Stupid A/C question... (any MPG effect of max. vs low setting?)

[trooper Tdiesel]

Originally Posted by SentraSE-R

If you have a luxury car, you're hosed, because it will run the AC all the time (within its duty cycle), mixing heat with the cold air in the Summer to regulate temperature, and running the AC to dehumidify the heater air during the Winter.

yes high end cars will default to A\C on.

but ive yet to find one that has no loop hole back door,
set it to feet and turn the A\C butten off. but the moment you turn it back to defrost or turn the engine off/on the A\C resets to being on.



in short, any auto base model or high end, with working A\C set to defrost has it running, weather the A\C butten is pushed or not

thus why if you have it on the floor mode with A\C butten off and it starts raining. you flip it to defrost and it automatically turns the A\C on to deumidafy the window. weather you want it too or not this is happening
well ok ive yet to find one, so there may be one out there that does not. but im gessin theres very few of them, if any.

also the only difference in normal to MAX A\C mode is that normal mode is fresh air
and MAX mode is reticulate mode

MAX is not in any way a higher out put, other then cooling the same air in the cab.

[graydonengineering]

My engine is so gutless that I can "feel" the load of the AC if it is on and from what I can tell it loads the engine just about as much no matter what setting I have it on. Turing it off while accelerating is like a mini-nitor boost! As a result, I cycle it on only going down hill or decelerating since I have a little energy to spare then. It blows cold for a good 20 seconds after I shut it off.

Also you should never come to a stop (arrive at your destination) with the AC switched on for two reason:
1. It's a waste of energy since it will blow cold for a while after you switch it off and number 2, even important to non-ecomodders, the wet cooling system will take much time time dry this way and smell of dank mildew over time... even in new cars but especially in older cars with some dust inside the vents. Do yourself a favor and switch it off (but leave the fan running) about 60 seconds before you park.

On a side note, it never occurred to me to run re-circulate in hot weather! lol. I used it all the time in the cold in Oregon but I an new to driving in the heat. Thanks all for the tip!

[pletby]

Originally Posted by graydonengineering

My engine is so gutless that I can "feel" the load of the AC if it is on and from what I can tell it loads the engine just about as much no matter what setting I have it on. Turing it off while accelerating is like a mini-nitor boost! As a result, I cycle it on only going down hill or decelerating since I have a little energy to spare then. It blows cold for a good 20 seconds after I shut it off.

Do I ever know what you mean. When I turn on my A/C it feels like I just threw an anchor behind me. I can't wait to get my UG and see the difference in fuel economy when I turn that A/C on.

[wickydude]

There are also cars that use an adjustable swash plate compressor. Basically it changes the volume of coolant being pumped, depending on the required pressure in the system.
That means it will draw less energy on low cooling demand than on high demand.
Don't know about yours, maybe you could ask Toyota.
This shows roughly how it works
One-Way Swash Plate Internally-Controlled Type | Compressors - TOYOTA INDUSTRIES CORPORATION

[8307c4]

My truck's 360 cid V8 doesn't feel the compressor, I can run it all I want.
Trucks are not like cars, their engines are designed to do one thing: Pull load.
And that is where 90% of the engine's energy goes, into pulling the load.
Even the best aerodynamics make small effect on a truck's fuel economy.

Why those square yellow brick school buses wouldn't get better fuel mileage if their front ends were more aerodynamic, their engines are pulling so many thousands of pounds of load that even the aerodynamics of a billboard hardly affect its fuel economy.

The only thing that affects its fuel mileage are speed variations, and their amount and intensity... The few things that frustrate me the most, other than folks tailgating, are drivers cutting me off, getting in the space in front of the truck without thought as to why that space exists other than they're trying to get to the proverbial finish line.

When a truck is following the car in front with a 4-6 second distance...
DON'T cut into the empty space in front of it!
It is the truck driver's "safe following distance."
It exists as a buffer, to help in case of sudden stops.
Not because it saves fuel, but because it takes that long TO stop!

When a truck is SLOWLY coasting to a stop light ...
DON'T cut into the empty space in front of it!
Doing so may force that truck to stop completely.
A truck coming to a complete stop wastes a tremendous amount of fuel re-accelerating.

My truck's mpg hovers between 10 and 11 miles per gallon.