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Old 01-25-2012, 11:58 AM   #1 (permalink)
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Scangauge questions

I finally took the plunge on a Scangauge II after several years of thinking about it. I've been using it for a week now and have a few questions that I haven't been able to find answers to.

1. Under deceleration the manual says to change the setting for decel fuel cutoff to something like 4 less than the TPS reading when the throttle is closed. Otherwise it says it will read "9999MPG" under decel in gear. When I installed it for the first time, it would read 9999 under deceleration (which makes perfect sense to me, if it can't display infinity). So I change it as instructed and now it tells me that the car is getting 120-250 miles per gallon when decelerating in gear, even at higher RPM. That reading doesn't make any sense -- if it's using zero fuel and moving, why would it not read infinity, or 9999? Should it say something else when in fuel cutoff?

2. When installed in my other car (primary car), the MPG reading is erroneous. I log mileage religiously and lately have been averaging 26-28 miles per gallon and have never recorded a tank less than 25. But on my normal commute today it tells me that the trip average is just a hair over 20. The instantaneous MPG reading supports this and even at low highway speeds in top gear it only reads about 24. I'm not interested in the "tank" logging features on the Scangauge, but do I have to calibrate the MPG reading this way to make it agree with the MPG I calculate with the odo and receipt? In the first car it agreed with the gas log very closely.

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