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P85D Torque Balancing

Discussion in 'Model S: Driving Dynamics' started by dennis, Jun 1, 2015.

  1. dennis

    dennis P85D

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    I know there have been previous discussions about the P85D using the front motor to "pull" the car forward as you accelerate and unwind the steering wheel from the apex of a turn. That definitely promotes less understeer and faster corner exits.

    After experiencing the understeer that is inherent in heavy sport sedans, including the P85D, I've been experimenting with using the throttle to balance the car while holding the line through a constant radius turn. What I have found is that with a slight application of additional throttle the understeer feeling lessens and the handling becomes more neutral, with a very slight increase in speed. Has anyone else experienced this? Is the same behavior true for the 85D/70D?
     
  2. beeeerock

    beeeerock Active Member

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    I can't honestly say I've been formally experimenting with this, but my impression in my 85D seems to be similar. The understeer sensation diminishes and the car does feel more balanced to me. I'll start paying more attention when the opportunity to push the limits safely arises. I'll be interested to hear if others agree.
     
  3. Danal

    Danal electricmotorglider.com

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    I agree that at neutral thrust (per the power meter), the S will noticeably understeer, just a little bit, as it approaches the edge in most circumstances. I agree that adding bit of thrust seems to help make the car "feel" neutral when it is trying to understeer. Over-application of power has never made the car feel loose (oversteer). Therefore, I have developed the practice in the S to feather in a bit of power whenever I feel anything beginning to let go, without necessarily analyzing just what, exactly, it is doing. Programmed response (from me) in the S. Although, to be fair, I have not made it completely let go yet. Need to find a skid pad, or autocross event*, or something similarly safe.

    Pushing a bit of power is bound to bite me in the but when I occasionally drive my SSR. This is a 5100 Lbs, 400HP, V8, six speed close ratio manual trans, rear wheel drive, limited slip axle, convertible hardtop pickup truck, most recently manufactured in 2006. Interesting behaviors, this beast has.

    Back to the S: As a non-performance sedan, it has been one of the most fun road cars I've driven in a while. I have a way to get to my house where the last couple of miles are a nice little twisty, and a few sections of it can be cleared (and have no intrusion risk to anything bigger than a rabbit, flat open mowed fields both sides). Speed limit is 55, so 61 is safe from LEO. Clear a section, use the S incredible accel, drive that section at chosen speed, slow to safe speed (for both LEO and real safety) before exiting cleared section. What fun!.






    *Just FYI to Tesla owners: Sports Car Club Of America "Solo II", commonly known as "Autocross", goes to great lengths to NEVER use the words "race" or "racing" to help keep insurance, warranties, etc. valid. However, Tesla is the only car I've seen (so far) wherein the written Warranty specifically mentions the word 'autocross' as invalidating your warranty. The "Does not cover..." section includes: "in competition, racing or autocross".
     
  4. beeeerock

    beeeerock Active Member

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    Heh, so Tesla has obviously read the SCCA brochure and circumvented a possible gray area... LOL

    I recall watching a youtube clip from what was likely Top Gear (yeah, I'll avoid comments on that!) in which they had a Mitsubishi Evolution on a track with grass down the edge... drifting turns half on and half off the pavement, with - dramatically - only one finger literally on the wheel. The all wheel drive was advanced enough to manage that situation, apparently quite perfectly. Given the nature of the show, it's hard to know how much was real and how much was Hollywood, but it was a far cry from the unbridled fury of, say, an old Group B Lancia Delta S4. This thread makes me ponder how well the Model S would manage a similar situation.

    I don't think I'm going to try this at home any time soon, but I'm curious all the same. Better to have an idea *before* getting stuck in an unexpected situation.
     
  5. Danal

    Danal electricmotorglider.com

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    It has been raining it TX a lot, so many of my "Insane mode demo rides" have been on wet streets. Sometimes VERY wet. I occasionally feel the car "re-gripping"; even when I feel that, the launches stay quite exciting!

    I haven't tried any serious cornering in variable traction situations. Will have to find a safe place to try that, sounds fun.
     
  6. beeeerock

    beeeerock Active Member

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    Actually, I've done a few here too, in the rain. I'm on uniformly wet pavement though, so the traction situation is probably very comparable at all four corners. I'm very impressed with how little apparent slippage is allowed by the traction control, even when cornering and the weight transfer is left/right rather then just front/back.

    The Tesla engineers have done a remarkable job with this, even though their cup holders suck! :biggrin:
     
  7. CHG-ON

    CHG-ON Still in love after all these miles

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    Oh how I long for rain in CA so I can actually see how my girl will handle. I've had her for 9 months and have still have had no opportunity to see how it is in the wet, aside from mildly damp roads.

    Complete bummer.
     
  8. 3mp_kwh

    3mp_kwh Member

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    Specific to what the OP is asking, the P85D's mid-turn performance is what's being observed (can we leave the drag strip, for one thread?). There can be inputs including steering angle, speed and cornering force, that may all be involved with the power the P85D allows. This is before wheel slippage, and consequently traction control engaging.

    As you drive better, like Dennis :smile:, opening the steering angle means you can apply more power. After a certain point are you finding it? In front? In back? How much? I think there are some answers to unlock about the P85D's settings. To me, it isn't just the selective brake applications, of TC. I think some other limiters are at play before this.

    I haven't driven fast enough that any of these things would be encountered at 40+MPH, but at ~30 something's amiss, and it is much bigger than the difference between "691" and ~500hp.
     
  9. brianman

    brianman Burrito Founder

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    The cupholder count and positions is not something I would blame on the engineers. Designers.
     

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