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Analyze this - Mr Scangauge says:

Discussion in 'Gen 3 Prius Technical Discussion' started by tedjohnson, Sep 1, 2010.

  1. tedjohnson

    tedjohnson Member

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    So while doing a few nice long coasts, I tried to ascertain the D vs N facts. Going along an even decline at 45-65 mph with gas pedal feathered to eliminate regen. I see RPM=992, HP=4.8. Then quickly shifting to N gives me RPM=1100, HP= 2.6. Huh ??? Is this real or a problem with how Scangauge reads HP. IF the data is real then coasting in N should use less gas than the equivalent feathered coast in D. 5 tries at this all produce the same result. If true this says that the software guys protected the MG! better in N than in D, but why the drop in HP used - that makes no sense. Ted
     
    #1 tedjohnson, Sep 1, 2010
  2. qbee42

    qbee42 My other car is a boat

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    It sounds plausible. In both cases the ICE should be running, consuming a small amount of gas to keep turning. The control setpoints are probably somewhat different, since there is no strong reason they need to be identical. In D there is probably a small amount of power being sent to the wheels or the HV battery, accounting for the increase in HP. Scangauge isn't perfect, and probably misses this subtle distinction.

    Tom
     
    #2 qbee42, Sep 1, 2010
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  3. priuscritter

    priuscritter I am the Stig.

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    my post here is really unhelpful, but it seems as though i read somewhere not that long ago that neutral actually uses more gas than coasting while in gear. your tests sort of proved that by having lower RPMs while in gear. i can't speak to the HP issue, but I'm pretty sure the lower the RPMs, the less gas used.
     
    #3 priuscritter, Sep 1, 2010
  4. ken1784

    ken1784 SuperMID designer

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    FYI,
    There are discussions about gallons/hour number at greenhybrid.com.
    It seems Scangauge has some limitations.
    Ken@Japan
     
    #4 ken1784, Sep 1, 2010
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