--- My New Metal Rear Underbody Diffuser ---
 

So, I just finished 15 minutes ago, with a cut finger :D

Made of 30 gauge sheet metal (Would have probably done 26 gauge if I were to do it again), the total cost was of $35.12. The sides are flush with the tire (actually, a little more "inwards"), the pictures make it show in some angles as it would be extruding past the tire and rim, but it does not.

I painted the top and sides black (with spray paint, and two coats of clear) so that it would look a little more like all those exotic cars carbon diffusers ... :) Ok I tried I tried ...

I still have to do the middle, but that will be tomorrow as its dark now. But I am VERY happy with the results so far. It is going to be FAR superior to the little dinky things of coroplast that I had on there before. Haven't gone on the freeway yet but the rivets should hold everything in place and everything should be good to go.

(Pictures are from phone, sorry!)
http://i427.photobucket.com/albums/p...010709_006.jpg

http://i427.photobucket.com/albums/p...010709_007.jpg

http://i427.photobucket.com/albums/p...010709_010.jpg

http://i427.photobucket.com/albums/p...010709_008.jpg

http://i427.photobucket.com/albums/p...010709_009.jpg

http://i427.photobucket.com/albums/p...010709_003.jpg

http://i427.photobucket.com/albums/p...010709_005.jpg

http://i427.photobucket.com/albums/p...010709_004.jpg

Wow, you car looks......normal.
Nothing like my rear-wheel-skirted, grille-blocked, side-mirror-deleted coroplast-gorillatape car.

That's my number one objective with this car; yet it has a grill block, front tire deflectors, front underbody diffuser, vortex generators, ALL LED lights, etc etc etc.

I want for people to think green in a way that many don't, which is that any car can be "green" while being "normal" or good and sporty looking :)

I like it. I'm in Sulfuric's camp: Coroplast and Gorilla tape. But my wife wants nothing to do with appearance-altering mods. You present a good compromise!
Do you have a Scangauge to verify results?

Looks like you should pull in the sides

basslover911 -

I think winkosmosis is right, but I still like it. It makes me think of the Prius.

CarloSW2

diffuser
 

What is it's angle with respect to the ground? And do you have a bellypan leading up to it?

The ones behind the tires (the ones on the pictures) are not steep at all, probably around 3 degrees.

The middle one (which is finished now) is more like 7 degrees or so.

Also, I don't have a complete belly pan yet (I have the oem one in front but nothing in the middle of the car yet). I am going to see how durable this diffuser is and if everything works good I will make the middle one in about two months or so (Since that one is bigger and is going to be a little more, probably around $40 or so).

In regard to the sides, I wanted them as close to the edge of the tire as possible as to catch all the air coming out of the spokes of the wheel and try to straighten it out a little before going into the wake.

Nice !

Functional, yet 'cool' to the uninitiated. 'thumbsup'

I'm a little concerened about pedestrians and children. If they brush up next to your car, will they get cut ?