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DIC vs hand calc mileage differences

J

jackh

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so i took a trip out to east texas and decided to do some mileage testing with my new quadzilla. before starting, i loaded on the economy tune. by the end of the drive out there, the DIC said something like 17.1 mpg and when i filled and hand calculated i got 17.27 ish, no biggie. however, when i left to come back home, i loaded on the 90 tune to see if my mileage was better (and i liked the extra hp to pass ppl :) ). by the time i got home, my DIC read 20.1, i was feelin good lol. when i filled and hand calculated i got 17.4 though.... i can see a small difference in DIC and hand calculated measurement like what i got on the way there but i dont see how there was such a big difference in the trip home. anybody know why? and before you ask, i reset my trip and average fuel economy after filling up on the trip there and back to keep the DIC as acurate as possible.
 
on the higher tune when you were "passing" people it probably sucked a lot more fuel than the DIC said
 
bigBOOST said:
on the higher tune when you were "passing" people it probably sucked a lot more fuel than the DIC said
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well i like the extra hp but i was tryin to get real good mileage so i didnt do any of that

whatnot said:
The DIC is calibrated to the stock tune. You change it and it calculates wrong.
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that makes the most sense so far. the economy tune is way closer to stock than the 90 so naturally the DIC and hand calc mpg's would be closer.
 
The calculations in the DIC are just estimations, even on a completely stuck vehicle they can be off by as much as 3 mpg. My truck is always off by about 2 mpg even on stock settings. My mom's Impala is the same way and it fluctuates.
 
so the DIC is basically worthless?

anybody know why this is?? seems like if you reset the DIC everytime you filled up if you were gonna test mileage at the end of that tank the DIC would be somewhat accurate..
 
Mine is pretty accurate for the most part. Maybe I'm lucky..
 
jackh said:
so the DIC is basically worthless?

anybody know why this is?? seems like if you reset the DIC everytime you filled up if you were gonna test mileage at the end of that tank the DIC would be somewhat accurate..
Click to expand...
Yes it's very inaccurate depending on your particular setup. BUT, it's usually fairly repeatable so it will tell you how you're doing verses a comparable period of driving. Does that make sense?...
Mine is always off by a good 3mpg or so even after I do the correction for the 285s. I have calculated every refuel mpg since day one and I can pretty well estimate what mpg it will be from looking at the DIC ave mpg #.
 
Mine is very close as well. On a trip to Tucson AZ. Thanksgiving I tested it and it was off less than a .5 mpg. The mileage seemed to be spot on. I will have to change to a higher tune and see if it skews like your did.
 
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