Gas mileage readout wacky now

XP900

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After upgrading to a Gen2R and putting in 1000cc injectors I notice my gas mileage readout is no longer reliable...seems to have an issue accurately displaying gas mileage.

At a steady drive at higher speeds it reads normal...but getting on the gas or sometimes stopping and starting it seems to think I am getting 4 to 8 mpg and seems to kinda lock into that mode for a while until I reset it. I tested my gas mileage and it is about normal....60-70 miles an it used about 1/4 tank in local driving.

As an example...say I drive 10 miles and it averages at 17mpg....I come to a stop and start up....it may suddenly slow 7 mpg and then very slowly go back up...but at a really slow place ..are the 1000cc injectors (95lb DW) the issue, the tune or is it normal now and I just live with it??
 

HKusp

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I believe it is the tune, I don't pay attention to mine in the GT500 at all, but in my Superduty, once they are tuned, the "lie-o-meter" is notoriously inaccurate. In my GT500, I just watch the tripometer to know I am getting 200-220 miles per tank in mixed driving.
 

SCGallo2

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With a new PCM calibration file, you should confirm that your rear gear and tire revs per mile were programmed correctly in the tune by using GPS to verify that your speedometer is correct.

Separate but related to your issue, the fuel range to empty always bothered me, because regardless of the fuel level in the tank, when the computer thinks you have 50 miles remaining, you get a low fuel light and warning. One way to re-baseline the fuel range is to fill up the gas tank completely full and then do a Keep Alive Memory (KAM) reset with your handheld programmer. Cruise around normally for the first ½ tank or so to get your average fuel mileage up, then have fun. This procedure appears to work well for me with my custom tuning.
 

XP900

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I have the same issue with the VMP and the tuner's tune with the new parts. I am starting to think it is related to the 95lb DW injectors used with the tunes since the BAPs were not used originally with the VMP tune the first time I test drove it and noticed the issue. My actual gas mileage does not appear to have changed very much. I can live with it. The speedometer matches my GPS readout too so gearing and tire size settings are probably correct.
 

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