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Car And Driver magazine's drag coefficient measurements

Discussion in 'News' started by MartinAustin, May 29, 2014.

  1. MartinAustin

    MartinAustin Active Member

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    The Slipperiest Car on the Road | Blog | Tesla Motors

    I'm reminded of the scandal with the manufacturers providing fuel economy numbers to the EPA. They all make their own numbers up (or, use some sort of testing that is peculiar to each manufacturer and are not equally-weighted, like an independent measurement would be). Only when they are truly ridiculous do they get called out for making up fictitious numbers.

    It's good to see coefficients of drag getting independently measured on the same equipment. Kudos to Car And Driver. Now we can really compare them. The Mercedes CLA250 measured number of 0.30 seriously calls into question Mercedes' own claim of 0.23, which is a significant difference. By comparison, right in line with our understanding of Elon Musk - who gives it to us straight, warts and all - the Tesla claim is 0.24, and Car And Driver measured 0.24.
     
  2. jerry33

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

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    My guess would be that MB is measuring just the body shape without the undercarriage and it's aerodynamically inefficient parts. It's easy to get very low numbers then.
     
  3. yobigd20

    yobigd20 Well-Known Member

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    odd that they measured the P85 to have 0-60 in 4.6 seconds and a quarter mile times of 13.3. that seems very slow compared to every other 0-60 and 1/4 mile measurement I've seen of a P85. then again, the one pic shows that they are using 19s. and its an early 2012 model. therefore, probably crap-ass goodyear tires that slip under full accel.
     
  4. 3mp_kwh

    3mp_kwh Member

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    The 0-60 times can depend upon the "1 foot roll-out", and whether it is included/excluded at the start.
     
  5. stopcrazypp

    stopcrazypp Well-Known Member

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    The article explained why. The US version of the CLA does not have the active grill shutters that the European version does. So it's still possible that the European version does have such a low drag coefficient.
     
  6. jkliu47

    jkliu47 Member

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    A statement in the last paragraph is interesting -

    "With taller gearing, a P85 Model S might reach 200 mph"

    Could this be the German spec Model S of the future?
     
  7. sbronle1

    sbronle1 Member

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    I saw that comment too and was wondering... "top speed is redline limited?" Is there really a limit? No one except a driver on a race track, someone drunk, or someone running from the law would ever drive that fast. It kind of reminds me of that old Nissan 200 commercial that ends by saying something like "you will never drive 150 mph but at least you know you could." Given the current size of the motor in a MS is only about the size of a gallon of milk minus the inverter, surely a larger one could ensue. Just thinking...
     
  8. AlexT

    AlexT Member

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    Aren't they often (software) limited to 156 mph (250 km/h)?
    I would be curious to learn how it affects battery drain and temperature.

    Centrifugal forces may pose some limits on engine parts.
     
  9. SebastianR

    SebastianR Member

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    Yes, they are. And then there is a whole host of companies that makes good money removing that limit...

    I guess the bigger problem is that at 160mph the range of a P85 would look more like that of an i3 (at much lower speeds - granted)
     
  10. MartinAustin

    MartinAustin Active Member

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  11. Robert.Boston

    Robert.Boston Model S VIN P01536

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    My understanding is that the limitation at 130mph is not just to limit energy consumption but also because of the RPM of the motor. To be able to sustain speeds above 130mph, Tesla will need to change the gearing ratio (or add a multi-speed transmission, unlikely).
     

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