TMC is an independent, primarily volunteer organization that relies on ad revenue to cover its operating costs. Please consider whitelisting TMC on your ad blocker or making a Paypal contribution here: paypal.me/SupportTMC

What if? ( upgrade package )

Discussion in 'Roadster' started by richkae, Oct 29, 2011.

  1. richkae

    richkae VIN587

    Joined:
    Jan 15, 2008
    Messages:
    1,917
    #1 richkae, Oct 29, 2011
    Last edited: Oct 29, 2011
    Suppose Tesla offered an upgrade package for your Roadster:
    90kWhr battery ( top of the line cells like the Model S Sport )
    SuperSport PEM paired with SuperSport motor. ( technology from the Model S Sport )

    Pricetag: $35k ( really $50k, but they give you $15k credit on tradein of old parts, you could probably sell your old battery+PEM+motor for more )

    What you get ( upgrading from non-Sport Roadster ):
    390 mile range instead of 245
    420hp instead of 288hp
    0-60 of 3.1 seconds instead of 3.9
    1/4 mile time of 11.2 seconds instead of 12.9

    Would anyone bite?
     
  2. TEG

    TEG TMC Moderator

    Joined:
    Aug 20, 2006
    Messages:
    17,249
    Location:
    Silicon Valley
    You would probably want a brake upgrade to go along with that!
     
  3. Norbert

    Norbert TSLA will win

    Joined:
    Oct 12, 2009
    Messages:
    4,424
    Location:
    San Francisco, CA
    Had this in mind already... as long as the Model S (sport) power train can be made to fit in the Roadster, this would be a great way to handle the battery-end-of-life situation for Roadsters already sold (though currently development resources might be very busy).
     
  4. I would 100% pre-pay for this and upgrade immediately, this would mean that people from so cal could make a trip to nor cal without a charge I would do this in a heart beat sign me up!! no more range anxiety!!!!!
     
  5. W.Petefish

    W.Petefish Active Member

    Joined:
    Apr 29, 2011
    Messages:
    1,059
    Location:
    North Texas (DFW)
    I would speculate that the battery contract that was offered with the purchase of the roadster would have to come into play. So that'd be $12k subtracted from that price.

    I'd say worth the extra cash.
     
  6. richkae

    richkae VIN587

    Joined:
    Jan 15, 2008
    Messages:
    1,917
    Would you want the whole package ( motor+PEM ) that gives the performance upgrade?
    Or just the battery for the range upgrade?
     
  7. PV4EV

    PV4EV Member

    Joined:
    Oct 26, 2011
    Messages:
    477
    Location:
    Area 51 / UK
    I think the majority of owners would be interested in just a higher capacity ESS rather than the whole PEM/Motor/ESS.

    But I'd like to know if the existing PEM and motor could handle, say, a 20% increase in current delivery, in which case it might be possible to have marginally better torque / acceleration. I am not sure a redesign of the ESS for an increase in voltage would be that worthwhile as this would translate into higher top speed which is fairly academic.
     
  8. richkae

    richkae VIN587

    Joined:
    Jan 15, 2008
    Messages:
    1,917
    The Roadster Sport PEM+motor handles 20% more current than the Roadster. I dont think there is a lot of headroom in either for more than they currently do.
     
  9. vfx

    vfx Well-Known Member

    Joined:
    Aug 18, 2006
    Messages:
    14,792
    Location:
    CA CA
    Plus one.

    I wonder about were the weight would go. The Roadster has always been a heavy car. Adding in a bigger powertrain (and brakes) is now straining the tub and handling would have to be dealt with. It's a delicate balance setting up a great car and just putting in another XXX horsepower does not equate a wholly superior car.


    Add lightness!
     
  10. Alan

    Alan Member

    Joined:
    Sep 18, 2010
    Messages:
    248
    Location:
    UK
    I am not interested in a higher capacity ESS, but would pay for a lighter battery pack of the same capacity using new technology cells.

    Less weight will give better handling, braking, acceleration and range.
     
  11. bonnie

    bonnie Oil is for sissies.

    Joined:
    Feb 6, 2011
    Messages:
    14,241
    Location:
    Columbia River Gorge
    I'd go for the added range from decreased weight, better battery technology, and/or more batteries. Bring it! (Would be great to take road trips with just one charge stop/day, plus overnight.)
     
  12. Norbert

    Norbert TSLA will win

    Joined:
    Oct 12, 2009
    Messages:
    4,424
    Location:
    San Francisco, CA
    Reducing the battery weight might more than offset any additional weight from the Model S power train. At first I thought that might make it easier for Tesla, but now I am not so sure anymore. For example, due to liquid cooling of the motor, it may also require a new cooling system.
     
  13. Eberhard

    Eberhard #421 Model S #S32

    Joined:
    Oct 17, 2010
    Messages:
    1,141
    Location:
    Germany
    #13 Eberhard, Oct 30, 2011
    Last edited: Oct 30, 2011

    please add 3-ph charger (22 or 44kW) and i will buy.

    longer range not really needed, because the speed of charging is limiting the speed of travel.
    Therefore, fast DC-Charging would be important as well-
     
  14. PV4EV

    PV4EV Member

    Joined:
    Oct 26, 2011
    Messages:
    477
    Location:
    Area 51 / UK



    Two years ago I went into a lot engineering investigation and mathematical modelling when planning to adapt a modern production car into a pure EV. I've still got the rather attractive 4WD Italian sports car that I bought for the purpose, which is all very nice, but it drinks £4,000 of petrol every year at present and costs way to much to run. It’s a long story why I opted for a Tesla in the end though..!

    It was an interesting exercise that sharpened a lot of lost knowledge from university days. The modelling for efficiency / energy usage included many factors such as mass, Cd, Ca, air density, rolling resistance on tarmac and concrete, transmission losses and so on. Below I summarise some interesting overall points regarding what can be done to any car to improve various aspects like better range, better acceleration or better overall efficiency.

    (I appreciate that there may well be far wiser people on the forum than I, but others might find this useful. One other caveat - I am sure Tesla Inc spent millions optimising the car, within reason … )


    Broadly speaking, there are two factors that drain energy to keep a car moving at freeway speeds, one is rolling resistance, the other is air resistance.

    As the speed of the vehicle increases the rolling resistance increases linearly, where as the air resistance increases exponentially.

    At above 50+ mph, air resistance becomes increasingly dominant factor. At 100mph air resistance accounts for about 80% of the energy goes into pushing the car forwards.

    Big reductions in weight will marginally reduce losses through rolling resistance and improve acceleration, but will not effect losses due to air resistance.

    Whereas marginally reducing the coefficient of drag and frontal area (Cd, Ca) significantly improves losses due to air resistance.



    Using a freeway speed of 70mph and plugging it into some of those spreadsheets, I can pull out some statistics as follows :-

    Loosely speaking, a -20% weight reduction on a Tesla ( = - 250kg !) would improve Wh/Mile efficiency by only about 7%. If this were somehow more dramatic at, say, -40% reduction then still the efficiency improvement is only 15%. So major weight savings would be prohibitively expensive without considering some equally major changes to how the car is made, although the future is looking interesting for this.

    However, reducing the Roadsters Cd from 0.35 down to a more reasonable 0.30 would improve the Wh/Mile efficiency by 9-10% straight off, and getting it down to 0.25 would make it nearly 20% better. ( Its worth noting that the Cd for the Model 'S' is apparently 0.27 which is very good compared to almost every other similarly sized car)



    So, efficiency benefits through weight savings alone are going to be very difficult. But there's quite a few practical things that can be done that if used simultaneously can improve energy efficiency at speed way more than trying to shed 250kg of weight ! For example :-

    - there are tyres becoming available which have almost half the rolling resistance of conventional tyres which will improve the 70mph Wh / Mile efficiency by up to 15% straight off. But to use these will mean some marginal compromises in areas like ultimate grip, road noise and so on.

    - pumping your tyres up by 5-10psi will have a worthwhile effect on rolling resistance to the tune of 3-4% of efficiency

    - replacing the wing mirrors with bullet cams and small OLED screens on the inside would improve Cd and Ca giving about 3 to 3.5% efficiency benefit.

    - if you want range, drive with the hard top on. The Cd goes up considerably with it off.

    - You can improve steering responsiveness, acceleration and some weight effects by using lightweight alloys and tyres, often reducing the unsprung mass by 25kg-30kg. When moving at speed this would have a similar effect to reducing mass of the car by 5% giving about a 2% efficiency saving.

    - If you want 4% better acceleration whilst sacrificing top speed, you could reduce the rear wheel size from 17" to 16" but you'd run out of puff a bit quicker. (not actually sure if rear wheel discs/brakes allow this)

    - .. I am sure there's loads more.

    - … and finally, in my case, going on a diet and eating less doughnuts might save a % or two :biggrin: and make it less of a hernia inducing exercise getting in/out of the Roadster with the lid on !


    I've deliberately not touched on other aero dynamic areas of how air flows around/over/under and exits at the rear, as this is way to complex to go into here. These would include the combined effects of flat undertrays, front splitters and lower spoilers, rear wheel covers, wheel spats, rear venturi's, kamm tails, vortex generators etc etc
     
  15. vfx

    vfx Well-Known Member

    Joined:
    Aug 18, 2006
    Messages:
    14,792
    Location:
    CA CA
    An engineer said the S will have a better CD than any car for sale now by far.
     
  16. Norbert

    Norbert TSLA will win

    Joined:
    Oct 12, 2009
    Messages:
    4,424
    Location:
    San Francisco, CA
    That might (or might not) include any recent improvements in the CD value since that number was calculated.
     
  17. PopSmith

    PopSmith Saving for a Model 3

    Joined:
    Jan 22, 2010
    Messages:
    608
    Location:
    Utah
    #17 PopSmith, Oct 30, 2011
    Last edited: Nov 1, 2011
    If the Model S (Alpha?) had a Cd of 0.27 I could see the Model S beating the Cd of any consumer-level car for sale in 2012. While definitely not an exhaustive list the Wikipedia article says the 2012 GT-R and Mercedes-Benz B-Class (with "Eco-package") are the only 2012 production cars with better Cd at 0.26. It would be awesome if the production Model S Cd ends up being 0.24 or lower.
     
  18. Alan

    Alan Member

    Joined:
    Sep 18, 2010
    Messages:
    248
    Location:
    UK
    Thanks for the above post - lots to think about. Personally though I spend very little time at 70mph. Looking at the logs most of my driving is accelerating (hard) from 20 to 60 and braking back down again as I drive through the twisty country lanes locally. Other than that I am usually stuck at 40mph on main roads behind other traffic. Freeway / motorway driving at 70mph makes up a small part of my driving.

    With the way I use my car I assume a 20% weight saving would have a much bigger effect on range than the 7% mentioned.
     
  19. bolosky

    bolosky Member

    Joined:
    May 5, 2009
    Messages:
    422
    Are you sure? I think that air resistance goes up cubically with speed, not exponentially. That's a *big* difference.
     
  20. VolkerP

    VolkerP EU Model S P-37

    Joined:
    Jul 6, 2011
    Messages:
    2,455
    Location:
    Germany
    #20 VolkerP, Oct 31, 2011
    Last edited: Oct 31, 2011
    In my text book aerodynamic drag depends on speed to the power of 3. Calling it an exponential increase is not correct, but it gives many folks a familiar concept of "growing not linear, but waaaay steeper".

    Edit: appropriate post here: Roadster Efficiency and Range

    The Model S Cd was mentioned by Elon to be 0.225 which would be an excellent value.
     

Share This Page