..that makes sense. I never see the fan speed drop on AUTO - the weather condition in HK during summer time is averaged at about 30C which is around 86F, i usually set the cabin temperature at 23C(74F).

How about the solar sensors? Theortically speaking, they only work while the AUTO is on, right?

ska///235i · 05-07-2006, 11:17 PM

wow..u guys set to 74F ?
I freakin need AC when its 74F outside, I like my Temp to be around 60-63

ADHD · 05-07-2006, 11:29 PM

Quote:

Originally Posted by ska

wow..u guys set to 74F ?
I freakin need AC when its 74F outside, I like my Temp to be around 60-63

u wear a long sleeve suit I imagine! Otherwise Id be freezing!

05-07-2006, 09:37 PM	#1
sunnywuh Lieutenant 19 Rep 508 Posts Drives: E90 330 Join Date: Nov 2005 Location: Hong Kong iTrader: (0)	Does turning the A/C Auto on consume more fuel? Hi guys, do you think that turning the A/C AUTO on necessarily consume more fuel? I notice under the same temperature AUTO function carries a higher fan speed and also it makes most of the cool air coming out from the top of the dashboard. Do you know the location of the solar senors? Do they work in sync w/ AUTO function and vice versa?
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05-07-2006, 09:48 PM	#2
Pazzuzzu Private First Class 8 Rep 130 Posts Drives: 330i SP Arctic Metallic Join Date: Feb 2006 Location: Montreal Canada iTrader: (0)	Actually the A/C uses a comprerssor which adds a load onto the engine and electrical, it can consume 6-10 hp (approx). Yes it makes your mpg worse but no worse than opening your windows (full) while highway driving. Check out your mpg on the gauge and see it drop when you pull down your windows and or turn on A/C.
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05-07-2006, 09:56 PM	#3
ADHD Brigadier General 197 Rep 4,095 Posts Drives: F30 328i Join Date: Apr 2006 Location: Magic Mountain iTrader: (38) Garage List 21 M540i [0.00] 07 e90 335 [0.00]	well i did some experimenting on this today driving 400miles breaking in my car. and I noticed that keeping the A/c set at AUTO with the fan on 2or3.. setting driver side at 73 and the passenger at 77 periodically pushing the flake for a/c when it got a bit warm and Id turn it off after about 10min or so and I wouldnt have to push the flake for another half hour or so. NOt once did i ever push the Max button and my MPG on the onboard computer is 24.5 I noticed the majority of the time though the little needle sits over 30mpg the whole trip. I just got back and need to sleep but in the morning ill figure out its exact MPG i recieved by calculating gas/miles. Im not sure if this is the most efficient way but it did really Great for me today!
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05-07-2006, 09:59 PM	#4
willpooted Private 2 Rep 83 Posts Drives: 2006 325i Join Date: Jul 2005 Location: Encino, CA iTrader: (0)	AC is something you need (at least I do). If you want to save gas, try not to be rough with the gas and brake pedals. __________________ 5/06/05 \| 2006 Alpine White 325i \| Premium \| Sport \| Xenon \| Beige Dakota w/ Poplar
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05-07-2006, 10:01 PM	#5
sunnywuh Lieutenant 19 Rep 508 Posts Drives: E90 330 Join Date: Nov 2005 Location: Hong Kong iTrader: (0)	sorry i didn't make myself clear enough, i am trying to compare the mpg between A/C AUTO and A/C with manually setting the fan speed. Becoz i'm under the impression that A/C Auto does consume a bit more fuel.
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05-07-2006, 10:37 PM	#6
espo Captain 12 Rep 715 Posts Drives: 2014 M235i Join Date: Sep 2005 Location: Sugar Land TX iTrader: (0)	Depends on the end temperature that you have in the cabin. If you keep the A/C on Auto with a higher temperature then you would have in the cabin with the fan on manual, then the Auto feature would use less gas in the long run. In the short run, the AUTO feature will load up the system faster to drop the temperature to the setpoint. I would also venture a guess that the auto feature will vary the load on the compressor to keep the set temperature rather than a constant load when you have it in manual. So you would save some gas there also. __________________ E46 325xi Oxford Green/Sand Leatherette/Myrtle Wood Auto ZCW - Retired E90 330xi Mystic Blue/Black Leather/Aluminum 6sp Manual ZSP/ZPP/ZCW/CA - Retired F22 M235i Mineral Gray/Red Leather/Aluminum 6sp Manual ZPP/ZTP
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05-07-2006, 10:49 PM	#7
sunnywuh Lieutenant 19 Rep 508 Posts Drives: E90 330 Join Date: Nov 2005 Location: Hong Kong iTrader: (0)	hm..that makes sense. I never see the fan speed drop on AUTO - the weather condition in HK during summer time is averaged at about 30C which is around 86F, i usually set the cabin temperature at 23C(74F). How about the solar sensors? Theortically speaking, they only work while the AUTO is on, right?
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05-07-2006, 11:17 PM	#8
ska///235i ***** noob 1370 Rep 10,479 Posts Drives: 325xi>M235i>428GCx Mspor Join Date: Sep 2005 Location: Boston iTrader: (34) Garage List 2006 325xi [0.00]	wow..u guys set to 74F ? I freakin need AC when its 74F outside, I like my Temp to be around 60-63 __________________ 2006 325xi (Sold) 2014 M235I (Current) 2015 428xi Gran Coupe (STB)
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