And even economists.

This may be better suited for a different forum, but I know you guys are in to this stuff:
How is the AFR affected by ambient temp variations? I know colder air makes more power, but what is the effect of colder temps on MPG? (assuming that you can keep your right foot from enjoying the increase in HP).

 

Cold weather can reduce fuel economy, since your engine doesn't operate efficiently until it is warmed up. In colder weather, it takes longer for your engine to warm up.

 

Cold air just means more oxygen. More oxygen means more fuel.
All else equal, you shouldn't get better or worse mileage due to air temp. Then again, if you let the engine warm up longer in the cold, or use the AC when it's warm...

 

Let's assume, for the sake of argument, that warm up is not an issue.
Equal cars, at op temp, driving in 25F vs 50F, all other factors equal. Which gets better fuel economy?

 

The one with the elephant in the trunk gets worse

 

I don't think it increases fuel consumption. The only way to tell would be whether the air temp sensor effects the amount of fuel entering the engine. I think the cold air just lowers the temp of the fuel mixture. This should require more energy to ignite it, while also producing more energy from the explosion. It seems to me that this shouldn't effect the mixture, it would just make for a more powerful explosion of the mixture.

 

EQUAL cars, furry one.

 

Also consider the density of the cold air you're plowing your car through. Colder air means that at a given speed you are bumping more air molecules out of the way as you move along. If you fly, think higher indicated airspeed to fly the same true airspeed on a colder day. I vote for very slightly reduced mileage on a cold day.

 

Equal cars get equal MPG

Factor in speed as well, deser air means more drag. What about altitude? Wieght? Mods? Barometric Pressure? Humidity? Summer or Winter wheels/tires? are you running defrost? Widnows down in heat and up in cold?

FYI my Physics prof hated me as I often looked at all factors and even got him to say "ignoring the laws of science" just to get me to look at the question. Temp alone with out ECU should have little to no effect on milage, in theory; but I think this is cause for some lab testing with Bim-COm (Yes I still want it!!!).

 

That is true. However, it also depends, then, upon the color of the car as its well known that different colors go faster (dont laugh).

For example, to get some odd ball colors like some metallics, the paint has to be heavier to account for the metallics in the paint and possibly more layers.

Thats why CR/W is always the fastest.

 

At least as it stands now in the US, in colder air/climates, one gets more fuel for their money...

 

If the air/fuel mixture is effected by the air temp sensor, then it will put more fuel in with the air to keep the mixture from being too lean. If you take advantage of the extra power...you will use more fuel. This in addition to the denser air you are driving through...definitely more fuel consumption. It might only 1 mpg though. It's worth the added power though.

 

Colder temps DO reduce gas mileage. We also own a Honda Insight and this topic is very big over on their forums. Colder air means denser air, which means more fuel molecules are needed to keep a stoichiometric A/F ratio. It's just like running a reduction pulley...more air needs more fuel to keep stoich.

If you run the same car in 25 degree air and 80 degree air, the one in 80 degree air will get better mileage. This, of course, means you can't run the A/C when it's 80. The A/C eats more mileage than the colder air.

 

not that it really really matters for the point of this thread. But MINIs do not run at a stoichimetic A/F. Most cars with cats don't... it would burn them out in a hurry. Insights and piruses may be equiped with special cats that can run at the higher EGTs. or they may not and they may not run at stocihiometric a/fs.

also, the difference between cold weather mileage and warm weather is negligable. Too many other factors involved to get an exact answer. the best thing to do would be to have a climate controled engine dyno... that would be the only true way to find out if the engine used more fuel. whether or not cold weather has a huged effect on drag on a car going 50mph is a completely differnt story.

 

I know but the computer is still trying to keep a set A/F ratio, even if it isn't stoich. The gas mileage difference might be negligible in an MINI but it's very noticeable in an Insight. As the temp drops near freezing, gas mileage really takes a hit.