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Better speed measurement

Discussion in 'Gen 2 Prius Technical Discussion' started by kkayser, Jan 12, 2010.

  1. kkayser

    kkayser Junior Member

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    Does someone know a way I can determine if my '04 is accelerating or decelerating? This would be while I am coasting. It is easy with an analog speedometer, by just looking at the direction of needle movement. The digital speedometer is not sensitive enough. I do not need more accuracy; I need something that will tell me if my speed is increasing or decreasing by 0.1 mph or less.
     
    #1 kkayser, Jan 12, 2010
  2. CharlesJ

    CharlesJ Member

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    I don't have an answer for such capability but you are implying that you can tell such small changes 0.1 mph or less, on an analog speedometer? WOW.
     
    #2 CharlesJ, Jan 12, 2010
  3. kkayser

    kkayser Junior Member

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    It is not difficult; I just need to see the needle move in one direction or the other. I observe the position of the needle with respect to the position of the speed markings on the dial. Depending on the speedo, it might be .2, .3 MPH, whatever, but more sensitive than a digital.
     
    #3 kkayser, Jan 13, 2010
  4. ken1784

    ken1784 SuperMID designer

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    There is the SPD signal (D-19) on the Hybrid ECU.
    You can measure its frequency using $10 digital multimeter with frequency measuring capability.
    The frequency at 60 km/h (37.3 mph) is 42.47 Hz.

    The ECU connector picture for RHD(JP) Prius is shown below.
    Maybe, the connector positions are upside down on the LHD(US) Prius. :)

    Ken@Japan

    [​IMG]
     
    #4 ken1784, Jan 13, 2010
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  5. kkayser

    kkayser Junior Member

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    thanks you very much!:cheer2:
    I do have a multimeter which measures frequency. How can I access that point?
     
    #5 kkayser, Jan 13, 2010
  6. Doc Willie

    Doc Willie Shuttlecraft Commander

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    I believe there are some ScanGuage X-guage settings that read some of teh accelerometers in the Prius.
     
    #6 Doc Willie, Jan 13, 2010
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  7. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Find the hybrid vehicle ECU which is behind the glove box. Then find pin 19 as cited by Ken. The wire should be violet.

    Splice into that wire and measure from that point to ground, using your frequency meter.
     
    #7 Patrick Wong, Jan 13, 2010
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  8. ken1784

    ken1784 SuperMID designer

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    #8 ken1784, Jan 13, 2010
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  9. Oddest_raindrop

    Oddest_raindrop New Member

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    well It's hard to believe that one could tell tenths of a mile per hour with an analog. But if someone must you could get a scangauge for which there is an x gauge that will update the mph very frequently with tenths of a mph. This passive gauge would work.
    GAUGE TXD RXF RXD MTH NAM Notes
    Miles per Hour 00BC 010042B40000 380C 08D80E930000 mph xx.xx mph
     
    #9 Oddest_raindrop, Jan 14, 2010
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