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Tesla drag analysis

Discussion in 'Tesla' started by bwilson4web, Jul 26, 2018.

  1. bwilson4web

    bwilson4web BMW i3 and Model 3

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    I was happy to discover the EPA includes entries for EVs in the "Test Car Database" including the roll-down coefficients. This means we can plot the rolling drag power metrics as a function of mph. Using 500 W as the overhead electric load, here are the plots:
    [​IMG]

    [​IMG]
    Each Y-axis value is equivalent of 5 hp.

    [​IMG]
    These are parametric, loss-less, drag power curves at the wheel-to-road interface. I need the kW consumption at 30 mph and 60-75 mph for each model Tesla to correct the fixed overhead and efficiency loss of these curves.

    Bob Wilson
     
    #1 bwilson4web, Jul 26, 2018
  2. el Crucero

    el Crucero Senior Member

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    Interesting graphs based on EPA findings, but anecdotal real world reports seem to indicate that the model 3LR is beating those findings. For example, in chart 3, two separate unofficial tests by separate, independent third parties (one in Colorado, one in Germany) seem to indicate that a model 3LR only uses about 8.25 kWh/100mi at 25mph as opposed to the 11kWh finding of the EPA. I don't know, I'm not smart enough to figure it out. Just an observation.
     
    #2 el Crucero, Jul 26, 2018
  3. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Huntsville AL
    Vehicle:
    2018 Tesla Model 3
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    Prime Plus
    These are 'parametric' curves measured at the tire-to-road interface. Normally we use benchmarks at two, different speeds to adjust for losses:
    • tire flex losses
      • there can be shock absorber losses on poor roads
    • wheel bearing and CVT joint losses
    • differential gear losses
    • reduction gear losses from motor to differential
    • motor losses (lower for PM versus cheaper induction)
    • inverter losses (lower for silicon carbide versus silicon)
    • typical metrics are at the input to the inverter electronics
    Bob Wilson
     
    #3 bwilson4web, Jul 26, 2018
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