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Comparing Performance and Non-performance Ranges

Discussion in 'Model X' started by Jrogville, Apr 3, 2017.

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  1. Jrogville

    Jrogville Member

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    Why is there such a small range jump from the Model X P100D to the 100D (6 extra miles), compared to the Model S, which has an increased in range of of 20 miles from the P100D to the 100D?

    Or putting it another way, there's only a 9% increase in range from the Model X P100D to the Model S P100D (289 mile range to 315 miles), while there is an almost 14% increase in range from the Model X 100D to the Model S 100D (295 mile range to 335 miles).

    I had hoped for a better range bump when we got the non-performance 100D for the Model X.
     
  2. Tam

    Tam Active Member

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    I don't know but could it be because of weight?
     
  3. Jrogville

    Jrogville Member

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    Well, additional weight is why the Model S has more range, but the weight differential should be the same between the Performance S's and X's and the non-Performance S's and X's, so the increases in range should be fairly similar in scope between Performance and non-Performance, yet the difference is almost 50% higher with the non-performance verses the performance.
     
  4. dmd2005

    dmd2005 Member

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    Full range charges have been reported to be in the 302 to 304 miles for the X100D. My first full charge gave 488KM or 303 miles. Tesla hasn't updated their site yet or maybe they are trying to get rid of their 90kWh packs first.
     
  5. FlatSix911

    FlatSix911 918 Hybrid

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  6. Jrogville

    Jrogville Member

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  7. FlatSix911

    FlatSix911 918 Hybrid

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    As the title of the thread is Comparing Performance and Non-performance Ranges :cool:
     
  8. Jrogville

    Jrogville Member

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    But that's only between the performance and non-performance Model S. My question is about the difference between the Model S and the Model X
     
  9. flar

    flar Member

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    There are 2 axes of this comparison:

    - "non-P X vs S" ratio different from "P X vs S" ratio
    - "X P vs non-P" ratio different from "S P vs non-P" ratio

    I think the latter may be more telling as it indicates a different approach to adding performance capabilities? The only practical differences that I'm aware of on the X in going from non-P to P that is different from the way that the S goes from non-P to P would be that the X has a higher starting weight and that the X gains an active spoiler whereas the S does not.

    The reason that the higher base weight might be the differentiator is that electric vehicles start out at such a high efficiency that any factor that can hurt efficiency affects them more and then we combine that with a trick of mathematics. Basically because the weight has already de-optimized the efficiency of the X, another factor that also de-optimizes it has less of an impact. I see the opposite of this all the time in optimizing computer programs - when you have 3 or 4 modules that interact and all of them are inefficient then optimizing one of them has very little impact, but as you continue to optimize them then suddenly the last one you optimize has a comparatively larger impact on the overall performance. It's like a bunch of poles in a tent - remove one and the tent doesn't collapse much - remove all but one and the tent is still mostly standing - remove the last one and the tent collapses. So, a heavier vehicle with a larger frontal area isn't as affected by the P motor being less efficient.

    Another reason weight might be a factor is that the smaller motors may already be outside of their optimum efficiency trying to move the higher weight and so moving to an even more powerful motor actually balances "better suited for the given weight" against "not as naturally efficient as the smaller motor" and cancels some of the loss out.

    The active spoiler may also eliminate some of the range loss, but I don't think we have any data to support that other than vague marketing claims from the past. Perhaps a number of people with early non-P X's that had the active spoiler before they developed the fixed spoiler could compare their range performance against similar configs after the fixed spoiler started being delivered?
     
  10. Jrogville

    Jrogville Member

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    Under what conditions does the spoiler help? And under what conditions does the active spoiler help more?

    Also, your discussion about performance vs non-performance motors brought a question to mind. Is it possible that in order to maximize production efficiency, Tesla used the same motors in the non-performance models as in the performance Model X's, since less X's are built than Model S's? And therefore loosing the range extension you would get from putting in motors optimized for energy consumption rather than performance? They could then software limit the performance of the non-P 100D's. Do we know that there are indeed different motors in the 100D's from the P100D X's?
     
  11. flar

    flar Member

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    I was merely saying that it is a factor that represents a difference between the upgrades in the S vs the X and its intent was to improve efficiency (and handling per their claims, but that wouldn't be germane to a range discussion). I looked up the text on the Model X order page and they claim a 1.6% improvement in efficiency in highway driving range for the active spoiler.

    So, the performance Model X gains an item that is alleged to improve aerodynamic efficiency that the non-performance Model X doesn't have.

    The performance Model S has the same aerodynamics as the non-performance Model S.

    That is one factor that could cause the 2 ranges in the Model X to be closer to each other as compared to the 2 ranges in the Model S. The range difference in the Model S is dominated by the change in the motors. The range difference in the Model X is also affected by the change in the motors, but it is also potentially offset by the presence of an aerodynamic aid.
     
  12. Jrogville

    Jrogville Member

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    I was just curious about the spoiler generally. Didn't know anything about them. I guess they help at highway speeds? Why make them retractable? Does it become detrimental at low speeds, or is it just a case of it looking nicer when it's retracted, since it's not going to help you at low speeds or when stopped?
     
  13. flar

    flar Member

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    Ah, general info on spoilers. There is a pointer to a nice youtube video that goes over spoilers around here somewhere, but basically the issue is that while the front of the car may be relatively sharp and smooth to displace the air with little fuss, the back of the car is basically just a giant vertical wall and the smooth flowing air coming over the rear surfaces has to make a sudden and sharp turn to fill that gap. The spoiler takes the trailing edge of the smooth air flowing over the bodywork and "spoils" its smooth flow, causing turbulence, which is able to fill in the void behind the car more easily than a jet of smooth flowing air. This reduces the low pressure following the back of the trunk and thus reduces that aerodynamic drag. At different speeds, different spoiler angles will direct turbulence in different directions and so what might produce adequate turbulence at one speed may not help the area directly behind the car at other speeds, and vice versa. So, adjusting the angle makes sure that the spoiler continues to do its job under a wide variety of conditions:

    Spoiler (car) - Wikipedia

    (I found the video I saw posted earlier and I decided not to include the link because it seems to confuse the aerodynamic role of preventing the low pressure behind a car with a downforce effect - downforce is a different animal and can help prevent rear wheels from losing traction at high speeds, but it isn't so much of a range issue compared to eliminating the low pressure behind a car that creates drag and reduces range...)
     
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  14. Jrogville

    Jrogville Member

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    Thanks for the info, @flar! So does the retractable Tesla spoiler adjust with speed as well, or is it a binary "up-down" type behavior?
     
  15. goneskiian

    goneskiian Active Member

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    The Model S also has an available spoiler option. The carbon fiber one that is available only on the P models. They don't say it improves range but aerodynamics tells us it should. Maybe not enough for them to advertise it like the X though.

    The X's adjustable spoiler has 3 positions. All the way down when it's parked and locked. All the way up in the high visibility setting which is pretty much parallel to the ground and maximizes rearward visibility by allowing you to see under it. This is the position it takes when the vehicle is on and moving under about 50mph. At 50 it moves down slightly to maximize aerodynamics at highway speeds.
     
  16. goneskiian

    goneskiian Active Member

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    #16 goneskiian, Apr 5, 2017
    Last edited: Apr 5, 2017
    Except that the "spoiler" on the X is actually an airfoil so it can actually do both. Especially if it can change it's angle...

    Sports Car Aerodynamics: Spoiler Alert! - YouTube
     
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  17. Jrogville

    Jrogville Member

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    Thanks for this info as well, @goneskiian. I won't have a practical need for this knowledge since my X will have a fixed spoiler, but it's fun to know about it anyway.
     
  18. flar

    flar Member

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    What evidence is there that the spoiler on the X is an airfoil? The video touts the advantages of both, but it doesn't really give any defining characteristics other than the airfoil they show is more of an inverted wing with an upward sweep and the spoiler on the X is very flat and never goes more than horizontal.

    I have a number of issues with that video in that it is all about downforce and racing where downforce matters due to improving acceleration at speed and improving cornering. Neither of those matter for range. The range-improving action of a spoiler is to reduce the low pressure behind the car and they don't really focus on that aspect.
     
  19. goneskiian

    goneskiian Active Member

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    Good question. I based my statement on the video's description that an airfoil allows air to pass underneath it while a spoiler does not.

    And this article proves how little I actually know...

    http://oppositelock.kinja.com/wings-spoilers-youre-probably-doing-it-wrong-1665312667

    So, I'm wrong in calling it an airfoil. It's still a spoiler.

    I will include this bit from it though...

    "By preventing airflow from entering a region with an unfavorable body shape, the flow streams around the entire vehicle can be improved. Laminar airflow will avoid the obstruction, modifying the effective body shape, so a properly-designed spoiler can improve the drag coefficient of the vehicle even though it looks like a wall. That reduces drag and improves efficiency."
     
  20. flar

    flar Member

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    There are a lot of reference articles out there and many of them seem to conflict. I started with Wikipedia, which can have its own drawbacks, but what they said made a little more sense to me:

    Spoiler (car) - Wikipedia

    One thing in particular, is that they seem to define it not by where the air goes or its shape, but what function it has. A spoiler is simply disrupting an undesireable air flow. Other articles show spoilers as not having air flow under them and define it that way, but you can have a wing-like shape that changes how the flow behaves at the rear of a car without specifically generating aerodynamic down force like an inverted airplane wing so I like the way that the Wikipedia article approaches it. Also Tesla and many car manufacturers call small flat wing-like structures on the rear "spoilers". Most of the articles talk about wings and distinctly show them turned up and shaped much like an airplane wing (curved with a longer surface path on the side you want to press towards).

    Definitely a bump on a trailing edge like the Model S spoiler is clearly in the spoiler realm as are the mostly vertical walls on the back of NASCAR vehicles.

    And upward turned shapes that have a cross section like an upside down airplane wing are clearly trying to create un-lift to improve down-force.

    The rear spoiler on the Model X doesn't seem to fit squarely into either category. I could see it being called an airfoil because it has the air on both sides, but it isn't shaped in the best way to push down - it's more like putting your hand out the car window and playing with the flowing air than an airplane wing.
     

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