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Old 01-05-2008, 03:08 PM   #8 (permalink)
Chronologically Gifted
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Join Date: Jan 2008
Location: Corvallis, Oregon
Posts: 42

Base Metro - '96 Geo Metro
90 day: 54.24 mpg (US)

Neon ACR - '98 Dodge Neon ACR

Banana Slug - '64 Volkswagen Bug

Spirit - '92 Toyota Class C Motorhome Winnebago Itasca
90 day: 17.26 mpg (US)
Thanks: 8
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Okay, it's starting to make a little more sense now... The ECU is overthinking the situation and correcting for what it sees as problems. If the computer didn't do so many "favors" for us we might be able to tweak our engines more for better economy. Maybe not. Maybe I'm just too "old school." Generally it seems like the computer does a pretty good job of keeping the mixture in a reasonably good range most of the time; a lot better than most old carburetors did. But like most car design features, it is a compromise for the average driver under average conditions.

I'm not an average driver, and I'm guessing you're not either. It looks like, as you suggested, I'll have to figure out what the computer likes best and then try to duplicate that condition. Still, I'd like to be able to adjust the computer for what I think it should do, and then verify it myself. (I plan to get one of those cool Scan Gauge II's).

I think your advice is right, considering things as they are. I'll have to test to find out what intake air temperature works best for economy and try to provide that to the intake air sensor. Maybe at some point I can figure out how to trick the sensor and get colder air into the engine without the computer knowing about it, and see what that does...

Thanks for the explanation, and if I try anything along those lines I'll post the results on the forums here.

BTW, I will be driving a 96 Metro 2dr HB base model. No options, 3cyl 5spd. So far I have put less than 5 miles on it in the week that I've had it; I drive very little; mostly I am on foot. It runs kind of rough; I don't know if that's typical for a 3cyl or what. (any ideas?) I am mainly concerned with saving gas for geopolitical and environmental reasons, so it wouldn't make much sense for me to drive the car just for fuel economy testing purposes. That said, I won't give up my autocrossing so easily... Fo that I have a factory stock 98 Neon ACR (American Club Racer version). It actually gets decent mileage considering it has lower gears (3.94 final drive) than the standard models (3.55). It's a 2.0 liter DOHC, with few options so it is fairly light.

"Life is like a 10-speed bike. Most of us have gears we never use."
-- Linus
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