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Re-gearing? trade top speed for acceleration

Discussion in 'Roadster: Performance' started by rgjones, Aug 30, 2013.

  1. rgjones

    rgjones Member

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    Would like to start a discussion about the feasibility and possible trade offs if we were to change the gearing (final drive) on the Roadster.
    I still love my 2010 2.0 Sport but am ready for more acceleration!
    As it is I have my Tattler set to automatically select Performance mode when driving - never know when you might 'need it :)
    Most of the performance cars in my neighborhood slink off now, but saw an Aventador the other day! - Could be a challenge if he has time to engage launch control.
    So far it does not look like a lighter, lower (CofG) battery pack is going to happen soon (wish - acceleration & better handling),
    so it seems the simplest way to accelerate faster is to re-gear the car, trading off top speed.
    I'm ready to take top speed down from 125 to say 95.
    What would that do to the acceleration?
    Other factors to consider? WHr/mile changes at low load steady speeds? (70, 50)
     
  2. Doug_G

    Doug_G Lead Moderator

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    I did a charity drag race event recently. An Aventador took the top spot with a 1/4 mile time of 10.39. Both the Roadster and the Model S are in the 12 second range. Somehow I think it would be hard to catch him even without launch mode!

    Changing gearing like that might improve torque by as much as 30%. That certainly could make a significant difference. But I wonder if the firmware would freak out if you changed the ratio.
     
  3. hcsharp

    hcsharp Active Member

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    While you're at it, if we can change to a limited slip differential I would like that. A ltd slip diff would reduce range slightly and increase understeer but would provide some benefits. I don't think re-gearing would change power consumption but not sure. It would make regen stronger. It would affect the computer in several ways. Right now there are some correlations between speed and motor RPM that would get screwed up. It might cause the motor and PEM to generate more heat at highway speeds. I'm sure many of us would love to see you do it so we could see what happens!:tongue:

     
  4. ToddRLockwood

    ToddRLockwood Active Member

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    I wonder if you might pick up some gearbox noise, as the original ratios might have been carefully chosen to cancel noise—as was done on the Segway.
     
  5. vfx

    vfx Well-Known Member

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    I thought Joost and his team has done this. (or know someone who has).
     
  6. rgjones

    rgjones Member

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    oo, do tell please!
     
  7. jeremyz

    jeremyz Member

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  8. omgwtfbyobbq

    omgwtfbyobbq Member

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    If you're interested, I have an octave script hanging around to accurately calculate acceleration. I think you could tweak it a bit to compensate for wheels slip, and have a good idea what changes in gearing will do to acceleration from 0 to whatever.
     
  9. Smop

    Smop Banned

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    This has been done but heat was a problem (which was kinda solved).
     
  10. qwk

    qwk Model S P2681

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    Do you have anymore details?Please do tell.
     

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