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Old 06-21-2009, 06:42 PM   #1 (permalink)
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Need Aero Recommendations

Hi Folks,
I would like to submit a couple pics of my car and get suggestions on what I can do to lower CD as much as possible. I'm not scared to cut, fiberglass, bondo. all suggestions mild to wild are welcome. Ignore the front air dam, I put it on to test fit and will be replacing it as soon as I can get to the hardware store.

I have access to a 3d Laser Scanner at work so I hope to get my car scanned and modeled next week and then import it into Solidworks or Ansys to do some CFD simulations on it with various modifications. Just looking for ideas to test and try in the simulation so I don't waste time fabricating something that doesn't work to achieve my goals of .19 or lower CD

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Old 06-21-2009, 10:36 PM   #2 (permalink)
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Hello and welcome to EM,

I would start with a baseline coastdown test to "calibrate" the spreadsheet values, for the tire rolling resistance, etc. And tuft tests to find the problem spots. What is the stock Cd?

You need a full belly pan, rear wheel skirts, and smooth wheel covers. You'll have to work on ducting the cooling air flow through te engine compartment. Does that chin spoiler stick down a lot below the bits on the underside?
Sincerely, Neil

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Old 06-21-2009, 10:44 PM   #3 (permalink)
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You might start with a lower air dam. Ground effects package, spoiler etc. But, if you can, find a fairly large scale model of your car on ebay or something, clay up some modifications on it and scan it.

You may be able to figure out what would work best on your car on a scale model before you go to full scale.

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Old 06-21-2009, 11:13 PM   #4 (permalink)
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To get to .19 or better, you're going to have to mimic the Aerocivic. Aerocivic - aerodynamic mods for maximum fuel economy - aerocivic.com

Full meal deal. Skinny tires, smooth wheel covers, boat tail, full undertray, side mirror delete, the works.

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Old 06-21-2009, 11:27 PM   #5 (permalink)
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The body is already so aerodynamic, I don't know if I'd even do anything to it. Seems like you'd be fine just adding a belly pan and aerodynamic wheels.
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Old 06-22-2009, 08:35 AM   #6 (permalink)
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It may look so aerodynamic, but it is a FAR cry from .19. According to The Mayfield Company Homepage - Coefficient of Drag Tables and Curves, the stock Cd is .30. Like MetroMPG said, in order to get down to .19 you're going to need to throw the whole deal at it.
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Old 06-22-2009, 08:56 AM   #7 (permalink)
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If you want the same cd at night, you will have to radically change the pop up headlights.
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Old 06-22-2009, 10:18 AM   #8 (permalink)
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The Chin spoiler will be replaced with one that hangs down an inch lower to ensure it hangs lower than anything else under the car.

Motivation is Fuel Economy and the challenge of improving the design and of course learning more about aerodynamics.

The Car came with a rear spoiler and windshield wiper which I removed and fiberglassed over the holes, next up will be getting rid of the sunroof. I also filled in the front Vents under the running lights on the nose of the car to smooth it out some. Once I get the car as slippery as possible I will begin tuning the motor for maximum fuel economy with an Innovate Motorsports LC-1 Wideband 02 Kit and Nistune ECU. I have stripped out much of the uneccesary stuff in the car to save weight as well. The car as it sits should be around 2,650 lbs my plans will drop another 200lbs for the weight if all goes as planned with some other mods. I will weighing it shortly to confirm this estimate.

The pop up headlights are not too much of a concern since I rarely drive at night.

Last edited by 240addict; 06-22-2009 at 10:52 AM..
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Old 06-22-2009, 01:27 PM   #9 (permalink)
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plus i know they carry flat headlight conversions
Past Present Future?
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Old 06-22-2009, 03:46 PM   #10 (permalink)
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Why remove the sunroof?

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