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Range isn't what needs attention...

Discussion in 'Model S' started by Eclectic, Mar 19, 2015.

  1. Eclectic

    Eclectic Member

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    I can't say I've ever had an issue with range anxiety, and I drive my P85D on longish trips fairly frequently. What needs to be addressed is acceleration on the P85D.

    0-60 is fine. 0-80 is fine too. Maybe fine is an understatement. But 40-90 or 60-100, etc. is not up to snuff. For a car with this much HP and torque, the relative gutlessness at higher speeds is glaring.

    For those who are going to tell me that I shouldn't be speeding, thanks for your advice. I understand. No need to say it more than once.

    But for those of us who expected this kind of advertised power to translate into performance at higher speeds, the problem is pretty significant.
     
  2. SW2Fiddler

    SW2Fiddler Bannd Member

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    #2 SW2Fiddler, Mar 19, 2015
    Last edited: Mar 19, 2015
    "Relatively Gutless" is the new "Lame" - thanks, that does sound a bit better! I understand the meaning of 'relative' -- I get it.

    It's possible that only a gearshift setup would help this issue. No, it wouldn't need as many different bands as an ICEmobile, but how else would you translate performance from the nice lower velocities to the upper ones you crave?
    (See? I avoided saying what you thought I was going to say XD )
     
  3. point1

    point1 Member

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    Only way to adress that is with a gearbox, I think it would be a good idea with maybe a 3-speed gearbox. That should be sufficient.
     
  4. Eclectic

    Eclectic Member

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    I was being a bit facetious with the complaint...but yes, the transmission kickdown effect is exactly what I'd like to feel when I step on it at high speeds.

    I assume that there would be some tradeoff for more speeds, but I'm a lawyer, not an engineer, and I have no idea how these things play out. If anyone knows, what would we have to give up to get better high speed acceleration?
     
  5. point1

    point1 Member

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    Some extra weight to account for a gearbox. Or you could change the current gearing, but that would mean slower initial acceleration.
     
  6. Lump

    Lump Active Member

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    Trying to come up with a proper name for this..gutlessness anxiety doesn't flow.
     
  7. qwertzy

    qwertzy Member

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    The low end instant acceleration, the direct driveness that was touted with the transmissionless Regera.

     
  8. bp1000

    bp1000 Member

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    Is it that you are just use to brutal accelerations from a stop, you are expecting the same forces and torque from a rolling start? As mentioned gearing would help with this sensation but it will add weight.

    I havent seen hardly any rolling acceleration tests but i did see a british mag pitch a p85+ up against a 550bhp aston martin and it destroyed it. From 30mph the aston was in 2nd gear and floored it, the tesla waited then floored it and still beat the aston.

    I think it has the rolling acceleration, it just doesn't feel as brutal.
     
  9. fadkar

    fadkar Member

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    My biggest fear is that I'll find the "overtaking" performance lackluster. I'm hoping the 60-90mph isn't "slow!" Our jaguar xj certainly doesn't have the quick 0-60 speed, but the 60-90 is pretty insanely fast!
     
  10. beeeerock

    beeeerock Active Member

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    What you're doing as you increase speed is increase the kinetic energy stored in the vehicle. The kinetic energy equation is 0.5 X MASS X VELOCITY Squared. That 'squared' term is what makes acceleration from higher speeds feel anemic. Recognize that the motor (or engine in ICE terms) can only convert electricity or fuel into kinetic energy at a relatively fixed maximum rate (forgetting power curves).

    So going from 0 to 50 would require (in simple terms) 2500 units of energy. However, 50 to 100 would require ANOTHER 7500 units of energy. So you'll never enjoy the kick in the pants when you mat it at 50 as you do from 0!

    For the same reason, a panic stop eats up way more distance from 100 to 50 than it does from 50 to 0!
     
  11. Stoneymonster

    Stoneymonster Active Member

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    Please no gearbox, I like having fewer things to break. Note also that the original roadster had one and destroyed itself from the torque.
     
  12. krisg81

    krisg81 Member

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    I kind of agree with you on this. I went from a P85 to a P85D and the biggest difference is in the launch. From 30MPH+ rolling acceleration, I swear the P85 felt slightly quicker. I am not sure why, but it just doesn't feel as quick as the P85 from a roll. The P85 puts you in your seat harder from a roll, it just seems the front motor on the P85D isn't doing anything except when launching.

    The launch is totally worth it though. It just doesn't feel like all 691 horses are at work unless its from a dead stop. I wish there was a way to tell..
     
  13. point1

    point1 Member

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    Off course, but the problem (at least for the OP) is that the engine in the Tesla doesn't have it's peak torque when at high rpm (like an ICE), thus it feels slower than another 700 hp car with a gearbox would do at speeds like 60-100, especially when you don't have a gearbox. However since the Tesla has 2 engines now, adding a gearbox would be more complex, at least if you are gonna place one engine at the front and one at the back.
     
  14. donv

    donv Member

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    I thought part of the idea of the "D" was that the front engine would be geared differently than the rear engine, to give both better efficiency at high speeds, and presumably more power as well?
     
  15. invisik

    invisik Member

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    The small motor up front has to max out sooner then the rear larger motor... at higher speed the front motor probably isn't contributing much to acceleration.

    It sounds like it needs a third motor that starts to kick in at 60 mph at the beginning of it's torque curve. (or a gearbox, which I also don't really want)

    -m

    PS: This is starting to sound similar to the concept of multiple sized sequential turbochargers on a diesel to keep the lag to a minimum and smooth out the power curve
     
  16. krisg81

    krisg81 Member

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    You can't really have two different geared motors working together, just like an AWD or 4WD system can't have different gear ratios in their differentials. It is possible, but they couldn't work together/at the same time. The only way for it to be possible would be to have the rear motor launch you, then it shut off as the taller geared front motor turns on- like a 2 stage system. If the P85D had the same 470HP in the front as the rear motor, this would be a great system-except AWD launches and AWD in general wouldn't work.

    The solution would be a 691 single electric motor with a transfer case and differential, thus making AWD. Give it a 2 speed gearbox (2nd gear shifts after 65-75MPH, there is so much torque you wouldn't need more than 2 gears) and the car would truly be .. INSANE.
     
  17. Saghost

    Saghost Active Member

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    #17 Saghost, Mar 19, 2015
    Last edited: Mar 19, 2015
    What gives you this idea? On separate inverter, connected to different sets of wheels you can absolutely have two motors geared completely differently, and while we have no definite proof yet I believe the accepted opinion of the forum is that's what the P85D has.

    The two drive trains have nothing in common downstream of the battery pack, so the gear ratio of one is completely irrelevant to the other. Each can be programmed to add (or subtract) torque independent of what the other one is doing.

    If you look at the video here:

    2014 Acura RLX Sport Hybrid [w/video]

    You'll see an Acura system that's actively trading power between three different electric/hybrid drivetrains - one on the front, and one on each rear wheel with the goal of tightening the car's handling (it's said to be very effective at that.)
    Walter
     
  18. kennybobby

    kennybobby Member

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    Range
     
  19. krisg81

    krisg81 Member

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    Two different sets of wheels? There would have to be a big difference if there is a big difference in gear ratios then.

    I could be wrong here, but I can't see how two different geared motors can run at the same time. I guess that may come from my knowledge of how AWD and 4WD systems with a transfer case and front/rear driveshafts, but maybe with independent electric motors it isn't an issue. I just have not seen anything indicating that is what is happening. In my P85D it seems the front motor assists the initial launch and into the 50-60mph range, then pretty much is non-existent as it really doesn't feel any faster than my single motor P85 above 50MPH. I think any extra power is the rear motor being 470HP vs the P85's 417HP motor. I'll tell you this, from a roll at 40MPH and on there is absolutely, positively, no damn way the P85D feels like it has any more than 50-60HP more than the regular P85, let alone 274 extra horsepower. That front motor isn't doing anything after 50MPH I would almost guarantee it. Maybe if there is traction loss, but other than that- its asleep.
     
  20. Saghost

    Saghost Active Member

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    THERE IS NO TRANSFER CASE.

    The two power trains are completely independent, with no cross connection whatsoever, and thus no issue if one motor turns at half the speed of the other one, as long as the wheels turn at the same speed.
     

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