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Scangauge Miles vs Odometer

Discussion in 'Gen 2 Prius Technical Discussion' started by tom1l21, Jun 12, 2010.

  1. tom1l21

    tom1l21 Member

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    After driving 554 miles and 63.2 MPG read from MFD, my scangauge reads that I only traveled 548 miles with 62.6 MPG. How come the distance traveled isn't the same? What determines how both the Prius and the scangauge determine distance traveled? I know the prius usually reports +3MPH over for safety, is this factored into either the Prius' internal computer or the scangauge? I'm curious on how this information is calculated. Thanks!
     
    #1 tom1l21, Jun 12, 2010
  2. fuzzy1

    fuzzy1 Senior Member

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    My Prius trip meters are also showing higher mile counts than the ScanGauge on recent commutes. This wasn't noticed earlier partly because I don't normally use ScanGauge's trip odometers. But earlier highway tests found my Prius trip meters very accurate, reading roughly 0.2% low. I haven't yet determined whether something has changed, or the Prius reads different in stop-and-go city traffic than on the open highway, or the Scangauge is off.

    ScanGauge obviously knows only what Prius tells it. Since Prius knows its real speed, ScanGauge can report the real figures unhampered by the industry standards and legal requirements to display a higher speed. I don't know of reasons why the two display different distances.
     
    #2 fuzzy1, Jun 12, 2010
  3. 2009Prius

    2009Prius A Wimpy DIYer

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    I would say ScanGauge is not perfect. Many times after the car is powered off, the ScanGauge trip MPG or average MPH would change by one least significant digit.
     
    #3 2009Prius, Jun 13, 2010
  4. linuxpenguin

    linuxpenguin Active Member

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    My best guess is that it has something to do with tire size compensation. I know that the speed that the ECUs think the car is going is sometimes off from what the speedometer on the dash shows (using a scan-tool to pull values). The value on the speedometer would of course be compensated for tire size (it's a dealer calibration).

    Can anyone verify this with the scangauge (I don't have one)? If you select vehicle speed as a gauge--does it match up perfectly with the speedometer? That would explain the difference in distance traveled...

    Andrew
     
    #4 linuxpenguin, Jun 13, 2010
  5. JHSmith

    JHSmith 2020 Avalon Hybrid Owner

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    Have you performed the distance and fuel usage calibrations on the ScanGauge? By performing these two simple functions, the SG should register accurately.
     
    #5 JHSmith, Jun 13, 2010
  6. fuzzy1

    fuzzy1 Senior Member

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    Duh. Its been two years since reading the manual, so I forgot that distance/speed can also be calibrated. Since this device was originally targeted to a completely different group of auto enthusiasts, it needs this feature to accommodate major changes in tire sizes, transmissions, and final drive ratios.

    Page 17 of the manual:
    "MORE>SETUP>SPEED
    Both speed and distance can be adjusted to compensate for changes in
    tire size, gears, tire wear, etc. ...
    The right and left upper buttons can be used to increase/decrease the
    selected adjustment in 1% steps."

    And don't forget to SAVE.
     
    #6 fuzzy1, Jun 14, 2010
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