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S90D Handling Under Acceleration

Discussion in 'Model S: Driving Dynamics' started by Jeff-6293, Jan 4, 2017.

  1. Jeff-6293

    Jeff-6293 Member

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    So, I have my brand new red beauty with 4 Happa R2 snows and am beginning to learn its foibles and desires. Many wonderful learnings, but I'm a little surprised by its handling when I do a fairly strong acceleration from a stop. (All examples are on dry pavement.)

    For comparison, I've just come out of an Audi A7, and while it can't match the S90D it always felt perfectly stable under any acceleration. My Tesla though, if I'm heavily accelerating into a turn (e.g., leaving a parking lot and spooling up to merge into 55 mph traffic on a non-divided highway), feels like the rear end is taking most of the load, leaving the front end (read steering) feeling a little under-controlable.

    Is this just me, or is this common since, I assume, the heavy acceleration does indeed place more of the weight on the rear wheels?

    Thanks for the insights.
     
  2. Haxster

    Haxster Member

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    Takes some getting used to. A tight grip on the steering wheel is essential during hard acceleration; especially if in a turn.

    This is my first all-wheel drive car with so much power (MS 90D), but I've never experienced this much torque steer on FWD or high performance rear wheel cars.
     
  3. thegruf

    thegruf Active Member

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    I believe if you have Range Mode (in the settings) "On" the front motor is used with the rear motor supplementing the power as needed.
    With range mode "Off" it is the other way around, with the rear motor being used most and the front motor being called in as needed.

    I never found any noticeable difference in range between on and off setting, but I prefer Range Mode off as you do get a noticeable bias to rear wheel drive (and as a side benefit you get less motor whine from the front motor).

    Maybe play with this setting to see if you have a preference.

    You also don't state if you have air suspension or coils, this can also be a substantial differentiator in handling.

    And yes, don't forget the S90D is acelerating much harder than the A7 if floored at low to medium speeds so absolutely you will feel it squirm a bit more
    enjoy :)
     
    • Informative x 1
  4. ecobon

    ecobon Member

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    Mine feels that it's oversteering quite a bit during hard acceleration. Something that I got used to after a day or two of spirited driving.
     
  5. ColBatGuano

    ColBatGuano Member

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    Your Audi had Torsen differentials in the front and rear axle (also in the driveline between axles, if memory serves). The Tesla has open differentials. Watch a few YouTube videos and you will see why this matters on slippery surfaces and in turns. Anytime one wheel wants/needs to rotate faster than the wheel directly across the car from it the Torsen differential will have more control than the open differential.
     
  6. RDoc

    RDoc S85D

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    I don't think snow tires are the best for testing and/or pushing handling.

    From what I've seen with our 85D, the handling under power is reasonably smooth, and with the low center of gravity, the car handles well for what it is. However, if I was less interested in the car's ride comfort (and my wife would put up with it), I'd put much higher performance summer tires on it. The limit is clearly the tires.
     
  7. Haxster

    Haxster Member

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    Just drove a P90D Model X. Virtually no torque steer…especially compared to my MS 90D.

    I wonder if it could be the larger rear motor on the P90D?
     
  8. AWDtsla

    AWDtsla Active Member

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    I've never noticed torque steer.

    Also front/rear torque split is entirely up to the firmware du jour. No telling what the behavior of the car should be or will be.
     
  9. Jeff-6293

    Jeff-6293 Member

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    I have air suspension.

    So – a new term for me, "torque steer". No question that my Tesla has vastly more torque than the Audi but I was still surprised at how it responds. Perhaps that's the nature of the beast, but I would think a well-behaved software controlled car could address this.
     
  10. J1mbo

    J1mbo Member

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    It is very easy to lose traction with winter tyres at any speed, and not always obvious that this has happened due to the reaction speed of the traction control system. Maybe this is what you were feeling?
     
  11. Boatguy

    Boatguy Member

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    This is the tendency of the steering to require more force to turn the wheels under acceleration, usually only on FWD cars.

    Then as others have noted, snow tires are not very sticky on dry pavement, they are going to get loose a lot earlier than all season or real performance tires.

    But just to clarify, is the car really not going where pointed, or it is the wheel just feeling a little light? Try changing the steering mode and seeing if it changes the feel to something you prefer.

    That said, my Porsche Carrera 4 was very hard to get loose and under hard acceleration, it would pretty much go the way it was pointed. However, hard acceleration at lower speeds in a turn (i.e., < 50) was a way to induce some understeer (a far cry from my earlier 911's!). Basically the rear is pushing through the front because the front tires can't have the same grip as the back when they're turned significantly away from the direction of travel which is the case at lower speeds.

    So my belief is that yes, you could definitely induce some understeer with snow tires on dry pavement under hard acceleration in a turn at lower speeds.
     
    • Like x 1
  12. Blu Zap

    Blu Zap Grinning member

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    AWD tends to have oversteer vs. RWD understeer. I am used to a P85+ RWD. I recently drove a P100DL rocketship. The nose rose under acceleration actually taking weight and traction off the front end. Steering became very light and it was clear we were going where it was pointed at the moment of launch. A bit of finesse is needed to keep all wheels doing what you want them to do under heavy torque! Otherwise it will go just as pointed!
     

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