New undertray design
 

After finally getting around to building my undertray, I got the two middle panels in. My biggest problem was space underneath the car, but I figured out a way to lift the jack higher.

Here are the two middle panels. you can see they're trimmed around the exhaust so it doesn't trap heat and/or fumes, or melt the coroplast.

http://i3.photobucket.com/albums/y93...Undertray2.jpg


Here's a picture of the front undertray I've had for a while.

http://i3.photobucket.com/albums/y93...tundertray.jpg

There was a definite reduction in wind noise, as well as a jump in economy. My estimate is a 5 MPG gain on the highway. My daily 40-mile commute used 2/3 as much fuel than before.

Photos of the rear panel of the undertray to come, when it's finished. I'm still working on the diffuser fins.

Looks awesome, great job!!

Thanks!

Here's the final touches on the rear diffuser and undertray panels:

http://i3.photobucket.com/albums/y93...usercorner.jpg

http://i3.photobucket.com/albums/y93...ertrayrear.jpg

http://i3.photobucket.com/albums/y93.../Diffuser1.jpg

I left an inch of coroplast off of the end of the bumper so the airflow separates cleanly. I put another panel on the side to seal off the open area under the trunk, and made sure to fold some of the material up so it doesn't have a parachute affect. The other side is open, though, since I need to leave the muffler in open air.

the rear verticle fins look like the ones one the fusion 999 flats racer, what specicly dop they do

They make sure the air moving through the diffuser stay straight and non-turbulent as the air pressure drops back to the ambient pressure.

Here's a thread from here on diffusers: http://ecomodder.com/forum/showthrea...read-8313.html

Nice

Now that I'm looking at it more.. I found out that the maximum angle of the diffuser is 25 degrees, which is far sharper than most. However, at slower speeds, I don't think this will make much of a difference. If I needed to, I could just add a few strips of coroplast between the diffuser and bumper as a spacer.

I could also put a smaller piece on the other side, but I'm concerned about the lack of mounting points on the open side. What do you guys think?

2.5 vs 25
 

I believe that would be 2.5-degrees,not 25.The panel can go as steep as 4-degrees,depending on where it begins under the car.It's in Hucho's book.

The edge of the diffuser is 25 degrees from the horizontal.

I actually don't have Hucho's book, but I've heard it referenced quite a bit. Now, is there a certain angle-per-length requirement before the airflow detaches, such as no more than a 4 degree increase per foot of panel lenght?

Now I'm curious. *scurries off to do more research*

Here's the figure from Hucho's book. Best angle is dependent on the aspect ratio of the diffuser (diffuser lenght/underbody lenght)

http://img72.imageshack.us/img72/4629/venturism8.jpg