How does Climate Control affect MPG?

Jez · 2 Dec 2009 at 10:27

izzy eckerslike said:
I've never understood that part about the alternator affecting the engine efficiency with extra load as it's constantly belt driven anyway

Thats not how it works, as load increases so does the proportionate resistance to its movement and therefore its load on the engine. An example of this is the fuel consumption increase when turning on heavy electrical systems such as heated seats.

Firestar_3x said:
My understanding is a larger electrical load on the alternator means a bigger force trying to stop the alternator from spinning, so the engine is required to put more physical power into the alternator to stop it from stalling under the electrical load demand.

But i'm happy to be corrected if this is wrong.

:thumbsup:

Street · 2 Dec 2009 at 10:27

I've never really noticed the climate control affecting my mpg much.. Maybe 1 or 2mpg at the most! I just tend to leave it on now..

beermonster · 2 Dec 2009 at 10:28

izzy eckerslike said:
I've never understood that part about the alternator affecting the engine efficiency with extra load as it's constantly belt driven anyway

It is constantly belt driven but under load it will be harder to turn, the alternator thus require slightly more engine power to drive it, this is why your belt will squeal if its abit slack when you put high current things on such as the heated screen.

BigglesPiP · 2 Dec 2009 at 10:30

Firestar_3x said:
Turning the indicator on probably makes a mpg difference to that pile of junk.

It was noticeably less slow uphill with the air-con off, it was like a boost button. Classic hire car.

Lashout_UK · 2 Dec 2009 at 11:38

Difference is pratically non-existent on large displacement engines as it's not like they're working hard in the first place - but little four pots and so on can suffer a decrease in mpg with that extra load.

gurusan · 2 Dec 2009 at 11:40

Lashout_UK said:
Difference is pratically non-existent on large displacement engines as it's not like they're working hard in the first place - but little four pots and so on can suffer a decrease in mpg with that extra load.

Don't think so....the difference might even be less in a smaller engine as they are more efficient.

Peerzy · 2 Dec 2009 at 11:42

Girlfriends Mum refuses to use AC on her 57 plate VW Polo 1.2 S because it slows it down too much that it's 'unsafe' :rolleyes:

My climate control is always on.

Duke · 2 Dec 2009 at 11:54

Jez said:
I think we all know what eco mode on climate control does

I didn't, learn something new everyday

Jez · 2 Dec 2009 at 11:54

What did you think it did?

Duke · 2 Dec 2009 at 12:05

Never knew CC had Eco Mode. Not had CC car

div0 · 2 Dec 2009 at 12:05

Jez said:
What did you think it did?

Gives you a warm fuzzy feeling knowing you're doing your bit for the planet?!

Jez · 2 Dec 2009 at 12:09

Duke said:
Never knew CC had Eco Mode. Not had CC car

Ah, right. They always have an option to ignore the use of the compressor IME.

BMW (and i assume some others) bizarrely have it the other way round where you have to actually turn the compressor ON marked with a light, as if you wouldnt want it to be the default option

But the option is always there and amounts to the same thing whichever way round it is worked.

OllyM · 2 Dec 2009 at 12:56

Duke said:
Never knew CC had Eco Mode. Not had CC car

I thought your 323i had climate control?

mrk · 2 Dec 2009 at 13:04

Eco mode isn't quite comfortable enough though and still mists the windscreen on wet, cold mornings/nights!

I like cold air from top vents aimed up and hot air from the floor vents - nice.

The AC button will remained engaged forever more!

[TW]Fox · 2 Dec 2009 at 13:05

mrk said:
Eco mode isn't quite comfortable enough though and still mists the windscreen on wet, cold mornings/nights!

Well of course, because the AC doesn't operate :confused:

Huge levels of facepalm in this thread.

mrk · 2 Dec 2009 at 13:08

Which is my point...why have eco mode when it does the same thing as the temp set xx anyway since it's not going to get colder than that either way - going by the eco mode button comments above anyway.

Westyfield2 · 2 Dec 2009 at 13:09

In dad's 5: Absolutely no affect on MPG.

In my VTR: I dream of it having aircon

[TW]Fox · 2 Dec 2009 at 13:10

mrk said:
Which is my point...why have eco mode when it does the same thing as the temp set xx anyway since it's not going to get colder than that either way - going by the eco mode button comments above anyway.

You don't have an eco mode on your car. You have a ********* button instead which either engages or disengages the AC.

Some cars have an eco button instead - the function is the same, it just TURNS OFF THE AIR CONDITIONING! Thats all it does.

Eco = NO AIRCON = ********* button = turning the aircon off.

Get it?

Jez · 2 Dec 2009 at 13:12

mrk said:
Which is my point...why have eco mode when it does the same thing as the temp set xx anyway since it's not going to get colder than that either way - going by the eco mode button comments above anyway.

The eco mode simply prevents the system using the compressor, which i dont see why you would ever want to do for the reasons of discomfort as you have mentioned. It just works in the opposite way to the BMW "AC" button on climate equipped vehicles.

[TW]Fox · 2 Dec 2009 at 13:14

Eco button is simply an AC off button. Thats it!