Prius Eco 58 MPG vs Prius 54 MPG - What's the difference?

Discussion in 'Gen 4 Prius Fuel Economy' started by cyclopathic, Nov 18, 2015.

  1. cyclopathic

    cyclopathic Senior Member

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    So why such big diff in MPG btw Two and Two ECO? it can't be just down to tire and LowE windshield. Just b/c of battery?

    EDIT: the title above reflects the City EPA rating, which isn't affected by aero improvements. The original question was posted to shed the light on how very similar weight-wise ECO could achieve 8% increase in CITY cycles. The hwy rating of Gen4 vs ECO are 50 vs 53 respectively.

    Below Tony's table with features:
     
    #1 cyclopathic, Nov 18, 2015
    Last edited: Nov 19, 2015
  2. Danny

    Danny Admin/Founder
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    Weight. 65 pounds of spare tire and battery.
     
  3. cyclopathic

    cyclopathic Senior Member

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  4. Danny

    Danny Admin/Founder
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    I'm just relaying what Toyota told me. Weight is the only difference that we were told (and the only one that I can think of).
    Edit: I forgot one more thing. The rear wiper has been removed. Guessing that saved weight and improved aero.

    I'm no engineer, so I just listen to the people who are.
     
    #4 Danny, Nov 18, 2015
    Last edited: Nov 18, 2015
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  5. cyclopathic

    cyclopathic Senior Member

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    I am an engineer, so forgive me for being skeptical.
     
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  6. Danny

    Danny Admin/Founder
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    I just added that I forgot about the rear wiper being removed from the Eco model. So perhaps aero improvements along with weight?
     
  7. cyclopathic

    cyclopathic Senior Member

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    Aero improvements should help with hwy MPG, but not much with city. I am guessing the battery and the programming to go alone with it.
     
  8. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Are the vanes universal?

    I found a complete lower bumper block gave a 3-4% improvement in highway MPG. I had mentioned it at Detriot to the chief engineer.

    Bob Wilson
     
  9. cyclopathic

    cyclopathic Senior Member

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    Reduced power output?
     
  10. Vman455

    Vman455 Senior Member

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    The press release reads, "A new Eco grade model is expecting ratings of 58 MPG city / 53 MPG highway / 56 MPG combined thanks to lighter weight and further optimized aerodynamics."

    I'd bet more has been done (aerodynamically) than just removing the rear wiper. Toyota claims a reduction for the Corolla LE Eco of Cd .02 (from .30 to .28) compared to the regular LE, even though the two models look the same, and improvement of +1mpg city/+4mpg highway/+3mpg combined with no improvement in weight. Aerodynamics play a role any time a bluff body moves through air, and reducing aerodynamic drag will improve efficiency at any speed--the effect becomes more pronounced at higher speeds.
     
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  11. spwolf

    spwolf Senior Member

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    it is weight that helps with the city... tires help with everything and aero at highway speeds.

    There is no power difference or anything like that, which is obviously from all the materials.
     
  12. Mendel Leisk

    Mendel Leisk Sand Pounder

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  13. cyclopathic

    cyclopathic Senior Member

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    Look at the post #3 and run numbers through ecomoddler calculator. There is absolutely no chance 65lbs saving on 3000lbs car would give improvement from 54 to 58 MPG















    Android merge. :)







    I buy for the highway but for city?? Aero would not mean much. Check with ecomoddler calculator, the difference at speeds under 25MPH is not 8%. Corolla ECO is bad comparison because it has CVT transmission and non-eco doesn't.
     
    #13 cyclopathic, Nov 18, 2015
    Last edited by a moderator: Nov 19, 2015
  14. bisco

    bisco cookie crumbler

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    will these numbers hold up on the epa test?
     
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  15. Jeff N

    Jeff N The answer is 0042

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    I don't understand the mpg difference between the regular and Eco trim either. It seems weird.

    Are the tires really the same size and height/width ratio on the Eco as the other 15" wheels. Different tire design?
     
    #15 Jeff N, Nov 18, 2015
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  16. giora

    giora Senior Member

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    It is ~8% (56/52). On JC08 it is also 8% (40 km/l vs. 37).
    What really seems weird to me is the low non Eco estimates on EPA! only 4% improvement from Gen 3 (JC08 and NEDC show considerably higher improvements.
     
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  17. JanoLietac

    JanoLietac Junior Member

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    It's not ~8%. The independent variable needs to be in the nominator.

    56mpg = 4.2L/100km
    52mpg = 4.5L/100km

    (4.5-4.2)/4.5 = 6.7%
     
  18. Jeff N

    Jeff N The answer is 0042

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    Yes. My vague impression is that JC08 and NEDC are slower speed and steadier whereas EPA cycles speed up and slow down more and have higher speed cycles.

    One obvious possibility is that the new powertrain has been especially optimized for certain speed ranges and steady speeds (mild torque) compared to gen 3.
     
    #18 Jeff N, Nov 18, 2015
    Last edited: Nov 18, 2015
  19. cyclopathic

    cyclopathic Senior Member

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    No surprise at all C/Aqua was rated considerably higher than Gen3 on JC08 and barely on par EPA. 4% means that the only real improvement is engine thermal efficiency, the rest of the car is on par with Gen3.
     
  20. giora

    giora Senior Member

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    It is a surprise to me.
    Unlike Gen 3 (non Eco), Aqua achieved artificially high score on JC08 due to their 'weight classes' system. If you compare it to Gen 3 Eco in Japan (also artificially high score of 32.6 km/l) you see about the same 'barely on par'.
    Here we are talking about two cars with almost the same weight and same 'weight class' on JC08.

    Wrong mathematics.
     
    #20 giora, Nov 18, 2015
    Last edited by a moderator: Nov 19, 2015
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