Keep in mind there are other tricks that can be used to keep flow attached to diffusors.
The diffusor I'm designing will have a center section about 20" wide that will be at an 18degree angle. The sides will be around 13degrees.
To see if the flow remains attached or not, I'll be using my cheap $10 spy video camera taped underneath the car, with the diffusor covered in tufts of yarn. If it doesn't, my plan is to add vortex generators at the diffusor leading edge.
Also, my center section is steeper to take advantage of my exhaust-activated downforce design. The outlet is a center exit design, with four small 1.5" diameter exhaust tips at a 10degree angle that will poke through the diffusor.
Now that my exhaust is almost finished (still refining the "quiet mode" sound), I can get to work on my diffusor. I need to get this 4' x 8' sheet of aluminum out of my garage :wink:
Finally, as a diffusor is kinda useless without a flat area just upstream of it to apply the reduced pressure to (the NSX engine/tranny compartment is just too open to be of any good), I will enclose that area. That will require some temperature-instrumented tests to ensure I won't overheat anything. More drastic mods (cutting out the trunk and venting above the tailights, etc) will be required later for, hopefully, my big power plans.
Dave
I don't have any good pics of the exhaust or the angle, but here is a video that you can get an idea of the configuration:
<iframe src="http://player.vimeo.com/video/18223839" width="400" height="300" frameborder="0"></iframe><p><a href="http://vimeo.com/18223839">New Loud Mode NSX Muffler</a> from <a href="http://vimeo.com/user1744194">Dave</a> on <a href="http://vimeo.com">Vimeo</a>.</p>
