Quote:
Originally Posted by MetroMPG
Does this only apply to an engine operating in closed loop mode?
This is one of the drawbacks of the ScanGauge, in my understanding. It's relatively accurate provided you stay in closed loop, where it can make calcs based on stoich A/F ratios. But when you get into open loop fuel enrichment at higher loads, it doesn't necessarily know how much more fuel the computer is injecting.
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In my experience, this is where the ScanGauge falls flat, but only in reporting Instantaneous MGP. Last summer, I drove my F350 Diesel on a 1600 mile round trip over two long days, pulling a big, heavy, very un-aerodynamic trailer over a lot of long steep hills. In the steepest parts, to keep the speed above 50mph I had to use full throttle. During full throttle, the ScanGauge would indicate the instant-mpg at crazy numbers: 53mpg, 217mpg, 9999mpg, etc. The numbers would jump all over the place. At one point, I was at full throttle (never lifting) for over an hour... But the average MPG was correct, and at the end of the tank, it was only off by 1/10th of a gallon, on the pessimistic side. If they can get the average correct, I don't know why they can't get the instant correct.
FWIW.