08-26-2019, 10:11 PM
|
#11 (permalink)
|
EcoModding Lurker
Join Date: Aug 2017
Location: Indiana
Posts: 14
Thanks: 9
Thanked 7 Times in 6 Posts
|
Quote:
Originally Posted by freebeard
The factory wind tunnels vary between themselves by a similar amount.
|
Thanks for the response.
I still find value in the coast down results. I can use those to compare the next one I do if I change something else on the car. If my speed is above 20 mph at the 70 second mark then I did something right.
|
|
|
Today
|
|
|
Other popular topics in this forum...
|
|
|
08-27-2019, 12:19 AM
|
#12 (permalink)
|
Master EcoModder
Join Date: Aug 2012
Location: northwest of normal
Posts: 28,687
Thanks: 8,143
Thanked 8,922 Times in 7,365 Posts
|
Agreed. Good for comparisons, but don't get official figure envy.
__________________
.
.Without freedom of speech we wouldn't know who all the idiots are. -- anonymous poster
____________________
.
.Three conspiracy theorists walk into a bar --You can't say that is a coincidence.
|
|
|
The Following User Says Thank You to freebeard For This Useful Post:
|
|
08-27-2019, 03:06 PM
|
#13 (permalink)
|
EcoModding Lurker
Join Date: Aug 2017
Location: Indiana
Posts: 14
Thanks: 9
Thanked 7 Times in 6 Posts
|
Quote:
Originally Posted by freebeard
Agreed. Good for comparisons, but don't get official figure envy.
|
If the variables at the bottom of the speadsheet is changed, shouldn't the CD and CRR numbers change also?
|
|
|
The Following User Says Thank You to modified metro For This Useful Post:
|
|
08-27-2019, 03:18 PM
|
#14 (permalink)
|
Master EcoModder
Join Date: Aug 2012
Location: northwest of normal
Posts: 28,687
Thanks: 8,143
Thanked 8,922 Times in 7,365 Posts
|
I don't know. It would depend on the structure of the spreadsheet and the definitions of the variables.
__________________
.
.Without freedom of speech we wouldn't know who all the idiots are. -- anonymous poster
____________________
.
.Three conspiracy theorists walk into a bar --You can't say that is a coincidence.
|
|
|
08-28-2019, 11:59 AM
|
#15 (permalink)
|
Master EcoModder
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 16,306
Thanks: 24,436
Thanked 7,384 Times in 4,782 Posts
|
shouldn't
Quote:
Originally Posted by modified metro
If the variables at the bottom of the speadsheet is changed, shouldn't the CD and CRR numbers change also?
|
Since you're testing on a different day,the only way that you could isolate a difference,is to do back-to-back coastdowns,with and without the mods,so you'd always have a baseline reference from the same day/conditions to compare to.
You could have a dozen unaccounted for variables,any one of,which could affect your coastdown times.It would be impossible to sort it out.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
|
|
|
The Following User Says Thank You to aerohead For This Useful Post:
|
|
08-28-2019, 12:22 PM
|
#16 (permalink)
|
EcoModding Lurker
Join Date: Aug 2017
Location: Indiana
Posts: 14
Thanks: 9
Thanked 7 Times in 6 Posts
|
Quote:
Originally Posted by aerohead
Since you're testing on a different day,the only way that you could isolate a difference,is to do back-to-back coastdowns,with and without the mods,so you'd always have a baseline reference from the same day/conditions to compare to.
You could have a dozen unaccounted for variables,any one of,which could affect your coastdown times.It would be impossible to sort it out.
|
Thank you for the response.
I would totally agree with that. Not only environment changes but the possibility of things beings different on the car, tire air pressure, dragging brakes, wheel bearings, anything can make a difference.
__________________
|
|
|
The Following User Says Thank You to modified metro For This Useful Post:
|
|
01-07-2020, 08:50 AM
|
#17 (permalink)
|
EcoModding Lurker
Join Date: Dec 2019
Location: Switzerland
Posts: 53
Thanks: 8
Thanked 14 Times in 14 Posts
|
Hi everyone.
Can anybody share with me this SAE norm?
Actually I have used the Excel sheet to calculate my values also, but I am not satisfied with the sheet as I find the math in here too basic.
I have done a prototype version of a version (on Scilab) with least square adjustment that would be able to give a more robust answer, with least square adjustment.
At the time, I get 0.590m2 as a CdA for my car, with an estimated accuracy of +/-0.037m2 (1sigma). I did only 4 runs, 2 in each direction.
I am planning to integrate in the model some different values, including slope (this would allow to do the testing on a non-flat road) and wind speed relative to the car direction.
I am happy to share with you the results, and would be happy to get some raw data from you to test on the algorythm.
Best Regards
__________________
|
|
|
|