IIRC from chemistry, don't reactions speed up in the presence of heat...due to increased molecular motion? Remove heat = slower reaction, add heat = faster reaction?

Not trying to be argumentative...interesting topic

 

Sometimes. But for a reaction to expell the most energy, it has to go from a high energy level to a low energy level. A cold day is the most efficient as far as the energy exchange goes. But cold weather takes its toll on other parts of the drive train. Not to mention the added drag from the "denser" air.

 

The computer monitors how much air is entering the intake. When the air is colder, the air is denser, so the computer reads it as "more" air. So to keep the air/fuel mixture at a certain ratio, the computer adds fuel to keep from reaching a lean condition.

 

amen... lol end of discussion.

 

Not necessairly. When the air is cooler, it takes less of it to make the same a/f ratio possible. So the computer adds the "correct" ammount of fuel for a given quantity of air as corrected by the IAT, MAF, BARO etc. The ammount of fuel is dependant on air mass, not TB setting. The TB is just a mechanical means of regulating air flow....

So in effect... On a cold day, you won't have to press the "gas pedal" as far as you would on a hot day, because the air is more dense, and you get more O2 per cubic foot of air.

At least, that's how I see it.

If your scenario was true, then the truck would accelerate. Cause more air = more fuel = more power.

 

I would say mpg's improve in the summer, whatever the reason. Having the A/C on in the city hurts mpg's, but on the freeway helps, less drag they say. I leave the windows closed as much as possible when travelling 60+ mph, vent or a/c on depending on outside temps.

 

Actually, the fuel in North Texas completely changes in the summer due to emission issues. I don't know that it has an impact on mileage, though. It's called RVP gas. Low RVP gasoline is fuel that is refined to have a lower evaporation rate and lower volatility than conventional gasoline. It also reduces the evaporative emissions generated during vehicle refueling and therefore decreases the emissions of volatile organic compounds (VOCs) and other ozone-forming emissions.

Currently, the Regional Low RVP Gasoline program requires that low RVP gasoline be used in 95 central and eastern Texas counties during the summer months when ozone pollution is at its worst.

My two pennies...

 

No problem. As I recall, endothermic (needs heat) react better with more, exo (makes heat) works better with a higher differential, ie colder ambient.

I agree, interesting idea. I hadn't considered the effect of viscousity of transmission oil etc, that might slow things down, also, if colder air is more dense (makes sense) then there would be more wind resistance....?