 Drag Coefficient, and other parameters wanted |
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| astronomerdave |
 Nov 6 2009, 01:21 PM
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#1
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Member  Group: Members Posts: 69 Joined: 26-January 09 From: Los Angeles, CA Member No.: 9,979 Region Association: Southern California  |
Does anyone know where I can find this information (for '72 914/4) ? . . .
Thanks, --Dave |
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Replies(1 - 19)
| Elliot Cannon |
Nov 6 2009, 01:36 PM
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#2
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914 Guru Group: Retired Members Posts: 8,487 Joined: 29-December 06 From: Paso Robles Ca. (Central coast) Member No.: 7,407 Region Association: None 
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A number of years ago, someone did some wind-tunnel testing on a 914 to determine drag coefficient. Anyone remember who that was?
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| SirAndy |
Nov 6 2009, 01:41 PM
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#3
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Resident German Group: Admin Posts: 41,676 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
QUOTE(astronomerdave @ Nov 6 2009, 11:21 AM)  Does anyone know where I can find this information (for '72 914/4) ? . . . I don't have the data handy (i'm at work) but the 914 CD has been posted here before. If i recall correctly, it's slightly better than a 911 turbo ... (IMG:style_emoticons/default/popcorn[1].gif) Andy |
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| SirAndy |
Nov 6 2009, 01:44 PM
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#4
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Resident German Group: Admin Posts: 41,676 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
The search works! (IMG:style_emoticons/default/biggrin.gif)
"+drag +coefficient" found this old post: http://www.914world.com/bbs2/index.php?sho...ag++coefficient 0.38 for the 914-4 0.39 for the 911 turbo (IMG:style_emoticons/default/driving.gif) Andy (IMG:http://www.914world.com/bbs2/uploads/post-179-1147849221.jpg) |
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| flipb |
Nov 6 2009, 01:45 PM
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#5
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Senior Member Group: Members Posts: 1,728 Joined: 2-September 09 From: Fairfax, VA Member No.: 10,752 Region Association: MidAtlantic Region
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From linky link:
"It is interesting to note that, aerodynamically, the 914 displayed 20 percent less drag than the contemporary 911." |
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| SirAndy |
Nov 6 2009, 01:54 PM
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#6
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Resident German Group: Admin Posts: 41,676 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
QUOTE(flipb @ Nov 6 2009, 11:45 AM) From linky link: Btw. that book has some pretty substantial errors. (IMG:style_emoticons/default/dry.gif) But the crash pics are cool! (IMG:style_emoticons/default/w00t.gif) Andy |
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| marks914 |
Nov 6 2009, 02:03 PM
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#7
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Senior Member Group: Members Posts: 845 Joined: 9-October 04 From: the motor city Member No.: 2,912 Region Association: None |
Cd is only a number, what is more important is CdA
That is what really tells you how effective the aero is. Mark |
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| johannes |
Nov 6 2009, 02:25 PM
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#8
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Club Porsche 914 France President Group: Members Posts: 3,084 Joined: 13-January 06 From: France Member No.: 5,409 Region Association: France |
QUOTE(marks914 @ Nov 6 2009, 12:03 PM) Cd is only a number, what is more important is CdA That is what really tells you how effective the aero is. Mark |
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| astronomerdave |
Nov 6 2009, 02:33 PM
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#9
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Member Group: Members Posts: 69 Joined: 26-January 09 From: Los Angeles, CA Member No.: 9,979 Region Association: Southern California |
QUOTE(SirAndy @ Nov 6 2009, 11:44 AM) The search works! (IMG:style_emoticons/default/biggrin.gif) "+drag +coefficient" found this old post: (IMG:style_emoticons/default/pray.gif) DOH! In my haste I forgot the "+" and searching on "drag coefficient" by itself gave me mostly nonsense. thanks, --Dave |
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| ericread |
Nov 6 2009, 04:16 PM
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#10
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The Viper Blue 914 Group: Members Posts: 2,177 Joined: 7-December 07 From: Irvine, CA (The OC) Member No.: 8,432 Region Association: Southern California |
Here's two .pdf documents that should be of help...
2007_Drag_Coefficient_Poster.pdf ( 179.71k )
Number of downloads: 439
2008_Drag_Coefficient_Poster.pdf ( 276.51k )
Number of downloads: 335Eric Read |
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| astronomerdave |
Nov 6 2009, 04:38 PM
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#11
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Member Group: Members Posts: 69 Joined: 26-January 09 From: Los Angeles, CA Member No.: 9,979 Region Association: Southern California |
QUOTE(ericread @ Nov 6 2009, 02:16 PM) Here's two .pdf documents that should be of help...
2007_Drag_Coefficient_Poster.pdf ( 179.71k )
Number of downloads: 439
2008_Drag_Coefficient_Poster.pdf ( 276.51k )
Number of downloads: 335Eric Read Cool. That first poster is hard to read some of the numbers but I found the original source for it. Check it out here: Chris' 914 Porsche Aerodynamic Aids |
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| ericread |
Nov 6 2009, 04:40 PM
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#12
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The Viper Blue 914 Group: Members Posts: 2,177 Joined: 7-December 07 From: Irvine, CA (The OC) Member No.: 8,432 Region Association: Southern California |
QUOTE(astronomerdave @ Nov 6 2009, 02:38 PM) QUOTE(ericread @ Nov 6 2009, 02:16 PM) Here's two .pdf documents that should be of help...
2007_Drag_Coefficient_Poster.pdf ( 179.71k )
Number of downloads: 439
2008_Drag_Coefficient_Poster.pdf ( 276.51k )
Number of downloads: 335Eric Read Cool. That first poster is hard to read some of the numbers but I found the original source for it. Check it out here: Chris' 914 Porsche Aerodynamic Aids Thank you for posting the original source. I downloaded it but I couldn't remember from where I downloaded it. I hope it helps! Eric |
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| ewdysar |
Jun 20 2010, 11:41 AM
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#13
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What happens here, stays here. Group: Members Posts: 558 Joined: 29-October 04 From: Altadena, CA Member No.: 3,030 |
QUOTE(marks914 @ Nov 6 2009, 01:03 PM) Cd is only a number, what is more important is CdA That is what really tells you how effective the aero is. Mark I hate to resurrect and old thread, but after more than an hour of searching, it looks like this info just doesn't exist. Does anyone know the CdA of a 914, or alternatively the frontal area of a 914 so that I can do the math? Thanks, Eric |
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| Al Meredith |
Jun 20 2010, 12:09 PM
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#14
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Senior Member Group: Members Posts: 960 Joined: 4-November 04 From: Atlanta, ga Member No.: 3,061 |
Porsche Panorama May 1978 page 27 figure 14. I can scan if you all want me to but, the numbers are as follows:
Lamps closed , windows closed ,roof on Cd= .363 lamps open, windows closed, roof on Cd= .380 lamps closed, windows open, roof on Cd= .381 lamps closed, windows closed, roof off Cd= .389 lamps closed, windows open, roof off Cd= .447 lamps open, windows open, foor off Cd= .464 |
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| ewdysar |
Jun 20 2010, 02:43 PM
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#15
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What happens here, stays here. Group: Members Posts: 558 Joined: 29-October 04 From: Altadena, CA Member No.: 3,030 |
QUOTE(Al Meredith @ Jun 20 2010, 11:09 AM) Porsche Panorama May 1978 page 27 figure 14. I can scan if you all want me to but, the numbers are as follows: Lamps closed , windows closed ,roof on Cd= .363 lamps open, windows closed, roof on Cd= .380 lamps closed, windows open, roof on Cd= .381 lamps closed, windows closed, roof off Cd= .389 lamps closed, windows open, roof off Cd= .447 lamps open, windows open, foor off Cd= .464 Thanks for the info, but I'm looking for the CdA, not the Cd. The various permutations of the Cd are easily found. As Marks914 aptly stated "Cd is only a number, what is more important is CdA. That is what really tells you how effective the aero is." The CdA is merely the frontal area of a car (object) multiplied by its Cd. I have yet to find either the frontal area or the CdA. The Cd of a 911 (0.32) is less than a 914, but the 914 is reported to be "slipperier" due to its lessened frontal area. Thanks again. |
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| jmill |
Jun 20 2010, 03:58 PM
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#16
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Green Hornet Group: Members Posts: 2,449 Joined: 9-May 08 From: Racine, Wisconsin Member No.: 9,038 Region Association: Upper MidWest |
QUOTE(Al Meredith @ Jun 20 2010, 01:09 PM) Porsche Panorama May 1978 page 27 figure 14. I can scan if you all want me to but, the numbers are as follows: Lamps closed , windows closed ,roof on Cd= .363 lamps open, windows closed, roof on Cd= .380 lamps closed, windows open, roof on Cd= .381 lamps closed, windows closed, roof off Cd= .389 lamps closed, windows open, roof off Cd= .447 lamps open, windows open, foor off Cd= .464 (IMG:style_emoticons/default/happy11.gif) Attached image(s) 
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| jcb29 |
Jun 20 2010, 08:56 PM
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#17
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Member Group: Members Posts: 89 Joined: 29-August 04 From: Clovis, CA Member No.: 2,646 Region Association: Central California |
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| ewdysar |
Jun 20 2010, 09:44 PM
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#18
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What happens here, stays here. Group: Members Posts: 558 Joined: 29-October 04 From: Altadena, CA Member No.: 3,030 |
QUOTE(jcb29 @ Jun 20 2010, 07:56 PM) Yep, I've read that site and all of its attachments is great detail. There are many figures provided with a lot of relative differences between various configurations of a 914. However, while the formulas included reference frontal area, there are no values for area provided. So I'm still looking... does anyone know the CdA or the frontal area of a 914? Thanks, Eric |
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| type47 |
Jun 21 2010, 07:58 AM
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#19
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Viermeister Group: Members Posts: 4,254 Joined: 7-August 03 From: Vienna, VA Member No.: 994 Region Association: MidAtlantic Region |
QUOTE(ewdysar @ Jun 20 2010, 09:41 AM) ..., or alternatively the frontal area of a 914 so that I can do the math? according to the technical data in the workshop manual, the height of the 914 is 1.23 m and the width is 1.65 m so I would think you could get a pretty good estimate of the frontal area if you assume it's a rectangle so you would get 2.03 sq m as the frontal area |
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| ewdysar |
Jun 21 2010, 09:51 AM
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#20
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What happens here, stays here. Group: Members Posts: 558 Joined: 29-October 04 From: Altadena, CA Member No.: 3,030 |
QUOTE(type47 @ Jun 21 2010, 06:58 AM) QUOTE(ewdysar @ Jun 20 2010, 09:41 AM) ..., or alternatively the frontal area of a 914 so that I can do the math? according to the technical data in the workshop manual, the height of the 914 is 1.23 m and the width is 1.65 m so I would think you could get a pretty good estimate of the frontal area if you assume it's a rectangle so you would get 2.03 sq m as the frontal area Unfortunately, this looks like a significant overestimation. As an example, an '86 911 Carrerra is spec'ed at 1.821 sq m (19.6 sq ft). Even the 928's were right around 1.95 sq m (21 sq ft). Still looking for the answer.... Thanks, Eric |
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