Designing a partial kammback on a sedan - Page 4 - Fuel Economy, Hypermiling, EcoModding News and Forum

Weather Spotter · 09-08-2010, 12:33 PM

looks good to me!

wagonman76 · 09-09-2010, 01:36 AM

http://ecomodder.com/forum/showthrea...ad-3292-4.html

Aeromodder - that short little kamm looks a lot like the solid part of my tail that is directly behind the rear window. I did a little experimenting this summer. Oh last year I actually lost FE when I extended the tail farther like the last page of my build thread. Earlier I used a cheap plastic ($5) and it lasted 2 weeks. I feared mpg would tank due to the open parachute, but it didn't really affect it much at all but the year was still early and cold. Then I replaced it, and we had more sun this summer than I've seen in 20 years. The UV killed the plastic by July 4 and I started losing panels, but not FE. Then they all fell off and still the FE was about the same. Then a few weeks ago I decided to cut the extension off (can easily weld it back on if needed) and try it with the Prius/Aztek look. Still about the same. I added plastic after that but still about the same. So I'm guessing that just about all of the FE gain comes from that little solid part right behind the rear window like you see on page 3 of the build thread. I need to get some pics, I've not been on the computer much lately.

AeroModder · 09-09-2010, 01:15 PM

Thanks for the tips. I'll be pulling my kamm off to see if there's any difference without it, and see if it's worth the loss of the use of the trunk.

Weather Spotter · 09-09-2010, 02:07 PM

Do some ABA tests please!

Ps: The wiki needs to be feed more data to stay alive

ha ha

AeroModder · 09-09-2010, 09:10 PM

I don't have the instrumentation for ABA testing, unfortunately. I'm stuck with tank averages. When I fill up my tank, I'll rip off my current partial kamm and go back to the notchback, and see if there's any measureable difference. I don't have the funds for the materials to build the full kamm yet.

Weather Spotter · 09-09-2010, 09:18 PM

Tank to tank data is very usable, if the route is similar and the weather is similar.

I take any data I can get, add it to the wiki, note how it was gotten, and let the end users decide for them selves how valid it is.

Another test you can do is coast down, with aero mods this can show differences better than tank to tank. Find a good road and have fun!

AeroModder · 09-10-2010, 12:53 AM

My usual coastdown testing involves noting speeds at set distances (road signs). I've noticed that after a certain point in the modding, there was little to no difference, since the coast starts at 45 MPH. Even then, it's varied by traffic, wind, temparature, and vehicle load. I've got some average data down, and I'll see if there are any differences.