Yay for air con... boo for fuel economy! \o/

Firestar_3x said:
In real terms AC basically makes 0 difference to fuel economy.
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Depends what your real terms is. Short journeys will have a decent effect whilst you chill off the interior.

The longer the journey the less the AC is actually used, AC does use a lot of fuel. Keeping the interior of a car around 18C doesnt use a great deal though compared to circulating ambient air. Its not zero though :p

This is where climate is useful rather than pure AC as its chasing a temp not just providing cold air, although AC will moniter the evaporator temperature anyway. To summarise the duty cycle of what is around 1.5-2.5KW engine load is pretty low. Otherwise you would always be giving 3-4bhp to the compressor.
 
Ah, myth busters, that was it:-

Last time around, in "AC vs. Windows Down", the MythBusters concluded that using AC was more efficient than opening your windows to cool down with a caveat. They found that over 50 mph, you're better off your AC on, but slower than that, open your windows.
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I'll make the concession - AC use for short, low speed journeys does harm MPG by a reasonable margin.

I'm basing most of my statements on a reasonably long journey to work, at reasonable speeds (NSL/Motorway) and CC in use.
 
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amigafan2003 said:
I find it amusing the amount of people that drive around sweating with the windows down in cars that quite clearly have some form of aircon (MKIII Mondeos for example).
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Sometimes it's just nice to drive with the windows open. Ive just driven back home through a rural area with windows down and some good music on the stereo, despite having perfectly good air-con. I just enjoy driving with the window down and my arm on the door in this weather; in fact, there's not a lot that's better on a sunny day in my opinion :)
 
Yeah, I agree, I prefer the Westfield with the air con off and the windows down ;-)

Oh wait, it doesn't have air con. Or windows. Or a windscreen!
 
Does anyone know when the refridgerant changed from R12 to R134a? I am struggling to find it as I need to know what my car has in it.
 
Does anyone know when the refridgerant changed from R12 to R134a?
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It's irrelevant as you can't get R12 now as it's banned (CFC's etc). You can put R134 in it but the seals wont last as long and it wont be as cold. You could use R49 but it's hard to find but will make your seals last a bit longer and it's ok to use with mineral oil unlike R134.

But just for the hell of it the change over was 1994 with R12 being banned for refills in 2001.
 
Can find places that do RS24 too, there are also some other 'drop in- R12 replacements that you can get. Need to look into it more. The annoying thing is my car was built in 1994. :(
 
My air-cons Receiver Drier disintigrated last year (2 hours after having it checked and regassed :(), I bought a new one last year, and it's still waiting for me to fit it :eek:

No doubt by the time I get round to doing it I wont need it :p
 
saitrix said:
Can find places that do RS24 too, there are also some other 'drop in- R12 replacements that you can get. Need to look into it more. The annoying thing is my car was built in 1994. :(
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I've just seen a mobile air-con place quote 120 quid for a R12 to R134 conversion
 
Overlag said:
lol weedy engine. So mr eddie stobart (R122 something?) is lying when he said it makes a 0.5mpg diff on his lorry, which only averages 8 anyway.... 0.5mpg is rather big if your as low as 8. Is that a weedy engine? No.

AC causes massive engine drag which you have to overcome with more throttle. The fact that all cars(1.2l, 2l, 2.5t, 3l v6 etc) ive been in jump 250-500rpm when the AC is turned on proves this.

Im willing to BET it does effect your Scorpio as well.
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My mondeo doesnt jump/stutter in the slightest when the air con is engages. Just a quiet click from under the bonnet.

Makes about 1mpg difference (out of 45), but having the windows down has a bigger impact
 
Overlag said:
lol weedy engine. So mr eddie stobart (R122 something?) is lying when he said it makes a 0.5mpg diff on his lorry, which only averages 8 anyway.... 0.5mpg is rather big if your as low as 8. Is that a weedy engine? No.

AC causes massive engine drag which you have to overcome with more throttle. The fact that all cars(1.2l, 2l, 2.5t, 3l v6 etc) ive been in jump 250-500rpm when the AC is turned on proves this.

Im willing to BET it does effect your Scorpio as well.
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That doesn't sound right. In my understanding aircon will use a certain amount of power - say 2kw. If you have a 200kw (268bhp) engine it'll make a small percentage difference, if you have a 50kw (67bph) engine it'll make a bigger percentage difference.
 
Overlag said:
lol weedy engine. So mr eddie stobart (R122 something?) is lying when he said it makes a 0.5mpg diff on his lorry, which only averages 8 anyway.... 0.5mpg is rather big if your as low as 8. Is that a weedy engine? No.

AC causes massive engine drag which you have to overcome with more throttle. The fact that all cars(1.2l, 2l, 2.5t, 3l v6 etc) ive been in jump 250-500rpm when the AC is turned on proves this.

Im willing to BET it does effect your Scorpio as well.
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It makes no noticeable difference on a proper car with climate control and not just "AC". I do not notice a single 0.1 difference between "eco" and normal. The compressor has a clutch and is driven only when necessary, which with our weather and with decent double glazing to keep the car insulated is only for a while i would guess while it initially cools the car down. As i say, over a tank, nada.
 
clv101 said:
That doesn't sound right. In my understanding aircon will use a certain amount of power - say 2kw. If you have a 200kw (268bhp) engine it'll make a small percentage difference, if you have a 50kw (67bph) engine it'll make a bigger percentage difference.
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Both engines would be using a similar amount of power under cruise conditions though, not there peak figures at rpms that would need 2nd gear on the motorway.

Bigger engine of course needs less extra throttle to counter the effect which is why you notice it less along with the extra mass of it.
 
But that's not on all cars though is it? For example BMW cars have a variable AC compressor so the power used is not a constant figure?
 
There are clearly going to be differences in every car.

My Focus had a notable power drop with the AC on. Very noticeable.
The S2000 has code in the ECU to apply an idle throttle increase with the AC on to compensate for the extra load.

I only use AC when I feel I need it, I never leave it on. If it does not affect economy it certainly affects total power available at my right foot :p
 
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