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MPG display inconsistencies

Discussion in 'Gen 2 Prius Main Forum' started by pepa, Dec 21, 2004.

  1. pepa

    pepa New Member

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    Inconsistency #1:
    While engine is running and the car is not moving (warming up), the display says 0.0 MPG consuption. Does this perhaps explain the difference in MPG reported and actually measured (per tank)?

    Inconsistency #2:
    When the cold engine starts up in cold weather ( 10F and less ) and running for only about 5 seconds, slowly start driving. It is obvious from the sound of the gas engine that the vehicle is being propelled from battery only - the sound of the gas engine (pitch) does not change as it does when you do the same with engine warmed up. Yet - now the display says the consumption as 12 - 20MPG.

    No complains - just found this interesting. Software bugs (omissions) maybe?
     
    #1 pepa, Dec 21, 2004
  2. efusco

    efusco Moderator Emeritus
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    That's normal and correct. Think about it, you're not moving at all...no matter how much fuel you're burning, no matter how fast, you're getting zero miles to the gallon. Rest assured, each little spurt of fuel into the cylinders is being measured and figured into the overall mpg.

    Again, not a bug, perfectly functioning. You're moving, slowly, but burning fuel...the computer can now calculate mileage based on your speed and the amount of fuel being consumed.
     
    #2 efusco, Dec 21, 2004
  3. daniel

    daniel Cat Lovers Against the Bomb

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    Addendom to what Evan said: When the engine is cold the system wants to avoid putting a load on it if possible, during the first minute or so. Thus it uses battery power. But you are burning fuel, and moving, so there's an mpg calculation, even though that fuel is not being used to move the car.

    Similarly, when you're in electric mode you have infinite mpg, because you are moving but burning no fuel, even though you will burn fuel later to recharge the battery. The MFD shows infinite mpg with the highest number it can display.

    The presence of the battery renders the instantaneous mpg reading very nearly useless. I'd like an ammeter, so I'd know the third leg of the triangle:

    1. How much gas is being burned.
    2. How hard the car is working.
    3. How much energy is being sent to the battery, or drawn from it.
     
    #3 daniel, Dec 22, 2004
  4. DanMan32

    DanMan32 Senior Member

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    What would be neat is to have numbers near the flow lines. I was just thinking that yesterday. There is enough room to put them there.

    Wish the MFD was Linux. Then we could customize and improve on it.
     
    #4 DanMan32, Dec 22, 2004
  5. efusco

    efusco Moderator Emeritus
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    Toyota needs to offer a package GP (aka the Geek Package)! It would include all the stuff in the BC, a fancier more informative MFD read-out ala the stuff in the Mini-scanner. Maybe an RPM guage and an engine/regen brake indicator.
     
    #5 efusco, Dec 22, 2004
  6. Ken Cooper

    Ken Cooper New Member

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    For what it's worth, over this past 16,000 miles of mixed condition driving on my 2004 Prius, I've experienced a good match between displayed and actual MPG. I find that doing rough round-off-the-numbers math (miles driven on the tank divided by displayed MPG) is really a better indicator than my gas gauge for when to gas up.
     
    #6 Ken Cooper, Dec 22, 2004
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