Does the 2010 drive system work backwards?

Discussion in 'Gen 3 Prius Main Forum' started by Tech_Guy, Mar 15, 2009.

  1. ken1784

    ken1784 SuperMID designer

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    That's right high geared solution for better fuel economy.

    The Japanese sales staff manual says...
    At 120km/h(75mph) cruising..
    Iconic: ICE=2,470rpm FE=17.2km/L(40.5mpg)
    2010: ICE=2,180rpm FE=19.0km/L(44.7mpg) -> 10.5% improvement

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  2. bwilson4web

    bwilson4web BMW i3 and Model 3

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    This is great information! Thank you!
    Granted there will be some differences between the NHW11 and NHW20 but here is what I get for power required as a function of speed:
    [​IMG]
    At 75 mph, the power requirement is roughly 30 hp.

    So using my field data on the 1NZ engine:
    [​IMG]
    The 30 HP (right axis) gives an ICE rpm of ~2,525 rpm. This is pretty close to "2,470rpm" from the sales material. I suspect this reflects the smaller gearing of the NHW11. My NHW11 field tests indicates ~39 MPG at 75 mph, which is also close to the "40.5mpg" from the sales material.

    For the NHW20 owners, the ZVW30 (2010 model) will be a step up. For this NHW11 owner, it will be even more.

    Thank you Ken! It is nice to see my observations match at least the sales material.

    This means I can now concentrate on some of the obscure aerodynamic tweaks. Things that prove out on my NHW11 should also work for the ZVW30.

    Bob Wilson
     
  3. usbseawolf2000

    usbseawolf2000 HSD PhD

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    Even with the overall higher gearing, the 2010 Prius still accelerates about one second faster (in 0-60 mph) than the Iconic, thanks to more torque and power. If they kept the gearing the same, 2010 should accelerate faster but the highway MPG may be closer to the Iconic. I think chief Otsuka-san did a beautiful job balancing acceleration and MPG.

    As Bob's graph shows, the difference between 55 mph and 75 mph is double (15hp vs. 30hp) the energy needed to push through air. That extra 20 mph faster is not worth the extra 15 hp IMHO.
     
  4. ronhowell

    ronhowell Active Member

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    Exactly my thoughts too.

    The answer must be wrapped up in the economics of gear manufacturing, with which I am totally unfamiliar. But with what appears to be such a small difference between the Camry and Prius trans-axle gear sets I would have thought a common design would have provided economic benefits.
     
  5. ronhowell

    ronhowell Active Member

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    So true. The power required at any reasonable level of sustained speed being only 1/4 or less than required to provide what we call "good" acceleration shows where most of the fuel energy goes. So any means of regaining it while decelerating is a big plus, which is why Toyota deserves tribute for sticking to its guns with the HSD system. Gasoline, once burned, is gone for good.
     
  6. xs650

    xs650 Senior Member

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    With CNC gear cutting and relatively large quantities, the cost benefit of using one set of gears for both cars would be very small.
     
  7. coulomb

    coulomb Junior Member

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    Sorry for resurrecting an old post.
    Errrm... why do people seem to be assuming that the SRU (what does that stand for, BTW?) is a planetary gear. But there is only one input (MG2) and one output (the ring gear to differential connection). So surely it would be an ordinary gear pair, possibly meshing with an existing gear (say the outer part of the ring gear). Am I missing something?

    Edit: I can answer my own question, sorry. Per this post: http://priuschat.com/forums/gen-iii-2010-prius-main-forum/59089-mg1-rating-2.html#post807034
    they seem to us using a planetary gear for compactness, and so that the shafts remain in-line. It seems to re-use the *inner* ring gear teeth.

    Oh, and SRU = Speed Reduction Unit. Duh.
     
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  8. ken1784

    ken1784 SuperMID designer

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    two years late response, but...

    PSD
    sun: 30 teeth
    planet carrier: 23 teeth
    ring: 78 teeth

    SRU
    sun: 22 teeth
    planet carrier: 18 teeth
    ring: 58

    more than that, the SRU gear set is wider than PSD for supplying more torque.
    So, the PSD and SRU are different.

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    [​IMG]
     
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