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3LR (RWD) vs.P3D Efficiency Comparo (Imperfect)

Discussion in 'Model 3' started by ForeverFree, Aug 22, 2018.

  1. ForeverFree

    ForeverFree Supporting Member

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    #1 ForeverFree, Aug 22, 2018
    Last edited by a moderator: Aug 25, 2018
    Last weekend, opportunity presented itself.

    Both my wife and I would be doing the same drive at the same time. She, in her 3LR, me in my P3D.

    So, I arranged to follow her and match speed (helped by AP).

    The experiment was not perfectly controlled:

    As the tail car, the P3D benefitted from steady-state drafting (3 notch TACC following distance). The lead car was able to maintain this same distance behind other traffic most of the way, but not at all times. Net benefit (slight) to P3D.

    The route was moderately uphill (+900 feet). Net benefit (slight) to 3LR (lighter weight).
    Nevertheless, I figured that folks might be interested in the results, even if flawed.

    So, for fifty uphill miles, most, but not all, on freeway at 72-74 mph, reported consumption was:

    3LR -- 268 Wh/mi
    P3D -- 281 Wh/mi
    Difference = Roughly 5%
     
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  2. SoCalGuy

    SoCalGuy Active Member

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    #2 SoCalGuy, Aug 22, 2018
    Last edited: Aug 22, 2018
    I thought you had the P3D and a RWD? Did you mean RWD instead of "3D"?

    3D and P3D are same weight.
     
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  3. ebmcs03

    ebmcs03 Active Member

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    What?!??!? You have two Dual Motor model 3s already? Wow!
     
  4. Zoomit

    Zoomit Member

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    This is meaningless without defining which wheels/tires each car is using.
     
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  5. NewTMSMan

    NewTMSMan Member

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    Well P3D at about 280 Whr/mile is slightly less efficient than I was hoping. On a recent 800 mile highway trip maintaining similar speeds my Model S P100D averaged 243 Whr/mile, so the P3D will only be 15% more efficient than my P100D, was hoping it would be more like 25% better. That means, while I would get about 300 mile range in my P100D, now I can only expect about 268 miles range when we get our P3D.
     
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  6. SageBrush

    SageBrush 2018: Drain the Sewer

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    How much net elevation ?
     
  7. Zoomit

    Zoomit Member

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    I’m going to say 900 ft. ;)
     
  8. PhaseWhite

    PhaseWhite Member

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    Thanks for posting. Could you give more details on the the wheel conf of both cars?
     
  9. ForeverFree

    ForeverFree Supporting Member

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    Yikes; sorry!

    Yes, P3D and 3LR.
     
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  10. ForeverFree

    ForeverFree Supporting Member

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    Same.

    18 aero. Uncapped. OEM Michelin Primacy.
     
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  11. ForeverFree

    ForeverFree Supporting Member

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    Remember, that was uphill.

    Going in the other direction that day, I was under 240.

    Also, putting aero caps on would drop things another 5-10.
     
  12. Jedi2155

    Jedi2155 Model 3 has Arrived.

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    You should run the test again (and edit your original post/title with the correct details) with the Aero covers because its already been confirmed that the Aero covers provide ~5% improvement. If I take your 281 * .95 = 267 Wh/mi so if she was running Aero, it would match exactly.

    I would suspect the Wh/mi would be exactly the same
     
  13. ℬête Noire

    ℬête Noire Active Member

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    #13 ℬête Noire, Aug 24, 2018
    Last edited: Aug 24, 2018
    We can pull out the energy for the elevation rise:

    105kg * 9.8m/s^2 * 275m = 283kJ = 79Wh

    Assuming 50 mi the total difference between the two vehicles was 650Wh, so the rise only accounts for about 12% of the difference, but it makes the difference between the two vehicles [for a round trip or otherwise net zero elevation change] a lot closer to 4%. Nice, I'd resigned myself to lose at least 15 miles off full highway range and this is slightly below that (w/the caveat that you have to watch on uphill trips).

    No idea how to calculate to compensate for the "drafting" part of it, or how much that would affect the results.
     
  14. apacheguy

    apacheguy S Sig #255

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    My understanding of his response is that the RWD was running the same wheel config with uncapped Aeros. Apples to apples
     
  15. ForeverFree

    ForeverFree Supporting Member

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    Correct. No aero caps on either vehicle.

    Won’t have the chance to repeat or improve this experiment any time soon. So, just offering up it’s imperfect results as one more data point in our quest to ascertain D models’ real-world efficiency/range penalty.

    That penalty is real, but I believe that, in highway use, it’s smaller than the 8% hit shown in EPA testing.

    Eager for more data points from others1
     
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  16. SoCalGuy

    SoCalGuy Active Member

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    Mods: can you edit the thread's title to reflect this is a RWD comparison.
     
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  17. RyanT

    RyanT Member

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    #17 RyanT, Aug 24, 2018
    Last edited: Aug 24, 2018
    Great post! I suppose the LR had slightly more wear on the tires too? I think the Wh/mi comes down after the first 1-5k miles as the newness comes off the tires.
     
  18. Thomas Edison

    Thomas Edison Active Member

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    I just reported your post.
     
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  19. LargeHamCollider

    LargeHamCollider Battery cells != scalable

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    Need to make sure tire pressures are the same as well.
     
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  20. Jedi2155

    Jedi2155 Model 3 has Arrived.

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    It would also be helpful if Forever could update his original post to change references from 3D to 3LR or RWD. Would prevent confusion from the first post onward!
     

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