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I realize that our little Fortwos operate the throttle body by the "drive by wire" system. A rheostat in the accelerator pedal sends a signal out to the ECU I guess that translates that signal to voltage to drive a small motor that opens and closes the throttle body.
I know there are "enhancement" pedals from the Go pedal to things from Smart Madness to enhance throttle response. My Fortwo doesn't have these enhancements. It is totally stock. I have noticed in the extreme hot temperatures we have been having and the A/C on it tends to have a flat spot. When driving above 40 mph and I come to a hill that is a long grade, you push the gas feed down and the engine begins pulling. You can start up the hill and naturally you lose some speed or maintain your speed. If I shove it down just short of causing it to backshift it labors along, but it pulls. If I in turn THEN back off the throttle a little it pulls even harder as though I gave it MORE gas.
I know I really ask alot of it with a/c and West Virginia hills are pretty steep and hot weather makes it even harder, but does anyone else notice anything like this? It normally pulls really good above 3,000 rpm's and power normally is pretty good since my valve replacement, but really warm weather and A/C seems to heat up the engine enough to cause a flat spot. DCO
 

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The air conditioning compressor is a pretty significant drag on the engine, and it's being used when it's hot and humid, i.e. low air density, i.e. engine is making less power on that account alone. It's not just the drive-by-wire.

I don't know if it is a variable-displacement compressor. If it is, the drag on the engine will vary depending on how much demand there is on the A/C system. If it is a fixed-displacement compressor, the drag on the engine will vary as the compressor cycles on and off.

Unfortunately, it's been a couple of years since I've felt this. (mine stopped working)
 

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I go through WV quite frequently, max A/C, passenger and dog, "stuff"...........
I just downshift a LOT in WV and all is "cool" :cool:
 
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