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Gen III MG2 RPM vs MPH

Discussion in 'Gen 3 Prius Technical Discussion' started by jdcollins5, Nov 9, 2011.

  1. jdcollins5

    jdcollins5 Senior Member

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    I have just recently installed a ScanGaugeII on my car and have been intrigued with the HSD and learning all that I can about this amazing vehicle.

    I have a 52 mile RT commute each day on a 55 mph speed limit highway and of course run on cruise control at 60 mph. I have noticed that the MG2 RPM = 7000 at 60 mph displayed. So I began to do some research here on PC to determine the gear ratios and the relationship between MG2 rpm and mph.

    I came across an earlier thread where there were discussion of the improvements of the Gen III over the II. I came across a post by HTMLSpinnr where he gives the gear tooth counts of the complete HSD system.

    I have taken those gear tooth counts and applied them to the MG2 RPM of 7000 to calculate MPH based on my tire rev/mile. I also found out that the max MG2 rpm = 13500. When using the gear ratios this works out to the Prius max speed of 113 mph.

    I thought that other newer PC members like me may be interested in these calculations. If anyone sees any errors in my calculations please let me know.
     

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    #1 jdcollins5, Nov 9, 2011
    70AARCUDA, usbseawolf2000, tumbleweed and 1 other person like this.
  2. tumbleweed

    tumbleweed Senior Member

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    That explains why the top speed is electronically limited to 112.
     
    #2 tumbleweed, Nov 10, 2011
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  3. vincent1449p

    vincent1449p Active Member

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    With the addition of SRU, the speed relationship for MG1, MG2 and Engine has to be updated.

    Equation 1:
    ws = ( 1 + R ) * wc - R * wr

    where
    ws = Angular speed of Sun gear = MG1 RPM * 2 Pi() / 60 rad/s
    wc = Angular speed of Pinion gear = Engine RPM * 2 Pi() / 60 rad/s
    wr = Angular speed of Ring gear = ( MG2 / S ) RPM * 2 Pi() / 60 rad/s
    R = Gear Ratio of PSD = 78 / 23 * 23 / 30 = 78 / 30
    S = Gear Ratio of SRU = 58 / 18 * 18 / 22 = 58 / 22

    Converting all rad/s to RPM and substitude into Equation 1,

    MG1 = ( 1 + R ) * Engine - R * MG2 / S

    MG1 = ( 1 + 78 / 30 ) * Engine - ( 78 / 30 ) * ( 22 / 58 ) * MG2

    MG1 = ( 30 + 78 ) / 30 * Engine - ( 13 / 5 ) * ( 11 / 29 ) * MG2

    MG1 = ( 18 / 5 ) * Engine - ( 143 / 145 ) * MG2

    MG2 = ( 145 / 143 ) * ( ( 18 / 5 ) * Engine - MG1 )

    Engine = ( 5 / 18 ) * ( MG1 + ( 143 / 145 ) * MG2 )

    Vincent
     
    #3 vincent1449p, Nov 13, 2011
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  4. jdcollins5

    jdcollins5 Senior Member

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    Thanks Vincent

    Now does anyone know how to convert the Gen II HSD animated graphic with these numbers to make a new animated Gen III graphic ??
     
    #4 jdcollins5, Nov 18, 2011
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