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How is it that D cars are so good in snow and ice???

Discussion in 'Model S: Battery & Charging' started by sorka, Jan 31, 2017.

  1. sorka

    sorka Active Member

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    A few weeks ago we went up to our lodge at Dodge Ridge(across the parking lot from the resort). We didn't take the Tesla because the right rear door window had shattered the night before so we had to take the Prius.

    There's a steep driveway covered with ice. Even with tire chains the Prius couldn't even come close to making it up.

    Yesterday we went up again for a Monday ski day. Conditions were the same with just as much ice (even more actually) on the driveway. But the Tesla went up without any slippage and did so without tire chains. It's like the ice wasn't even there.

    So my question is, without a locking side to side diff, how can the D cars be so good on ice on a hill? If one wheel slips even just a little, that wheel should get all of the power and the other wheel on the other side should be stuck.

    This is why limited slip diffs are better than open diffs for traction in snow and mud. Does the insane amount of micro torque control compensate by preventing the slip from even occurring?

    Mind you, I'm not complaining.....at least about the Tesla. The Prius on the other hand is officially the worse snow car on the planet!
     
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  2. chillaban

    chillaban Active Member

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    Part of it is the high frequency/resolution control of the front vs rear torque. Being able to apply torque to the end of the car that currently has traction is really important on icy / snowy surfaces where traction conditions are constantly changing, and the electric motors can react a lot quicker than a traditional transfer case.

    But in terms of side to side, a lot of new cars these days handle those situations very well with differential braking. ABS is constantly applying braking to individual wheels to curb wheelspin and keep your open diff working as expected. In a lot of cases it can be faster than an electronic limited slip diff. The main downside is that you are wearing out your brakes quicker, and sustained driving in low traction environments may even cause your brakes to overheat.

    But again, that all needs to be balanced with the cost of brakes vs cost / complexity of a limited slip diff and truck-like 4WD system. Overall, I think for passenger cars, Tesla's design is a net win, and reminds me of the newer Quattro/4MATIC/xDrive approach too.
     
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  3. sorka

    sorka Active Member

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    Ahh yes. I forgot about using breaks to control the spin of the wheel starting to lose traction. If the response is fast enough that would clearly be much better than using an LSD.
     
  4. CanuckS#69

    CanuckS#69 Member

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    There's a video floating about somewhere of someone doing a cross-axle ditch in a Model X that exhibits exactly how good the control is. I would say that it is substantially *more* effective than even off-road limited slips and approaches the ability of a full locker. A wheel off the ground with the opposite wheel on will spin lazily, then stop while the opposite wheel applies full torque. At no point do you see loss of traction result in high speed wheel spin on a single wheel, which is what causes loss of control. I'd love to see an actual off-road truck with Tesla drivetrain bits, it'd be a monster.
     
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  5. sorka

    sorka Active Member

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    This one?
     
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  6. HankLloydRight

    HankLloydRight Fluxing

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    That's freaking awesome! I assume a D Model S would behave in a similar fashion?
     
  7. Saghost

    Saghost Active Member

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    I would expect it to - as far as we know the powertrain and programming are the same.

    As someone said upthread, a "Tesla Jeep" would be an amazing off-road vehicle - my X technically has similar ground clearance to the Suburban I took into mild off-road environments, but it really doesn't have the clearance or suspension travel for anything beyond fairly flat trails.
     
  8. DFibRL8R

    DFibRL8R Member

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    Very impressive video. D+winter tires+air suspension=amazing winter off road performance potential!
     
  9. bhzmark

    bhzmark Active Member

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    Another possible explanation is different tires and/or slightly different conditions between the two days. A little change in temp or character of ice can make a big difference. My D was stuck going up an icy hill when I had OEM all seasons instead of winter tires.
     
  10. sorka

    sorka Active Member

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    I had just installed Pilot Sport A/S 3+ which aren't OEM but tire rack consumer 9+ rating scores in every category except ice and snow which is only 7.7 but that's still good for an all season tire.
     
  11. JasonA-EV

    JasonA-EV Member

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    I can't wait to take mine up to the snow this weekend!! Awesome video! Thanks for that!
     
  12. sorka

    sorka Active Member

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    Strange. This isn't in the right forum. Pretty sure I started it in the parent.
     
  13. Villa-Lobos

    Villa-Lobos Member

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    also the weight distribution is almost 50/50 were an ICE is 65/35 because of engine/transmission. that makes a big difference also having a motor on each axel sounds way more efficient than applying braking systems
     

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