Well i got bored at work today and decided to play around with making my own rear diffuser. I had given some thought to retrofitting an 06 model diffuser on, but dont really care for how it looks under the GC chassis(no offense to the 06+ guys). So here is what i ended up with. Constuctive criticism welcomed as i plan to make several more of these as work bores me.
its made out of 14gauge steel, i have almost finished making another one out of aluminum, but i dont think that it would withstand road conditions as well. i work at cherokee metals, we do all kinds of rolling, bending and fabricating metals. we are currently retrofitting every sonic in the country.
that looks promising, but I have some suggestions. In order for it to be more functional, it needs to be longer. Also, you should make the backing smooth without any sharp bends as that introduces turbulence which decreases the efficiency significantly.