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Old 04-24-2008, 10:49 AM   #11 (permalink)
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Veeeeeeeery nice Tas, and yes thank you!

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Old 04-24-2008, 11:01 AM   #12 (permalink)
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One thing I noted though. In every single case where the frontal area was stated, the 0.81 correction factor on h * w you used gived an overly optimistic figure.

I recall reading a post by phil, must have been of of his aero seminars I'll have to search a bit, where he said to use 0.87 or 0.85, can't remember exactly.

Edit: it was
Quote:
Frontal area can be approximated by multiplying your vehicles width times its height,times 0.84.p
from Aerodynamics Seminar # 6 - by Phil Knox
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Old 04-24-2008, 12:31 PM   #13 (permalink)
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Yeah, I noticed that too. I have updated the calculations to * .84. I have also added the bulk of the list you posted. I still have yet to go through the pdf.
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Old 04-24-2008, 12:36 PM   #14 (permalink)
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Just so you know, the ones I didn't post left in the pdf are mostly exotics.
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Old 04-24-2008, 01:23 PM   #15 (permalink)
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There's a big list at wikipedia that can fill in some blanks.
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Old 04-25-2008, 12:15 AM   #16 (permalink)
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CHRYSLER PT CRUISER LIMITED EDITION 2000
Coefficient of drag: 0.40

FORD SVT MUSTANG COBRA 2003
Coefficient of drag: 0.38

MAZDA MIATA 1998
Coefficient of drag: 0.38

VOLKSWAGEN BEETLE 1999
Coefficient of drag: 0.38
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Old 04-26-2008, 09:22 AM   #17 (permalink)
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A lot of the CdA figures floating around are estimates based on what the estimator thought the Cd might be. Many of the Wiki figures came from the mayfair company website which took a lot from an old version of the cartest program as well as (apparently) estimating a bunch. Accordingly it is hard to say how accurate these are.

I think it would be very helpful if there were some indication in the spreadsheet of where the data came from and whether it is a mfr's number, an independently tested number, or an estimate (and which part, Cd or A or both were estimated).

I'd be interested in knowing where the nology folks got their numbers from.

Without this info it seems like we're really not going to have very good data.

--Steve
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Old 04-26-2008, 12:32 PM   #18 (permalink)
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Well, its definitly no Bible. But, its a heck of a lot better than nothing. Most of my info that I wasn't sure about I double checked against multipule sites. That being said I have used info from tons of different sites since I pulled most of the info from google. Frontal area is definitly estimated, so this really is a 'best guess'. No offense, I'm not going to go through and source every piece of info. The numbers will vary, but not by that much. You can see generally where your car sits against the pool of cars on the list. So, when someone comes on the site and says they have a frontal area of 19ft^2 you can know that is pretty small.
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Old 04-26-2008, 02:33 PM   #19 (permalink)
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Quote:
Originally Posted by Daox View Post
Well, its definitly no Bible. But, its a heck of a lot better than nothing. Most of my info that I wasn't sure about I double checked against multipule sites. That being said I have used info from tons of different sites since I pulled most of the info from google. Frontal area is definitly estimated, so this really is a 'best guess'. No offense, I'm not going to go through and source every piece of info. The numbers will vary, but not by that much. You can see generally where your car sits against the pool of cars on the list. So, when someone comes on the site and says they have a frontal area of 19ft^2 you can know that is pretty small.
Well, if the goal is just to "see generally where your car sits against the pool" then it might not be worth noting whether the data is wind tunnel or "eyeballed" (to take the extremes). I was just hoping that maybe a little more rigor could be injected by at least noting which numbers came from probably reputable sources vs from "unknown" sources.

Simply checking "multiple" sources doesn't do much--you would need to check independent sources--from what I've seen, a lot of the CdA info on the net is just repeated over and over with the result that very little is independent.

I think your frontal area is better than "a best guess". You've at least documented how the number was arrived at and if someone has a reason to use a different algorithm, they can do so since you provide the raw info (width, height).

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Old 04-26-2008, 04:19 PM   #20 (permalink)
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frontal area

Quote:
Originally Posted by tasdrouille View Post
One thing I noted though. In every single case where the frontal area was stated, the 0.81 correction factor on h * w you used gived an overly optimistic figure.

I recall reading a post by phil, must have been of of his aero seminars I'll have to search a bit, where he said to use 0.87 or 0.85, can't remember exactly.

Edit: it was from Aerodynamics Seminar # 6 - by Phil Knox
.84 was from "ancient" text,and Hucho's more current 0.81 multiplier reflects the industry use of more tumblehome in modern rooflines.I've glanced at a few semi-current CAR and DRIVER mags and they're reporting some "official" frontal areas that work out in the ninety-percent region,further confounding the likes of aero-modders in search of accutate quanta.Rats! I used to be more current,had subscriptions and everything.I got turned-off by all the paid advertising and let all my subscriptions lapse.Sorry!

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