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Old 10-21-2009, 10:36 PM   #1 (permalink)
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Mercedes aero engineer: Cd of .20 feasible in production cars within 10 yrs

Found an interesting article about Dr. Teddy Woll, head of aerodynamics at Daimler. There's no date on the piece, but judging by the absense of discussion of the Cd 0.24 E Class coupe, I'm guessing it's older than this year.

He talks about the challenges and opportunities in making cars ever more aerodynamic, which is a stated goal of Daimler - see Mercedes to Sell Super-Aerodynamic Cars in 5 Years | Hypermiling, Fuel Economy, and EcoModding News - EcoModder.com .

Answers questions like:

Which components of cars do you believe have the greatest potential for aerodynamic improvement?

"The big action is at the rear," of course. (No news to EcoModders.) And he describes things the company is doing, and what it could potentially do. Plus chatter about wheels/wheel wells/underbody.

What do you think is the lowest drag coefficient possible for a mass production car?

Spoiler alert: Cd 0.20

He uses the GM Aero - Cd. 0.14 - as a starting point of an "impractical" aero car and lists several of its unacceptable aero features that would need to be compromised for reasons of safety/performance/practicality.

Not sure if he's referring to this car "GM Aero 2000"



Anyway, worth a read:

"A Drag Coefficient of 0.2 Represents the Sound Barrier" - ATZ online

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Old 10-21-2009, 10:50 PM   #2 (permalink)
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...the date on the picture is "woll_090130.jpg" which seems to imply Jan 30 2009, so it could've been late 2008 or early 2009.
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Old 10-21-2009, 11:34 PM   #3 (permalink)
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Quote:
In the 1980s, a few prototypes were created that were used to sound out the limits. For example, the GM Aero had a drag coefficient of 0.14. It had completely smooth wheels and a completely smooth underbody. The angle of the windscreens meant that it heated up to very high temperatures in the sun and it had no brake cooling, no cooling air system and no seams on the bodywork. If you were to use this shape, which would not fit into a standard garage, to create a production car, you would have to add at least 30 or 40 points, which would bring the drag coefficient up to 0.18. If you then shortened it to a length that is suitable for everyday use, the figure would increase to 0.2.
That is confusing- his comments about the GM "Aero".

The Aero X certainly looks garageable... has body seams... so it shouldn't be that.

The Aerotech- especially the longtail- is long enough not to be garageable... has no seams really... but it's obviously not a road car... has no back window either... has cooling openings...



Maybe his memory has failed him and he's got these two cars combined in his mind? Or there's another GM aero car we don't know about?

Quote:
The length of the rear end can reduce drag by between five percent and a maximum of 15 percent. However, in the case of a 15 percent reduction, the rear end would be so long and narrow that it would probably be difficult to get a suitcase into it widthways.
A perfectly designed full boat-tail on my Tempo would get me from .36 to .306? I thought they were potentially worth more than that...
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Old 10-22-2009, 12:21 AM   #4 (permalink)
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Good web detective work. I use that trick too from time to time.

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Old 10-22-2009, 07:38 PM   #5 (permalink)
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Lets see. I have a car that has no problem fitting in a garage, has no problem with excessive heat buildup inside from the angle of the windshield, no problem with brake cooling, has a cooling air system (is he talking about the engine radiator or the A/C?), and is practical enough for daily driving all year around. And its Cd is.....
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Old 10-22-2009, 09:24 PM   #6 (permalink)
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...there's INSIDE-the-company mindsets and OUTSIDE-the-company mindsets.

...let me guess, Dr. Woll's was INSIDE "M-B" and not INSIDE "GM" for sure.
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Old 10-23-2009, 03:20 AM   #7 (permalink)
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i recentyl came accross this article about the pinafarina aero car experiment with an 0.201 Cd it wouldn't look even half as unconventional today as it did back than.

Popular Science - Google Boeken

also it just seems to get the basics right, and without compromising practvality or intyroducing shapes that would be difficult to make.

if you start with the best possible shape and that make a few compromises to turn it into a car you'll always end up with something better than when you make a car and than compromise the styling to get it a bit aero
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Old 10-23-2009, 06:02 AM   #8 (permalink)
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Quote:
Originally Posted by lunarhighway View Post
i recentyl came accross this article about the pinafarina aero car experiment with an 0.201 Cd it wouldn't look even half as unconventional today as it did back than.

Popular Science - Google Boeken
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Old 10-23-2009, 12:32 PM   #9 (permalink)
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I always thought the Ford Probe V was a good looking car, and only 25 years old!





It had a .137 cd and doesn't look as if it would be too difficult to produce today.
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Old 10-24-2009, 09:59 AM   #10 (permalink)
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What ever happened to that Benz Boxfish prototype?

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