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Old 09-16-2014, 02:15 PM   #8 (permalink)
eco-jeeper
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Join Date: Sep 2014
Location: Columbia, SC
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Old Blue - '93 Jeep Cherokee
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Thanks elhgih, will do!

Quote:
Originally Posted by oldtamiyaphile View Post
You assume that the speedo and odo are calibrated the same, they're not on any vehicle I own.

Your odometer was accurate from the factory to about 1%, it probably now under reads by ~10%.

When you put 31's on a standard Jeep XJ/TJ, you end up with an accurate speedo (about 1% over reading), but the odo now under reads by around 10%.
Like I have shown, my theoretical speed (speedo x 1.12) was equal to my ACTUAL speed in a one-mile time test, to within 1%. Your speedo might have been 5% over, mine is apparently less.

As far as the odometer output I'll have to test that separately over a longer stretch of interstate, but for now I simply calculated my MPG as miles * 1.12 / gallons. No calculation like this is going to be perfect, but the variance between the speedometer and odometer is likely negligible, if the odometer was indeed factory accurate within 1%, and the speedo*1.12 at this time is accurate within 1%.
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