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Will Model 3 have a 0.20 drag coefficient?

Discussion in 'Tech Talk' started by ratsbew, Jul 15, 2017.

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  1. ratsbew

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    Elon Musk was aiming for a 0.21 drag coefficient for Model 3 (Model S is 0.24). A coefficient of drag that low coupled with the somewhat smaller proportions of the Model 3 over the S will lead to very good highway speed range.

    Do we have any updated information of how slippery the Model 3 will be and what kind of Wh/mile can be expected at highway speeds?
     
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    • SoFlaModel3

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      I am hopeful we will get that information on the 28th!
       
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      • Cloxxki

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        Well, there was that sneaky picture of a (likely ~75kWh) Model 3 charging which seemed to imply an EPA rated range of up to 308 miles or so accordin to some of the pixel counters. That's 243Wh/km. The 60 would be slightly, slightly less than that due to having a ~70-90kg extra in battery weight. D versions may end up being slightly more economical still due in line with what we've see with non-P Model S&X.

        Likely the Model 3 will NOT be a light car, not compared to I3 and even Bolt.
        It could end up just about the weight of a Model S, having been built with cost as only to safety in the priorities. And the size difference is tine. Same height, while width*lenght comes to -10% only.
        For a heavy car, the city consumption I believe tends to suffer more. With so much effort on aero for Model 3, the highspeed consumption is bound to be significantly better than city, whereas for the Chevrolet Bolt, it's actually the other way around. Light car, boxy design. Rules the city (there are others that do with fewer electrons), but is so-so at speed. Will use A LOT at 75+mph.

        For highway speeds, type of motor, gearing (to hit efficiency sweet spot) but foremost frontal surface area and drag coefficient are key factors to actual Wh/mi economy. With the frontal surface just 4% less if you look at specs (width), the slickness will have to make the most of the diffference.
        Model S is pretty awesome at modest highway speeds.
        Reference:

        Just under 50mph (cruising 80km over somewhat hilly terrain), 136Wh/km = 219Wh/km.
        I'd expect Model 3 to manage sub 200Wh/km on that particular drive, at least the D version. The first car to be built, 3-75 or whatever it will be called, is not going to be the best in terms of economy. 60 is lighter, D likely more economical.

        Great reference: http://insideevs.com/detailed-look-...ange-rating-for-all-versions-of-2016-model-s/
        S75 non-D gets 252.7mi of highway range. If we take the 72.6kWh usable, that's 287Wh/mi, 178Wh/mi.
        The first Model 3 is expected to be the little bother of this one, RWD, similar 75kWh capacity. Expect Model 3 to do relatively well at higher speeds.

        But remains guessing.
        In any case, we can expect to get further on the same nominal charge.
        While no-one wants to waste electrons, many will carrre a lot about how quickly charging goes. With super quick charging, doing some mid drive doesn't hurt as much.

        Two things.
        First, I doubt Tesla are messing with aero wheels just for fun. Wouldn't be surprised if EPA data would be based on those. OnModel S, the now rare aero wheels seemed to work a treat.
        Second, once traffic laws allow it, might we see mirrorless cars (using cams and screens) be offered? There's one add-on screen in the car already, what's two more to ask as virtual mirrors?
         
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        • ratsbew

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          Going mirrorless is something I'm really looking forward to. I'm almost wanting to hold off on my Model 3 until I can get one without mirrors.
           
        • NRG4All

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          With our Nissan LEAF we were able to get about 4 miles/kWh. The battery was 24 kWh but the user did not have the use of the entire battery so we could consistently get 80 miles on a charge. I expect that the Model 3 should have a lower CD than the LEAF. Perhaps someone out there knows the CD of the LEAF. Thus, if a user can get 4 miles/kWh and have access to 70 of the 75 kWh's in the Model 3, that should equate to about 270 miles on a charge. Whoopee!
           
        • Cloxxki

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          The pic of a car charging seemed to imply 300+ miles. Could haven been a 3-75D.
           
        • Topher

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          I expect them the very second that laws allow it...

          2010 Leaf is rated at 0.29 Cd. If the Model 3 hits 0.21, that is 38% better (lower power requirement). Perhaps 40 more miles of range at high speeds for a 60kWh battery (all things other than Cd being equal).

          Thank you kindly.
           
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          • Cloxxki

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            Of course the rolling resistance of the heavier Model 3 may end up higher than the 2010 Leaf, but there is room for gains for sure. The higher the speed, the less of a factor rolling resistance is, as it just goes up proportionately with speed whereas air drag increases roughly by the third power. Twice the speed -> 2³ = 8x the air drag. A 200kph car can suffice with around 100hp, a 400kph car tends to take 700+hp.
             
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