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Speedometer

Discussion in 'Gen 1 Prius Plug-in 2012-2015' started by Jcone, Sep 1, 2014.

  1. CharlesH

    CharlesH CA HOV Decal #5 on former PiP

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    The raw data on the OBD-II bus is correct, but the speedometer readout is programed to read high. Or so I have heard.
     
  2. Lourun

    Lourun Member

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    My odometer is off by same ratio as speedo 3%
     
  3. fuzzy1

    fuzzy1 Senior Member

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    How are you measuring it? Are you still using the OEM tires?

    Over a 90 mile stretch of I-90 in Washington State, starting just past a known 'bust' between mileposts 218 and 219 (just 0.4 mile apart), my odometer differs from the mileposts by between 0.1 and 0.2 miles.
     
  4. rxlawdude

    rxlawdude Active Member

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    So your warranty is for 3% fewer miles than stated. You might wish to notify TMC about that, and get a written extension of your warranty.
     
  5. GregP507

    GregP507 Senior Member

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    It should be a no-brainer with today's technology to have accurate speedometers. The inaccuracy leads one to speculate on a possible motive.
     
  6. Jcone

    Jcone New Member

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    Is the speed of modern vehicles still derived the old fashioned way from the axle rotational speed and tire geometry?
     
  7. ggcc

    ggcc Member

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    This morning, I checked 20MPH on my 2014 PiP --> 18MPH on Scangauge.
     
  8. john1701a

    john1701a Prius Guru

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    Watch this video. There are more factors at play than are apparent. The ODB-II data gets rather funky on some changes during slower speeds.

    I didn't realize the effort Toyota made to smooth out the readings. Being a little high at times sure beats it being way off like that.

     
  9. GregP507

    GregP507 Senior Member

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    3000 miles for every 100k?
    Why not?
     
  10. rxlawdude

    rxlawdude Active Member

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    Why not what? :)
     
  11. GregP507

    GregP507 Senior Member

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    Why not try to get extra warranty?
     
  12. Earthrise

    Earthrise New Member

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    I have driven many rental Prii in the US and my own Prius PiH in Europe and I noticed that the speedometer reading for the European Prius appears to be significantly more "optimistic" than for US models:

    A Swiss review of the PiH highlights this wide difference:

    90 km/h (effective) at 100 km/h (indicated) [=-10%]
    113 km/h (effective) at 130 km/h (indicated) [=-13%]

    whereas in the US, it is always within 2 mph of reality.

    On the other hand, I found that the odometer readings (and fuel consumption stats!) were remarkably super accurate. So this excludes the 15" vs. 17" wheel size being a significant factor.

    I think Toyota deliberately programmed the speedometer in this way, not so much to "protect" their drivers from speeding tickets (we are talking about Prius drivers after all :) ) but to encourage us to drive slower, at more fuel-efficient speeds. This will be significant at motorway/freeway speeds (since fuel consumption will be much influenced by wind resistance that is proportional to the square of the speed - e.g. twice as much aerodynamic drag at 75mph than at 50mph.)
     
  13. rxlawdude

    rxlawdude Active Member

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    That, and federal law requires speedometers to have an optimistic bias.
     
    Mendel Leisk likes this.
  14. Lourun

    Lourun Member

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    I lease and will easily be under my milage allowance, so I don't care!
     
  15. rxlawdude

    rxlawdude Active Member

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    But that means your mileage limit under the lease is effectively smaller than it would be with an accurate ODO. :)