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Speedometer

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

  1. Jcone

    Jcone New Member

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    Just curious whether all PiP speedometers have a +2-3 mph bias. For me it's 2 out of 2 (both 2014 model).
     
  2. rxlawdude

    rxlawdude Active Member

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    Yep. And it's a bit squirrely that in my '04 and '11, if I set the cruise control to 70mph, the speedo would almost always match that setting. On the '14 PiP, the car gets up to 72mph on the display pretty routinely. It's irritating but not significant.
     
  3. bisco

    bisco cookie crumbler

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    ditto. been there, done that.:)
     
  4. Barbara R

    Barbara R Junior Member

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    What does +2-3 mean?
     
  5. bisco

    bisco cookie crumbler

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    off by 2 or 3 mph.
     
  6. Potorap

    Potorap Active Member

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    Yes it is 2 mph for me. However on 2011 prius changed tires and almost matched up.
     
  7. GregP507

    GregP507 Senior Member

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    Judging by the fact that everyone seems to be reporting the same speedometer error, it looks like Toyota has either planned this, or they have made the same mistake consistently. I'm seeing 2-3% more speed indicated than actual speed, therefore it's possible that this would translate to what appears to be 2-3% more miles per gallon of gasoline. Not a bad thing for advertising purposes.
     
  8. Tracksyde

    Tracksyde Member

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    Its planned, but not for the purposes you may think:

    Speedometer - Wikipedia, the free encyclopedia (takes you directly to the "international agreements" section)
     
  9. GregP507

    GregP507 Senior Member

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    I still think it's for purposes I described. An accurate speedometer should be the easiest thing to achieve in a car like the Prius.
     
  10. Tracksyde

    Tracksyde Member

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    But if every auto manufacturer abides by the "agreement", then that would make MPG relative amongst all vehicles.. which would defeat the purpose of doing it for MPG reasons. And while we're at it, why not just go for the maximum allowable. In the given example, at 80kmh, you can be off by as much as 15%. That would be quite a healthy bump in MPG.

    And as I mentioned in a previous thread where this topic came up, you also have tires issues to contend with. I agree that an accurate speedo should be do-able with today's technology. But how would you account for all the differences in tire rolling diameter amongst different manufacturers, not to mention regular tire wear.
     
  11. bisco

    bisco cookie crumbler

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    or maybe it keeps the car from under reporting speed in case of wear or tyre change, and getting a ticket for going 33 in a 30 when your speedo says 30.
     
  12. GregP507

    GregP507 Senior Member

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    I'm going to go out on a limb and say that the speedometer could be self-calibrated from the nav-unit, if they wanted it to be accurate.
     
  13. RRxing

    RRxing Senior Member

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    As mentioned in this and other threads about speedometer bias, in addition to the international agreement, no automaker is going to subject themselves to a lawsuit for under-reporting actual speed. I just realize that my speedometer reads 2-3 mph high, no big deal.
     
    Mendel Leisk likes this.
  14. Chazz8

    Chazz8 Gadget Lover

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    It is so easy for the Toyota to report a true (let's just say within %1 of Garmin gps) that they did. It is available via the dongle under the steering wheel with ScanGuage II or torque setup.

    I like that you reported +2 to 3 percent higher MPH rather than +2 to 3 MPH higher Greg, as I see the difference between the speedometer and the CAN BUS dongle based reading increase as speed increases.
     
  15. fuzzy1

    fuzzy1 Senior Member

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    That probably won't happen until Nav units become universal, rather than optional or trim-specific.
     
  16. ggcc

    ggcc Member

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    I have a Scangauge, my 2007 Prius is matching MPH with Scangauge MPH. My 2014 PiP is 3 miles OFF (3 Miles Higher than the Scangauge).

    - The 2014 PiP 70 MPH Scangauge 67 MPH
    - The 2014 PiP 55 MPH Scangauge 52 MPH

    I saw the ICE is kicked in when PiP speed o meter at 61 0r 62, Scangauge RPM is change from 0 to xxxx around 58 MPH.
     
  17. Chazz8

    Chazz8 Gadget Lover

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    How much is the PiP off at 20MPH?
     
  18. retired4999

    retired4999 Prius driver since 2005

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    Mine at 30 mph is about right on. At 65 mph it is about 2 mph slow. Just my best Est.
     
  19. rxlawdude

    rxlawdude Active Member

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    Except the ODOmeter is the only relevant device for MPG calculations. Instant speed indicated on the speedometer is not relevant whatsoever to fuel consumption.

    Although it seems counterintutive, the fact the SPEEDometer is off by +2-3% does not mean the ODOmeter is off by that same proportion. In fact, if it were, there would be lots of class action lawsuits for fraudulent early termination of warranty coverage.
     
  20. fuzzy1

    fuzzy1 Senior Member

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    Yup. Both Honda and Subaru were hit with such suits while I owned those cars, and both settled for warranty extensions.
    BTW, neither of those cars of mine had significant odometer errors.