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Super range mode

Discussion in 'Model S' started by invisik, Oct 11, 2014.

  1. invisik

    invisik Member

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    Do you think the D could have a super range mode that turns off one of the motors? The rear motor alone should be enough to keep the car going at freeway speeds...... I'd happily trade some performance for 25-50 more mile range.
     
  2. bonnie

    bonnie Oil is for sissies.

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    I think you're missing the part about how dual-motors increases efficiency, not decreases it.
     
  3. invisik

    invisik Member

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    I must admit I am not fully understanding everything about the dual motor setup. Being so much faster and efficient seems opposite to me. Anyone have any links that explain this in more detail?
     
  4. andrewket

    andrewket 2014 S P85DL, 2016 X P90DL (soon 100)

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    Basically, the two motors are different sizes and geared differently. This means they have different speeds at which they will be most efficient. Using software, the D can shift power between the motors to try to hit those peak efficiency points. The net result is the D has a wider speed range where it is more efficient than its single engine counterpart.
     
  5. amzng_ev

    amzng_ev Member

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    I believe that the increase in AWD efficiency is due to the nature of electric motors. They operate at a specific optimal torque and rpm. With the two motors, it needs significantly less torque and RPM. and uses exponentially less energy. Thus, combining the two energy uses, and gear ratios it uses less energy. However, with the S60D and S85D, it is highly possible that the car will be more efficient running just one motor with an optimal gear ratio.
     
  6. David99

    David99 Active Member

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    The torque needed for a given speed is the exact same on the single or dual motor Model S. The dual motor setup just allows for a more efficient use of energy to create that torque. The only single motor range rating is the EPA test, the new ones listed on the website for the dual motors are for a constant speed of 65 mph. It's apples and oranges. I'm sure we will see an increase of range for the dual version on the EPA test, but it won't be as significant as it looks now. But frankly, at the EPA test cycle the Model S is the most inefficient EV on the market. So there is room for improvement.
     
  7. CHG-ON

    CHG-ON Still in love after all these miles

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    "But frankly, at the EPA test cycle the Model S is the most inefficient EV on the market. So there is room for improvement."

    Agreed. But it is sooo worth it.
     
  8. green1

    green1 Active Member

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    Actually, there's probably not much room for improvement, it's the least efficient because it's the biggest and heaviest. Neither of which I'd change for the world. If you took 3/4 of the battery pack out you'd gain a lot of efficiency, you also wouldn't be able to go anywhere, but then again, you'd be just like all the other EVs out there....
     
  9. castor

    castor Member

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    My guessing is that probably a single motor works more stressed creating more heat (loses), two motors works less stressed and give few miles extra range however the car now is heavier, on the freeway the extra weight won’t affect much and I bet you get the extra miles, but in the city I would not be surprised if the car give the same range or even less than a RWD Model S since has to break the inertia with more weight much more often.
     
  10. patn

    patn Member

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    I don't think A/C induction motors like the ones used in the car really have an optimal RPM or torque per se - They are nearly as efficient over a wide range of speeds and loads. However there are losses in the inverter and from heat and other effects in the motor that go up as the current and frequency goes up... So what you are saying is generally right but I think the main advantage is probably lower overall currents in each motor and more optimal power control at the lower speed of the higher geared motor.

    It really begs the question of whether someday a Tesla will have four independent motors - one for each wheel - or if the trade-off of weight vs added efficiency is too high for that case. I'm sure they worked that out long ago.
     
  11. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    As far as I can tell, my Model S gets the same Wh/mi as the Leafs or Volts I've compared it to.

    - - - Updated - - -

    It's more likely to be a space problem. That is, four motors would have to be inboard unless you want a huge increase in unsprung weight. To get back the space for the extra inboard motors, you'd have to move the inverters elsewhere and deal with the additional wiring. Of course, this is how the other manufacturers do it and basically you'd lose the frunk just like they do even though they have just one motor. Electric motors have been around for a long time, so a significant size reduction isn't likely to happen.
     
  12. Johan

    Johan Took a TSLA bear test. Came back negative.

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    Good explanation however from my understanding in the S85D the two motors are the sime sized but likely geared differently.
     
  13. CarlK

    CarlK Member

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    That is correct. I learned the fact that two motors is more energy efficient than a single one when I built my pond waterfall years ago. It turned out that I can use two smaller pumps and use less electricity than if I use a single pump with twice the pumping capacity as the smaller ones. BTW this is likely the reason why the X will have standard dual motor configuration. This is the only way to have it to keep the 265 rated range with the same battery pack as S.
     
  14. AmpedRealtor

    AmpedRealtor Active Member

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    One rear motor gives 265 miles of range. Two motors gives 295 miles of range. What are you asking again?
     
  15. Chris TX

    Chris TX Active Member

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    ^^^This.

    Most people are used to ICE driven AWD/4WD systems causing a hit in MPG. While that's usually true, the way Tesla does AWD is very unique: The front and rear axles are not connected, mechanically. Additionally, the front drivetrain is geared different from the rear drivetrain.

    Imaging having a high HP V8 in the back of a sedan, driving the rear wheels and a low gearset for torque. Then, you had a very fuel efficient I-4 that powered the front wheels using highway gears. On the highway, you would be using the front engine around 70% load and either turning off the rear engine or have it idling. Now, imagine a computer that calculates all the variables to find the most effective combination of engine, gear, throttle position, etc. Sure, there's the added weight of the second engine/transmission, but it's going to be more efficient than just one and MUCH more efficient than one engine driving all four wheels.
     
  16. invisik

    invisik Member

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    I get this and also the part about turning off one motor almost completely when it's not needed. I guess that's what I am getting at. Maybe it does it sufficiently in software.
     
  17. David_Cary

    David_Cary Member

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    - - - Updated - - -

    The same Wh/mi?... I get about 5.2 mi/kwh in a Leaf. That is less than 200 Wh/mi - something no one gets on a Tesla. I may do better than average but no Tesla even comes close. Look at the MPGe numbers - no contest.

    At a certain speed, the model S will do better as it is more aerodynamic. But even given similar drivetrain efficiency, The Leaf is 30% less weight and driving on smaller LRR tires. There is no comparison. I suspect that "certain speed" is 80 mph. So if you drive close to 80 all the time, you may get the same Wh/mi.
     
  18. Saghost

    Saghost Active Member

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    Several EV supercars/concept cars already do this - the original CX-75 (the concept with the jet turbines, not the later cancelled production version, the Rimac, and the Mercedes SLS Electric all have individual wheel motors mounted inboard and on reduction gears.

    I really think this will be the future of EVs. It's a little more weight and cost, but as things improve those penalties will become smaller and the tech will go mainstream. Dedicated wheel motors make it so much easier to handle traction control and regeneration, and it creates a bunch of interesting opportunities to tune the handling of the car (as Honda is experimenting with in the RLX hybrid I'll link below.)

    Four independent inverter/motor sets also means a car that can drive with three failed if necessary. Not ideal, certainly - but the redundancy makes the car almost unkillable - especially with Tesla's RAID approach to a battery pack (though there are still single points of failure in the pack at the contactors and pyro fuse, of course.)

    If the motors get powerful enough and the battery can take it, you won't really need physical brakes, either (except as a safety backup.)

    Here's the RLX review and video. The video is interesting - watch the way the car accelerates one rear wheel while regenerating on the other to tighten turns:
    2014 Acura RLX Sport Hybrid [w/video] First Drive - Autoblog

    Walter
     

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