Gen 3 owners with 45 mpg+ Question

Discussion in 'Gen 3 Prius Fuel Economy' started by Darklandscape, Nov 1, 2022.

  1. nicoj36

    nicoj36 Member

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    Do you have sources to prove that EV mode actually burns more gas than regular mode?
     
  2. Mr. F

    Mr. F Member

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    IV
    This can actually be solved without hard numbers/sources.

    In ICE-only mode, gasoline is burnt to produce shaft power (step 1) which drives the wheels.

    To run in EV mode, gasoline has to be burnt by the ICE to produce shaft power (step 1), which drives MG1 to generate electricity (step 2), which must be stored in the HV battery (step 3), which is used by MG2 to drive the wheels (step 4).

    The net efficiency of either of these modes is the product of the efficiencies of the individual steps. And since each of the steps is less than 100% efficient, the best way to minimize losses (maximize efficiency) is by picking the mode that doesn't have the additional efficiency-reducing steps. Therefore, for a given amount of fuel burnt, ICE-only will get you further than EV-only.

    In the normal course of action, the car decides for itself how much of the shaft power must be split between MG1 and MG2 to maximize the overall efficiency of the vehicle. Forcing it to run in EV-only or ICE-only modes will yield worse MPG numbers than if you let the car decide.
     
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  3. ChapmanF

    ChapmanF Senior Member

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    There may be occasional situations where a hint from you can help the car decide better. For example, if approaching such a long downhill that the battery will reach full charge whatever happens, using B will hint that the car can charge the battery more gently and still recapture as much energy as it can. But giving the same hint other times when it's not on point would likely reduce your overall mpg.
     
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