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Go Back   Hummer Forums by Elcova > Hummer H3 Discussion Forums > Technical Discussion and Customizing your H3

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  #1  
Old 10-31-2006, 08:09 PM
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Default Re: H3 MPG < H2 MPG

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Originally Posted by Field Scout
IMO two things may be at play here, first is the diameter difference in tires, since w/315/75/16 you are going 3.5 mph faster than w/285/75/16 therefore farther distance traveled with each revolution your odo is not showing true distance making your mpg caculations off (to my knowledge no one recalibrates speedo for h3 as of this time) second when you went to 35's did you also go M/T I was getting about 17.5mpg on highway w/stock 33's, changed to 33 in bfg mt and dropped to 14.85 mpg on highway(higher resistance tire = worse mpg)


Just guessing, but another problem could be the torsion lift changing the aerodynamics of the front end and underbody.
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Old 10-31-2006, 08:39 PM
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Default Re: H3 MPG < H2 MPG

It's pretty obvious. The less MPG your vehicle gets, the cooler it is. The cooler your vehicle is, the less MPG it gets.
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Old 10-31-2006, 08:44 PM
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Default Re: H3 MPG < H2 MPG

Just did some calculations on your estimated tire diameter (C = pi * d). Assuming an actual diameter of 33 and 35 inches, your tire circumference changed from 103.62 to 109.9 inches, so you're now travelling 6.28 inches further with each tire revolution than your odometer reads.

To convert your mpg, find the ratio of one circumference to the other and multiply by your odometer's mileage.

109.9/103.62 = 1.06%

9 mpg * 1.06 = 9.5 mpg (corrected)

That's not very much. Maybe aerodynamics from the t-bar lift makes a bigger difference. Other factors could be tire pressure, cargo load and driving patterns.

Somebody please check my math. My algegra's a little rusty.
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Last edited by Wisha Haddan H3 : 10-31-2006 at 08:46 PM.
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Old 10-31-2006, 10:06 PM
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Default Re: H3 MPG < H2 MPG

Quote:
Originally Posted by Wisha Haddan H3


Just guessing, but another problem could be the torsion lift changing the aerodynamics of the front end and underbody.

I have a 5 turns on t-bar as well as roof rack w/pull pall and highlift jack I noticed a slight drop after t-bar crank (1/4 mpg) but never put crank/aerodynamics together. figured I was just getting a little more into the skinny pedal than before. major drop after I added M/T's
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