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CC Advertisers
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 2Likes
10-01-2009, 12:53 PM
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Half-Ass Member
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Join Date: Jun 2005
Cobra Make, Engine: ERA #732, 428FE (447 CID), TKO600, Solid Flat Tappet Cam, Tons of Aluminum
Posts: 22,025
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Not Ranked
... and it's harder than you think to tell just by looking
Most people would bet that a Lamborghini Countach would not have the same CoD as the Cobra, when actually they're very, very close.
Last edited by patrickt; 10-01-2009 at 12:58 PM..
Reason: Added the pic
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10-01-2009, 03:33 PM
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Senior Club Cobra Member
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Join Date: Jun 2007
Location: Covington,
wa
Cobra Make, Engine: Superformance # 532, 466 BB, 560HP
Posts: 3,029
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Not Ranked
It's better than a 4 X 8 sheet of plywood, but not by much.
__________________
John Hall
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10-01-2009, 05:02 PM
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CC Member
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Join Date: Feb 2006
Location: Scottsdale,
AZ
Cobra Make, Engine: Superformance, Roush 427R-095, Pro Systems carb, 2" headers, Buckshot Racefab side pipes, 10s off idle start
Posts: 705
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Not Ranked
I figured it out a while ago based on rear wheel HP on a dyno and then HP loss at speed using a G-tech compition meter. It does look to be over .4 as mentioned. The usable HP at higher speeds has a huge loss from resistance. Over 120 or so mph it becomes a real challenge and even seems to require diffrent jeting there's so much load.
This is third gear with a few charts and assorted changes. It came out to be about 100 HP of energy loss around 110 mph. The faster you go the loss becomes exponential. The car on the dyno was making about 475 at the wheels when it made about 340 or 350 in motion of usable power.
Here's a formula.
http://www.gtechprosupport.com/support/AeroDragCalc.php
Last edited by greg schroeder; 10-01-2009 at 05:31 PM..
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10-01-2009, 06:56 PM
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CC Member
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Join Date: May 2007
Cobra Make, Engine: JCF supplied the body,frame,and some of the driveline-I completed it to be a very accurate 289 slabside
Posts: 149
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Not Ranked
The drag coefficient Cd has nothing to do with the size of the car,only the shape. The total drag force is proportional to the frontal area times Cd times speed squared.
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10-03-2009, 04:17 PM
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CC Member
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Join Date: Feb 2006
Location: Scottsdale,
AZ
Cobra Make, Engine: Superformance, Roush 427R-095, Pro Systems carb, 2" headers, Buckshot Racefab side pipes, 10s off idle start
Posts: 705
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Not Ranked
Quote:
Originally Posted by jon@harrison.ne
The drag coefficient Cd has nothing to do with the size of the car,only the shape. The total drag force is proportional to the frontal area times Cd times speed squared.
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Here's that formula again. It's pretty cool to see the HP loss value at speed.
http://www.gtechprosupport.com/support/AeroDragCalc.php |
03-22-2012, 03:38 AM
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CC Member
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Join Date: Jun 2000
Location: Cape Town, South Africa/Mainz, Germany,
Posts: 1,601
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Not Ranked
Drag
Good morning!
Sorry to reanimate an old thread, but years ago we had a nice discussion about all of this. That thread got lost, but the frontal area is 16.6 sqft, the Cd of drag is about 0.6.
We couldn't determine the real value because it's a part of total drag and it's changing when the car lifts at speed (as does the frontal area).
In essence, Cd (coefficient of drag) is a variable, most likely from 0.55 to 0.65 for a Cobra.
To go 180mph you need 430Hp, with a hardtop and open windows (that's how we tested in 1995). Side note: If you reduce your windshield size to a single seater you need only about 320Hp to drive 180mph. That should improve your 1/4-mile time too.
__________________
If I don't respond anymore, that's because I can't log in
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03-22-2016, 02:18 PM
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CC Member
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Join Date: Apr 2012
Location: Bay Area (Peninsula),
CA
Cobra Make, Engine: ERA 427, 427/487 side-oiler
Posts: 1,248
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Not Ranked
Quote:
Originally Posted by jon@harrison.ne
The drag coefficient Cd has nothing to do with the size of the car,only the shape. The total drag force is proportional to the frontal area times Cd times speed squared.
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Isn't is proportional to speed cubed? |
03-22-2012, 11:51 AM
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CC Member
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Join Date: Jan 2008
Location: Sacramento, CA,
Posts: 636
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Not Ranked
Quote:
Originally Posted by patrickt
Most people would bet that a Lamborghini Countach would not have the same CoD as the Cobra, when actually they're very, very close.
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Perhaps its those wiide tires. |
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