Subaru Outback Kammback Experiment
 

Finally got enough coro lieing around to try this. I'm disappointed in the quality of pictures that turned out, my lens was smudged and I didnt realize it. As such, I only have one fairly lame picture of it, but you should get the idea.

http://lesbaru.com/stuff/kammback.jpg

Once again I apologize for my usual dark pictures, I pre-lightened this one up so people with dim monitors can see it.

It was just coro and duct tape, self supporting and suprisingly solid. Followed the lines of the car as best I could, although there was a crease on the top where the side met the roof. It rounded itself out more as it got further back though.

And as for the results....

Tested with scangauge, cruise set at 55 mph on a roughly flat, roughly straight 1 mile course (its hard to find anything like that in WV) down and back with no traffic. (Benefit of testing at night) Cruise was cancelled with the brake and then resumed. Weather was fairly calm, it was freezing though, winter gas. Blah blah. Sucky averages as a result.

Pretty much how I've tested everything else.

With The Kammback:
A 30.8
B 32.9
A 31.6
B 33.4
A 31.4
B 32.6
A 32.1
B 32.4

Average 32.15

Without the Kammback:

A 32.1
B 33.6
A 31.1
B 29.7
A 32.8
B 31.3
A 32.6
B 29.9

Average 31.63

So, just barely over half an MPG at 55 mph. Were this a free mod, it would stay, but a permanent solution would be costly, so its down on my list now. I encourage everyone to do their own testing and my post is just here as a reference for others. Blah blah.

As far as driveability, I didnt lose any rear view. I lost sight of the horizon behind me, but there were no blind spots created, which was actually pretty surprising to me. It also pretty much eliminated the need for the rear wiper. ;)

take the roof rack off and try it again? maybe the angle is too steep?

i'm surprised duct-tape held together so well.

I dont know, in person it didnt look steep enough. I'd say it was around 10 degrees. But what do I know?

As for the rack, thats staying. To take it off would involve disassembling the entire inside of the car and I'm still left with holes to fill somehow. AND I do use that thing at least twice a month now. Its fairly aerodynamic so without the crossbars it should be alright.

The angle should be no more than 15* from the steepest slope that it accompanies.

I'm honestly thinking that most of your airflow disruption will be coming from the relative height of your suspension, given that it's a Subaru and it's AWD. They're up there a bit.

I'm thinking an airdam will be more beneficial to you at first.

Interesting to see, even with the roof rack - would be a bigger gain for those of us with no racks I bet.
I agree, from the photos it looks steeper than 15 degrees, but a straight on side picture would settle the debate.
Matt

hm...maybe i should make a subee kammback just for old time's sake.

Can't see the pictures :(
lesbaru.com is not responding :(

i don\'t think this thread is breathing anymore.

I cant edit the original, so... FIXED

http://lesbaru.net/stuff/kammback.jpg

If I wasn\'t working 80 hours a week lately I would make another one of these.

very cool. thinking since i got my garage setup i\'m going to do some tricky stuff automobilically, speaking. i might have to try something like this. I\'d really like to make an aero trailer, though.

what do you do for 80 hrs a week?