Mythbusters AC dilemma

Using 2 identical SUVs was the problem. Even though they may be the exact same spec, chances are one is a bit more effiecient. It would off been a more objective test, if they had done the test several times using just the one SUV, or doing the test twice and swapping the SUVs.

Personally, if it's hot. I'd rather use the aircon, be comfortable, not get deafened by wind noise, and loose a couple mpg.

I'd agree with that, A/C would put more load on a smaller engine, as would disrupting the airflow.

New Fiat Panda - 56mph down the motorway, for 35 miles each way...

AC off, Windows Up - 58.2mpg AC on, Windows up - 54.9mpg AC off, windows down - 53.7mpg AC on, windows down - 49.4mpg

Official MPG of the car is 61.2mpg

Malc wrote on Sun, 27 Mar 2005

20:34:31 GMT:

Yeah, I watched it too...

What speed were they going for that test, though?

I was thinking that if they'd done the computer test at a higher speed, they could well have got different answers for the two tests.

Low speed, low drag from windows, so windows are better than the AC

High speed, lots of drag, AC better than windows.

Using SUV's was probably not a good test anyway, as the percentage of consumption difference would be very small.

The data on a smaller car, with much better economy, would give a better indication of the differences.

The message from "Malc" contains these words:

By chance my brother mentioned over the weekend that his Turan "instant consumtion" meter shows a slight increase in mpg if he opens the windows at 60mph, regardless of AC.

The message from "Malc" contains these words:

Call that good? I don't! I know our gallons are a tad bigger than theirs but if that's what their vehicles do I'm not surprised the rest of the world doesn't appreciate 'em.

You're me, you are. A US gallon is more or less exactly 5/6 of its Imperial cousin. 13mpg is staggeringly bad, unless they were doing a ton.

Indeed - at idle, the A/C can IIRC almost double your fuel consumption in some cars. So in traffic windows are more economical than AC, even if they are pointless. So yet again, you can't win. Just use the AC.

Guy King ( snipped-for-privacy@zetnet.co.uk) gurgled happily, sounding much like they were saying :

Ours - 4.5l, theirs - 3.8l

You and me both

They were going to fill both tanks and run at 70 or 80 until they stopped which would have been about 7 hours. The racing track owners stopped that on safety grounds.

I was quite staggered when I heard the mpg. It's quite a fun programme if you get Discovery though, the destruction of a boom lifter was good.

Hmm, can't think of any races that last that long

Depends on vehicle speed and design. At low speeds the open windows will have little effect on economy (though also little benefit for cooling), whereas the A/C compressor would still be drawing power from the engine. As vehicle speed rises it will reach a point where the extra drag imposed by opening one or more windows or sunroof(s) are more than the load of the A/C compressor and condenser fan(s)...

Darren

In news:rNE1e.6655$ snipped-for-privacy@text.news.blueyonder.co.uk, Malc decided to enlighten our sheltered souls with a rant as follows

I drive a very large SUV [1] for a living, and having the windows open

*definately* increases fuel consumption. I've also done the same experiment using factory fuel computers and they seem to agree with my findings.

The only time I've found AC to cause a slight increase in fuel consumption is sitting stationary in traffic. As it is, I'd much rather sit in traffic in a quiet, cool, dehumidified atmosphere listening to the radio than to sit there, listening to other vehicles and breathing in nasty 'orrible diesel fumes.

AC is brilliant.

The message from "Pete M" contains these words:

Aroooogah, Arooogah - undefined footlingnote alert.

A little known fact with modern AC systems is that especially the newer electrical ones are amazingly efficient. Most older type compressors, such as fitted to Volvo 960, V70, V90 etc... Switch off under hard acceleration to give you a little more power.

Andy

24Hour LeMans!!!!

Andy