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RWD launch limit

Discussion in 'Model 3: Driving Dynamics' started by Wy2sl0, Jan 5, 2020.

  1. Wy2sl0

    Wy2sl0 Member

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    Hi everyone,

    Just curious if anyone has found out how much Tesla is limiting the launch on the RWD model? I've seen quite a few dragy times and they all seem to be pulling 2.1-2.2 60' times which is honestly quite terrible for an electric car where power is supposed to peak at stall speed.
    I would be curious to know if there is some ECU limitation due to slip? Or if anyone has tried slicks/drag radials on the back?
     
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  2. JulienW

    JulienW Active Member

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    The RWD only has the reluctance permanent magnet motor. While still quick it is a little slower starting up. The AWD/Performance also have an induction motor (front) that has near instant startup torque. This pulls the car forward and this helps the reluctance permanent magnet motor to torque up even quicker.
     
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  3. ewoodrick

    ewoodrick Well-Known Member

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    There are two RWD motors and the differences are big, specifically the battery. It's the battery that tends to be a differentiator. Smaller battery can't give the same current. There are other design considerations that limit the current as well.
     
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  4. Knightshade

    Knightshade Well-Known Member

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    Eh?

    To my knowledge every installed rear motor we've ever seen on here for a RWD car (LR or SR) has been a 980.
     
  5. AlanSubie4Life

    AlanSubie4Life Efficiency Obsessed Member

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    #5 AlanSubie4Life, Jan 6, 2020
    Last edited: Jan 6, 2020
    Traction is not an issue in a straight line even for the Performance, which is going 60mph in ~3.4 seconds (3.1 seconds).

    It's not that bad.

    The answer regarding relatively slow (compared to P100DL) torque onset appears to be true (even for the Performance), and it might be in small part due to some limitation of cogging, but mostly the SR+ time is limited by software (the battery does not yet appear to be the limiting factor, and it wouldn't be at all for the 0-60' time).

    Remember that power is actually very very low between 0 and 60'. And the power requirement is close to zero when you're traveling close to 0mph, especially in an electric vehicle (in an ICE vehicle the engine might well be putting significant power into warming up the torque converter, or burning the clutch, or melting the tires - but power required to move the car forward from a stop is well below the maximum power available, in all vehicles). The torque, I think, is what you're referring to.

    E.g. at 5mph you're only pulling about 1/8th of maximum power from the battery, in a Model 3.

    Model 3 P3D vs. AWD vs. AWD+
     
  6. ewoodrick

    ewoodrick Well-Known Member

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    Sorry, I was thinking configurations (different batteries)
     
  7. AlanSubie4Life

    AlanSubie4Life Efficiency Obsessed Member

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    #7 AlanSubie4Life, Jan 6, 2020
    Last edited: Jan 6, 2020
    Based on what we know now, the SR+ battery is limited to about 290kW output, or 390HP.

    Currently the SR+ motor does not put out nearly that much power (more relevant, nor is the input power nearly that high). In fact, even on the 3P+, the input power limit to the rear motor is lower than that.

    So it may be that the SR+ is not battery limited at all - it may well be motor limited (but is currently software limited).

    MASTER THREAD: "Acceleration Boost" option, discussion as to which models and how much quicker

    But as mentioned above, this is an aside to the original question, which is really not determined by battery power - you're nowhere near the power limits at launch. Launch vivacity is determined by torque, not power.
     
  8. TMThree

    TMThree Active Member

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    I have LR RWD and the power output on the rear of my car is the same as on the performance. Same motor, same wiring, same battery. Which basically means there won't be a power increase for me unless the performance also gets a boost.
     
  9. AlanSubie4Life

    AlanSubie4Life Efficiency Obsessed Member

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    #9 AlanSubie4Life, Jan 6, 2020
    Last edited: Jan 6, 2020
    Do you have a source for this? I don't think wugz on Reddit has done that testing for the LR RWD, but I don't keep track of the latest LR RWD measurements from the CAN. My impression is that it's close, but likely not quite maxed out, on torque and HP (and that would obviously be a motor limit, not a battery limit). Might be an additional 0.2 seconds on the table if I recall.

    EDIT: Nevermind...looking at the Mountain Pass stuff it does seem pretty close to maxed out now (similar to Performance). Hard to tell comparing CAN bus data to post drivetrain dyno data but seems pretty close to me on both the max torque and the max power.
     

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