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If EV mode light is off, does that mean the engine is engaged in some way?

Discussion in 'Gen 3 Prius Technical Discussion' started by KirkLand33, Sep 20, 2014.

  1. KirkLand33

    KirkLand33 New Member

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    Jul 19, 2014
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    Kirkland, WA
    Vehicle:
    2013 Prius
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    Two
    When traveling at higher speeds (over 45 mph or so) down hill, the "EV" mode light will turn OFF but the car monitor shows the engine is not running. Can anyone explain what is happening with the ICE?

    What is the difference between EV mode light ON vs OFF if the ICE is not supposed to be running?

    For example, I think I have noticed that when I'm running in EV mode and gaining speed down hill and the EV mode turns off (usually about 45 mpg), I feel the engine rumble like it engages and then disengages. But the monitor shows that the ICE engine never turned on.

    I'm a long time reader but first time thread starter. I have searched for an answer to this but have not been able to find it. Thanks for your knowledge.
     
  2. Mendel Leisk

    Mendel Leisk Senior Member

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    Vehicle:
    2010 Prius
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    Touring
    The engine does start turning, at speeds just over 70 kmh for me, think that's translating to the 45 mph you're noticing. I've read it's due to the transaxle's motors, MG1 and MG2, there's a limit on how fast they can spin, and if the car's engine spins it allows them to stay under that rpm limit.

    There's a longish hill we go down, can coast down while accelerating, can see this happening, both on the car's gauges and a ScanGauge. SG shows RPM jump from zero to 900 something, just after we pass 70 kmh. Still, SG continues to indicate no fuel being consumed, at least until I touch the gas.
     
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  3. David Beale

    David Beale Senior Member

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    The engine is turned by MG2 I think, and it is turned to ensure MG1 doesn't overspin, as Mendel said. No fuel is consumed. This also happens when not in EV mode, when the engine power is not needed, such as coasting down a hill. Also as Mendel said engine RPM is just over 900 RPM. You can feel or hear it start up and stop but it runs pretty quietly so you may not hear that. A Scangauge shows the RPM and the fact that no fuel is being injected, though the Scangauge doesn't believe "no fuel" is possible and adds a tiny amount to the display. ;)
     
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