Aerocivic - how to drop your Cd from 0.31 to 0.17 - Page 23 - Fuel Economy, Hypermiling, EcoModding News and Forum

Cd · 02-28-2009, 04:47 PM

So, basjoos, does this new low Cd figure improve the .17 figure that you arrived at ?

I never saw any of your coast down testing that you did to arrive at that figure. Did you create a seperate thread, or did I just miss it ?

Also, what is the cars Cd ( yes I know ...point 17, but I mean like .171 or .179 )

basjoos · 02-28-2009, 06:48 PM

The changed OEM Cd figure has no effect on the 0.17 figure since that was determined by coastdown testing done using that spreadsheet from Instructables. Actually my Cd might even be a bit lower than that now as I have installed a number of minor aero mods since doing that coastdown testing. The problem is finding a long enough, flat, and lightly trafficked stretch of road to do the testing on. Its all rolling terrain here, so I have to make a trip down to the coastal plains of SC to do it.

I'd have to pull my original data points out and plug them back into that spreadsheet to get the 0.00 CD figure, but that might be false accuracy since my original data was to the nearest second, not the nearest 0.1 sec.

NeilBlanchard · 02-28-2009, 10:11 PM

Thanks for clarifying how you got the Cd figure. BTW, does the AeroCivic have a full belly pan as well?

alohaspirit · 03-01-2009, 12:50 AM

Everytime I see the Aerocivic I think how cool it would be to see it fully glassed and molded

(maybe even in carbon fibre)

Get rid of all those seams and you could probably knock off .01 or .02

basjoos · 03-01-2009, 08:30 AM

Quote:

Originally Posted by NeilBlanchard

Thanks for clarifying how you got the Cd figure. BTW, does the AeroCivic have a full belly pan as well?

It has a full belly pan. The only parts of the underside that are still exposed to the airflow are the interior side of the wheels. I am still working out a mechanism that would shield the inside edge of the wheels from the wind while not interfering with suspension travel or front wheel turning.

It would be nice is my car's exterior were done in glass, but I don't have any experience working with it and don't have the climate controlled garage it would take to cure epoxy in my humid climate.

NeilBlanchard · 03-01-2009, 09:36 AM

Hi,

I'd assumed it probably did, because any vehicle with a Cd below 0.2 has to, I think.

Can you link to an explanation of the coast-down procedure to measure Cd, please?

basjoos · 03-01-2009, 11:48 AM

Measure the drag coefficient of your car

WV6Z · 03-03-2009, 01:18 PM

Basjoos, I was actually searching for some help with an odd windshield wiper issue on my old '98 Civic and stumbled in..... Just wanted to say beautiful job on the AeroCivic!

Regards,
Tom ~ WV6Z in Anderson, SC

basjoos · 03-03-2009, 06:44 PM

Quote:

Originally Posted by WV6Z

Basjoos, I was actually searching for some help with an odd windshield wiper issue on my old '98 Civic and stumbled in..... Just wanted to say beautiful job on the AeroCivic!

Regards,
Tom ~ WV6Z in Anderson, SC

Hey, a neighbor! I've driven through Anderson a few times in my Aerocivic and visited a small Honda repair shop in the west end of town one time to get some parts. When I pulled into the shop, the mechanic said it looked like the martians were landing as I silently rolled up their driveway with the engine off.

basjoos · 03-03-2009, 06:54 PM

Added another minor aero tweak. I took a page out of Aptera's book and installed ducts to exhaust my cabin air into the small low pressure eddy behind the license plate. I doubt I will notice any difference in mileage, but every little bit helps and it should help to move the cabin air with less fan assist.
Vent holes at back of cargo area.

Other end of ducts opening into area behind license plate.

License plate installed with 1/2" gap behind plate.