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??Can this be true??

Discussion in '4 Cylinder' started by zbouncer, Aug 10, 2011.

  1. Aug 10, 2011 at 10:23 AM
    #1
    zbouncer

    zbouncer [OP] Well-Known Member

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    I have a 05 prerunner 5spd 2.7 2wd with the access cab, it had a 3" spacer kit from revtek and 285/75/16 BFG Mud and was getting 15.7mpg on first tank not really worried about gas driving. So I started driving more gas conscious and only got 16.1 next tank. Thinking it was the meats I bought some 265/74/16 Hankooks and switched from the revtek to 5100s all the way around and kept shifts @ 2500, but only yielded 16.9mpg! Have all mobile1 synthetic fluids in motor, trans, and dif, NGK plugs and not to mention I just installed a new air filter that is strongly recommended on this site. I'm not expecting 35mpg like my Yaris did, but what the deal with my bad mpg :confused:
     
  2. Aug 10, 2011 at 10:28 AM
    #2
    97yota4wd

    97yota4wd Well-Known Member

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    alot of metal, small engine, decent travel.
    caged, camburg long travel, 50t leafpack (soon to be installed) light rack over cab, 5pt harnesses etc
    hmm idk... you should be getting around 20
     
  3. Aug 10, 2011 at 10:31 AM
    #3
    zbouncer

    zbouncer [OP] Well-Known Member

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    That is what I was going for when I bought it, I know there was this big deal about the thermostat on the FJs causing bad MPG because it stayed in the open position never letting the motor reach operating temp causing RPMs to constantly stay higher and the comp telling the injectors it needed more fuel. So maybe need new thermostat :confused:
     
  4. Aug 10, 2011 at 10:40 AM
    #4
    97yota4wd

    97yota4wd Well-Known Member

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    alot of metal, small engine, decent travel.
    caged, camburg long travel, 50t leafpack (soon to be installed) light rack over cab, 5pt harnesses etc
    okay heres how to check that....


    when the truck is completely cold, take the radiator cap off, start it, then run around to look at the fluid inside of the radiator, if it starts flowing instantly its stuck open, if it takes about 2-5 min its fine
     
  5. Aug 10, 2011 at 10:57 AM
    #5
    Pugga

    Pugga Pasti-Dip Free Since 1983

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    Did you correct the mileage for the larger tires?
     
  6. Aug 10, 2011 at 12:25 PM
    #6
    zbouncer

    zbouncer [OP] Well-Known Member

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    great DIY diagnostic..Thanks! :)
     
  7. Aug 10, 2011 at 12:26 PM
    #7
    zbouncer

    zbouncer [OP] Well-Known Member

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    Nope I did not, do you have a DIY diagnostic for that :confused:
     
  8. Aug 10, 2011 at 12:34 PM
    #8
    cummins6speed

    cummins6speed Well-Known Member

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    (old tire diameter-new tire diameter)/old tire diameter.

    That gives you a correction factor then multiply that by your trip milage to get your actual
     
  9. Aug 10, 2011 at 12:36 PM
    #9
    OZ-T

    OZ-T All of those moments....will be lost.....in time

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  10. Aug 10, 2011 at 12:41 PM
    #10
    zbouncer

    zbouncer [OP] Well-Known Member

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    285/265 = 1.08 x 287= 309.96/17= 18.23MPG

    I think that is correct, I feel a little better now, but am I still off beat of MPGs for my application :confused:
     
  11. Aug 10, 2011 at 12:42 PM
    #11
    97yota4wd

    97yota4wd Well-Known Member

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    alot of metal, small engine, decent travel.
    caged, camburg long travel, 50t leafpack (soon to be installed) light rack over cab, 5pt harnesses etc
    nope thats about right. better than i get in my 4 cyl with 31s haha
     
  12. Aug 10, 2011 at 12:45 PM
    #12
    OZ-T

    OZ-T All of those moments....will be lost.....in time

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    285 and 265 are the width of the tire not the diameter

    Trust me , use the site's tire calculator , there's a link on the home page
     
  13. Aug 10, 2011 at 12:50 PM
    #13
    zbouncer

    zbouncer [OP] Well-Known Member

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    Oh shit your right! :facepalm:

    So should I calculate off of the factory tire diameter (since that is what the comp is calculating miles off of) vs new diameter?
     
  14. Aug 10, 2011 at 12:54 PM
    #14
    OZ-T

    OZ-T All of those moments....will be lost.....in time

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    Go to the tire calculator , input the two tire sizes you are comparing , use the % adjustment between the two sizes to correct your mileage
     
  15. Aug 10, 2011 at 1:04 PM
    #15
    zbouncer

    zbouncer [OP] Well-Known Member

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    Ok here we go...

    Formula 1 based off stock tire vs current:

    1.18 x 287= 338.66/17= 19.92MPG

    Formula 2 based off BFG vs current:

    -1.18 x 287= -338.66/17= -19.92MPG

    I'm going to say its prob Formula 1 which means the comp reads miles based on stock tire size, which makes sense if it does this off of RPMs as well, so I am currently shifting at a much lower RPM?
     
  16. Aug 10, 2011 at 4:27 PM
    #16
    cummins6speed

    cummins6speed Well-Known Member

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    The "old tire diameter" number should be your stock tires, that is what the speedo and odometer are calibrated to.
     
  17. Aug 11, 2011 at 8:55 AM
    #17
    zbouncer

    zbouncer [OP] Well-Known Member

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    Correct :burnrubber:
     
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