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Dual Electric Motors - does it reduce range? Possibility of FWD only?

Discussion in 'Model X' started by JakeR, Aug 20, 2014.

  1. JakeR

    JakeR Member

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    Will having two motors reduce the overall range that the Model X can achieve? I know that it is possible that both motors will be running at a much lighter load, but there is more hardware and software involved. Increasing weight and purchase costs. Will the Model X have stronger regen since one of the motors is up front with reduced risk of wheel slippage? I am hoping for a FWD Tesla option at some point with very strong brake-regen. I'd also like to see the charging port up on the front of the car.
     
  2. arg

    arg Member

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    Tesla have said that, contrary to the normal expectation for AWD to reduce range/economy, their implementation actually improves range. This is due to use of different gear ratios for the two motors - such that under cruise conditions the software can direct power to whichever motor is most efficient at that speed and let the other one freewheel.

    Source is videos from various Tesla events - the model X reveal, and an Elon/JB european tour a year or so back. If you seArch other threads on here you will find the links.
     
  3. scottf200

    scottf200 Active Member

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  4. de704

    de704 XP268

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  5. Red Sage

    Red Sage The Cybernetic Samurai

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    As I understand it, the difference won't necessarily be from the gear ratio of the front motor. It will likely be the front inverter that is limited by software to a certain maximum allowance of energy to the front motor. Or, the difference will be that plus a change in gearing, plus a balance of power from the front to rear that changes dynamically as controlled by computer systems that monitor traction, speed, elevation, orientation, etc.
     
  6. Jeff N

    Jeff N Active Member

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    #6 Jeff N, Aug 24, 2014
    Last edited: Aug 27, 2014
    I believe Toyota found that their AWD Hybrid Highlander was more efficient than the FWD version because adding an extra motor to the rear wheels allowed better regen among other potential reasons.
     
  7. bonaire

    bonaire Active Member

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    I think Model III should be offered with Three combinations. FWD, RWD and AWD. I like the idea of front wheel regen braking.
     
  8. JakeR

    JakeR Member

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    I would order a FWD as soon as it was offered if it had super strong regen :)
     
  9. Raffy.Roma

    Raffy.Roma Active Member

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    IMO Model III will be offered with two combinations (like for the Model S). RWD and AWD.
     
  10. wart

    wart Member

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    I've been assuming the Model X will have slightly less range than the S due mainly to increased drag from larger frontal area (higher roofline). But I'm willing to accept the possibility that the AWD drivetrain can be tuned to make up the difference, as others have described above.

    I seriously doubt this will ever happen. The Supercharger stations are laid out specifically to accommodate the position of the charging port on the Model S. I expect all future Tesla models to have the charge port in essentially the same place.
     
  11. JakeR

    JakeR Member

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    That's too bad that they might design the charging port location around the super charger. I think most people, myself included, will be charging in our garage at home. I know that side location is ideal for gasoline powered vehicles because it allows us to pull up alongside a fuel pump. But when you have to fuss around in a parking lot or cramped garage, the nose of the car would be the simplest place to plug in. I think I am not alone in this thought: http://venturebeat.com/2012/07/23/tesla-model-s-hands-on/
     
  12. adhawan

    adhawan Member

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    What do you think the torque distribution will be for the Tesla AWD vehicles? It would be nice to have a user adjustable front/rear bias from the touchscreen, something that is not so easily adjustable with a single ICE motor and centre differential. I'm thinking like a slider control such as RWD---75/25---50/50 and then AUTO. Especially in the sportier models, like the third gen roadster, that would be fun- like two cars in one!
     
  13. omarsultan

    omarsultan Active Member

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    Why the desire for a FWD car?
     
  14. RobStark

    RobStark Active Member

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    Anywhere from 100% front to 100% rear depending on what the computer thinks is the best option.

    - - - Updated - - -


    Gasoline station type superchargers are ideal for the side location.

    tesla-supercharger-fast-charging-system.jpg


    Typical charger point layout superchargers are ideal for front position charging ports.

    Tesla-Supercharger-Station-003-e1389591697342.jpg
     
  15. JakeR

    JakeR Member

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    I posted a link to an article describing why the side location for charging is not ideal, but it is awaiting moderation (I guess the link could be SPAM?)

    I think the charging cable needs to be longer for the side-rear location at most public charges, or the driver will need to back-into the spot. In my two-car garage at home the main feed for the 220v line is located in the front of the garage so the electrician put the outlet up there. That means if I park on the left side of the garage, I have to drag the cable across the floor around the driver's side of the car. If I park on the right side of the garage then I have the cable laying on the floor down the middle of the garage with the charging jack sticking out. I don't have a lot of foot traffic through the garage, but walking between the two cars is the favored method of exiting my when we go out for walks and I have to tell the kids to be careful and not step on the cable, or hit the charging jack sticking out of the car.

    - - - Updated - - -

    If had to choose and could only have the drive wheels in the front or the back, I would choose the front for better snow performance and theoretically stronger regen (since the weight shifts to the front of the car when slowing or braking). I am under the impression that having two motors - front and rear would add cost and complexity and the Model 3 is supposed to be aimed at the more budget minded driver.
     
  16. RobStark

    RobStark Active Member

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    AWD drive adds cost but in an EV marginally so relative to an ICEV. And it will increase efficiency or MPGe.

    Complexity? It will be managed by the same computer managing the drivetrain not a complex transaxle spanning the length of the car.

    Model ≡ base is aimed at the more budget minded driver.

    I have not doubt there will be a Model ≡ Performance Plus aimed squarely at wealthy citizens of old cities like London where a car as big as a Model S has a hard time maneuvering in some medieval streets. And some people in suburbia just prefer a 3 Series sized car to an S-Class sized car.

    A front wheel drive car has very little if any advantage in the snow vs a a rear wheel drive car with the weight of the motor above the rear axle and with modern traction control, yaw control, abs etc. And FWD still gives up handling in non-snow weather in the form of torque steer. I seriously doubt we will ever see a FWD Tesla. Even if Tesla makes a tiny city car like Smart it should be rear engined RWD.
     
  17. omarsultan

    omarsultan Active Member

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    I understand the thinking, but you might want to reconsider that if its the only thing holding you back. A big part of the reason FWD gives you better snow traction is because there is a big honking ICE over the drive wheels, which will not be the case with the MS or MX. Based on the youtube videos from our friends in snowier regions, perhaps the best thing you could do for snow traction is to invest in a good set of snow tires.

    The larger issue I see with a FWD Tesla is the amount of understeer you would have to deal with with that much torque going through the steering wheels. I used to have a modestly powered Acura and the understeer on that was noticeable--I cannot imagine trying to manage Tesla-levels of power.

    Of course, AWD addresses both of these issues nicely as well. :)

    O
     
  18. Genebe

    Genebe Member

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    Maybe not in Los Angeles, but here in Chicago, AWD is significantly better in poor weather conditions than RWD (based on my track & street experience with Porsches of both configurations). The torque-steer isn't nearly as noticeable as you would imagine, unless you're a very aggressive driver. On anything less than a track car, AWD is going to be a much better option for a car driven in all 4 seasons.
     
  19. Phil Seastrand

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    I used to drive a Subaru in Iowa winters and I couldn't get it stuck when I tried (and as a college student with not much sense, believe me when I say I tried!). Being able to turn the driving wheels makes a huge difference when trying to maneuver in snow. I passed a lot of rear-wheel cars stuck on the side of the road. AWD is even better.
     
  20. David_Cary

    David_Cary Member

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    AWD will add significant cost. Think what a driveunit costs. Of course the front one can be smaller but this isn't a $500 piece no matter how you look at it. Given the warranty issues up to now, I can see why people wouldn't want double the problems (potentially).

    I personally think greater efficiency with 2 motors will be very small and not worth the cost. Maximizing regen - sure. I think you might eek out .05% with that.

    Torque steer? Would that really be a problem with a traction controlled EV?
     

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