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Model 3 Specification Speculation

Discussion in 'Model 3' started by omgwtfbyobbq, May 7, 2016.

  1. omgwtfbyobbq

    omgwtfbyobbq Member

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    Since it's fun to speculate, I threw together a little python script that uses the EPA FTP-75/HWFET traces and the unadjusted EPA rating of the S 70D to guess at Model 3 range. Using an admittedly crude comparison, I'm guesstimating a 55kWh 3 will hit 240+ mile combined and 75kWh 3 will hit 325+ miles combined with a .21 Cd. A .24 Cd hits 220+ miles for the 55 and 300+ miles for the 75.

    Here's a link to my script. I appreciate any suggestions and constructive criticisms.

    Model3.py

    In terms of the nuts and bolts, I assumed the 3 would be 71" wide and 55" tall with a drag coefficient of .21/.24. The estimated dimensions are from the Model 3 dimensions thread on this forum. The 55s weight is estimated to be 1815kg with a driver and the 75 weighs 1905kg with a driver. That estimate is assuming a 20% smaller vehicle with a little more steel, which I adjusted for by comparing the curb weights of the last gen high strength steel F150 to the current Al bodied F150, and the increase in battery weight is form the current differences in the weight of a 70D/90D. The Crr is .0089, which is from a 2014 Tesla blog post on the Roadster 3.0. The S 70D specs I found on the interweboftubes.

    Long story short, the script grabs the EPA trace files from the site, and for each data file, loops through each entry and sums the power required to overcome aero and rolling drag for each car. The range estimate is pretty straightforward. It's just the product of the ratio of S 70D power to Model 3 XXkWh power, the ratio of battery capacities, and the 70D 5-cycle range.

    This I think provides a good physical ballpark, but like most things could be improved. One of the assumptions I made is that the 3's baseline power consumption would scale with the car's size compared to the S, but that might not be accurate. I've seen 50W used for the roadster, so if someone could dig up the figure for the S 70D, they could use that to get an accurate idea of what lesser (or no) improvements to that figure would do to range. Someone who is better versed with Al/HSS vehicle construction could probably come up with more accurate weight/area estimates.

    The EPA only publishes the Wh/mile figures for the FTP75/HWFET tests, so if we could get the S 70D's figures for the other 3 tests as well as the method used to derive the adjusted 5-cycle range from all 5 tests, that would help out a bunch. There's also the trade-off between motor gearing/efficiency and 0-60 times, which I think the current 90D takes advantage of to get better highway range than the 70D, even though it weighs a few hundred pounds more.

    Nailing down all those relationships would I think provide a nice view of how the Model 3 will perform.
     
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  2. igotzzoom

    igotzzoom Member

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    I'm just hoping I can get 0-60 in 4-4.5 sec for around $42k. I know I originally said I'd be happy with a 6-sec 0-60, but the sneak preview has me hoping for more. :cool:
     
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  3. geoffreak

    geoffreak Model 3 Reservation Holder

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    Here's a version of the script viewable online.

    Your calculations seem to line up with Elon's statement of at least 215 miles. I don't think he would have said at least 215 unless he thought there was a high possibility of surpassing that by a significant amount. 240 miles seems to be right around this window.

    I want to see what you get for a few different battery sizes (± 5-10 kWh).
     
  4. SageBrush

    SageBrush Active Member

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    VERY spiffy!

    I don't have any experience with python, but I tried anyway ...
    I downloaded the script and tried to run it in a free python editor available for the Chromebook.
    It seemed to load OK but running the script caused this error

    Screenshot 2016-05-07 at 3.56.32 PM.png
     
  5. Johan

    Johan Took a TSLA bear test. Came back negative.

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    Tires. A lot can be done with tires and wheel dimensions. The Model 3 isn't Model S or X so it won't come with those kinds of big wheels.
     
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  6. Jeff N

    Jeff N Active Member

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    Not that I think it will make a huge difference, but it's worth remembering that Elon did not claim that the Model 3 Cd is .21. He said that they were trying for .21 but implied that they weren't quite there yet and were still tweaking the design with .21 as a target.
     
  7. Jayc

    Jayc Member

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    Don't know whether that is a valid statement in this context where tyre grip matters for performance, we may be a bit constrained.
     
  8. RobStark

    RobStark Active Member

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    Model 3 isn't a Prius Eco either. It won't come with tiny narrow LRR tires.
     
  9. Johan

    Johan Took a TSLA bear test. Came back negative.

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    I agree it won't come with very narrow tires but I'll gladly bet you it will come standard with a LRR tire.
     
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  10. el crucero

    el crucero Member

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    It depends on how you define "narrow." I have LRR tires on my plug-in Prius and they are not narrow but I still get 70 to 75 mpg.
     
  11. SageBrush

    SageBrush Active Member

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    Roadster 3.0 is spec'd with 0.0089 kg/ton CRR tyres. I think we can consider that a conservative upper bound. Honestly though, it just seems common sense to offer a fuel economy choice and a 'beat the other car to the next red light' choice.
     
  12. omgwtfbyobbq

    omgwtfbyobbq Member

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    Which editor are you using?
     
  13. SageBrush

    SageBrush Active Member

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    Python Editor 5.1.0

    It is a Chrome extension, running on a Chromebook
     
  14. Topher

    Topher Energy Curmudgeon

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    If they are at the level of tweaking 0.1mm, they are nearer 0.22 (in a quest for 0.21) than 0.24. IMHO.

    Thank you kindly.
     
  15. omgwtfbyobbq

    omgwtfbyobbq Member

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    I tried running it on my chromebook, but there's an *issue with I think jquery that's getting in the way of urllib.

    The Python interactive shell appears to be more functional, I'll take a look at it later this week and upload whatever I can get working.

    * NetworkError: Failed to execute 'send' on 'XMLHttpRequest'
     
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  16. kzod

    kzod Member

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    He could put on wagon wheels like the BMW i3.
     
  17. jeffhre

    jeffhre Member

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    "The 55s weight is estimated to be 1815kg with a driver and the 75 weighs 1905kg with a driver..."

    The 55s weight is estimated to be 1815kg (without) a driver and the 75 weighs 1905kg with a driver.
     
  18. omgwtfbyobbq

    omgwtfbyobbq Member

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    #18 omgwtfbyobbq, May 14, 2016
    Last edited: May 14, 2016
    According to the Motor Trend estimates the 55D will weight 1973kg without the driver and have a frontal area that's ~1.075 times my estimate (74.2" x 56.5" instead of 71" x 55"). On the flip side, if Jeff's right, Cd is likely .21-.22, which sounds right. Feel free to plug and chug to check what the different numbers do to range.
     
  19. SageBrush

    SageBrush Active Member

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    My son says "plug and chug."
    Freud would be amused
     
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  20. omgwtfbyobbq

    omgwtfbyobbq Member

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    Haha, autocorrect for the win, or lose. The Motor Trend weight figures are kind of weird though. Using their estimate for the 75D, the curb weight + driver is ~2150kg, which is within 3% of a Model S 70D. Granted, an extra ~20+kg is from the extra 5kWh of batteries, but that still seems a bit high.

    I think they're using the Model 3 width with mirrors out, which I shouldn't use for the CdA calculation. If they are using the mirrors out width, then the actual area should be just a hair above my estimate, or maybe the same since without the mirrors their estimate could be a inch thinner even if it's also an inch taller
     

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