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MG Torque Vs. ICE Torque?

Discussion in 'Gen 3 Prius Technical Discussion' started by OZ132, Jul 29, 2009.

  1. OZ132

    OZ132 Member

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    If I read the specifications correctly, Motor (MG) Torque on the Generation III is about 1/2 the torque of the Generation II? Circa 150 foot pounds vs. 300 foot pounds? The new ICE, of course, is bigger, hence produces more torque than the Generation III? But at Zero MPH, don't you need max torque to get rolling, just when the ICE is at Zero torque?
    But overall performance (0-60) is improved, as is MPG?
    Any of you Techies want to take a shot at an explanation of how this works?
    I assume they run the new Motor (MG) faster, perhaps utilizing a bigger gear reduction to make up for the big drop in low speed torque? Of course, Horsepower = Torque times Speed, but then, what? After that, I'm lost.
    I am truly fascinated by the elegance of the design of the Hybrid Synergy Drive. So much is counter-intuitive. The Generation III improvements once again challenge my knowledge and imagination, including this cutting Motor torque in half, while improving acceleration. For all I can tell, it's all done with mirrors...
    :confused::confused::confused::confused::confused::confused::confused:
     
    #1 OZ132, Jul 29, 2009
  2. qbee42

    qbee42 My other car is a boat

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    MG2 is now geared, which multiplies the torque. The torque at the shaft of MG2 is lower, but it spins at a higher speed. Overall MG2 is more powerful with the Gen III.

    Tom
     
    #2 qbee42, Jul 29, 2009
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  3. ken1784

    ken1784 SuperMID designer

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    Gen2:295lb-ft(MG2 torque) X 4.113(final gear ratio) = 1213lb-ft(torque at wheels)
    Gen3:153lb-ft(MG2 torque) X 2.636(reduction gear ratio) X 3.267(final gear ratio) = 1318lb-ft(torque at wheels)

    Ken@Japan
     
    #3 ken1784, Jul 30, 2009
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  4. rwilsont1

    rwilsont1 Junior Member

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    Thanks, Ken this is very helpful. I am a physicist trying to understand the CVT. Could you post the gear ratios for the ICE and MG1. This and the max rpm of MG1 would complete what I would like to know
     
    #4 rwilsont1, Aug 4, 2009
  5. David Beale

    David Beale Senior Member

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    Do remember that the maximum torque of the motor is limited by the battery. It isn't allowed to deliver full current to increase its' life. So if the engine isn't running (that is, there will be no current supplied by MG1) then all current must come from the battery, and it's limited. As I recall it results in about 2/3 the MG2 max torque.
     
    #5 David Beale, Aug 4, 2009
  6. ken1784

    ken1784 SuperMID designer

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    The gear ratio of the planetary gear set is little tricky. :)
    planet carrier (ICE): 23 teeth
    sun gear (MG1): 30 teeth
    ring gear: 78 teeth

    MG1 rpm = 3.6 * ICE rpm - 2.6 * ring gear rpm

    These numbers are unchanged among Prius generations (Gen1 to Gen3)
    For more information, please refer to the great Graham's site...
    The Power Split Device

    We don't know the max rpm of MG1 on the Gen3 yet, but it is 10,000rpm on the Gen2.

    Ken@Japan
     
    #6 ken1784, Aug 4, 2009
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  7. a64pilot

    a64pilot Active Member

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    My head hurts now
     
    #7 a64pilot, Aug 6, 2009
  8. snead_c

    snead_c Jam Ma's Car

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    Mine too.. :blink:
     
    #8 snead_c, Sep 1, 2009
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