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Old 05-29-2014, 08:47 PM   #1 (permalink)
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Car & Driver Aerodynamics Test

This is great! Mainstream car magazines are picking up on what we already know: aerodynamic drag is critical to car efficiency.

http://www.teslamotors.com/sites/def...n-the-road.pdf

Aerodynamic Tesla Model S Electric Car Wins The Wind-Tunnel Wars

Wind tunnel contests!

Bring 'em on!

Quote:
Interestingly, only the Model S and Volt lived up to their official drag coefficient numbers, of 0.24 and 0.28 respectively. The Prius missed out by a hair, at 0.26 compared to an official 0.25.

The Leaf, Mercedes, and old Insight were all significantly higher than their official figures, however.

Nissan's car returned a 0.32 figure in the wind tunnel, against an official 0.28. The Insight should have matched the Prius at 0.25, but came back at 0.30, and the CLA matched that figure--missing out significantly on its official 0.23.

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Old 05-29-2014, 10:06 PM   #2 (permalink)
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More proof we shouldn't get too hung up on small published Cd variations; who knows if they're accurate anyway?
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Old 05-29-2014, 10:16 PM   #3 (permalink)
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How is the Insight worse than the Prius?
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Old 05-29-2014, 10:50 PM   #4 (permalink)
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I'm more inclined to think the "differences" could be the result of 'static' (no tires rotation) versus 'dynamic' (dynamometer) wind tunnel testing techiques. Spinning wheels create eddy currents which create a LOT of drag!

Last edited by gone-ot; 05-29-2014 at 11:16 PM..
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Old 05-29-2014, 11:32 PM   #5 (permalink)
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The guys at Green Car Reports should read Road & Track once in a while--they were the only publication I know of to accurately report Mercedes' claimed drag coefficient for the CLA250 (the only version available in the US, in addition to the AMG) of .28, not .23 (straight from the horse's mouth here).
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Old 05-29-2014, 11:44 PM   #6 (permalink)
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.30 for the 2001 insight? uh think again people.
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Old 05-30-2014, 12:12 AM   #7 (permalink)
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That CLA number looked bogus from the beginning. Nice to see a test of it. .30 instead of .23! I wonder how much could be innocent variation between testing facilities? Any of it?
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Old 05-30-2014, 11:18 AM   #8 (permalink)
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What's with the .30 Cd on the Gen 1 Insight?
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Old 05-30-2014, 12:43 PM   #9 (permalink)
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Quote:
The expert in charge at our clandestine test location explains: “All wind tunnels strive to accurately quantify the aerody- namics a car will experience in the real world. The vehicle and the tunnel consti- tute a system with complex interactions. As a result, drag and lift measurements on a particular vehicle can vary from one tunnel to another.”
They name the cars but they decline to name the tunnel? What are the odds it's A2?

The car that costs 3x as much has better aero? I am shocked.
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Old 05-30-2014, 01:13 PM   #10 (permalink)
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The *information* that I thought MOST USEFUL was their listing of aero power at 70 & 100 MPH:

14 HP @ 70 MPH; 42 HP @ 100 MPH - Tesla S P85
14 HP @ 70 MPH; 42 HP @ 100 MPH - Toyota Prius (GenIII)
16 HP @ 70 MPH; 45 HP @ 100 MPH - Chevrolet Volt
16 HP @ 70 MPH; 48 HP @ 100 MPH - Mercedes-Benz CLA-250
18 HP @ 70 MPH; 53 HP @ 100 MPH - Nissan Leaf SL

...that's two KNOWN points on their respective aero curves!


Last edited by gone-ot; 05-30-2014 at 03:14 PM..
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