Im about to be starting a prototype for a rear diffuser for the GT's in the next week or so. It will be a trim to fit application with 3 main veins and enclosing the bottom of the the exhaust tunnels on the rear bumper. Needing some feedback from Ppl. will enclosing the bottom of the cradle impede heat displacement. if so can 3 1" ports channeling air under the car into the engine bay compensate for it or should the ports be larger? This will be a ram air effect when the car is in motion. This diffuser will start at the front of the cradle and carry to the rear bumper, tieing the bottom of the rear bumper to the cradle. Heat generated by the exhaust will be taken care of by pipe wrapping and aerospace padding bonded to the diffuser in those areas. any feedback will be appreciated.

I read that rapping the pipe is not a good idea because of condensation and that ceramic coating inside and out is best. I don't believe one inch holes are a good idea. I would temporarily close the bottom area off with card board and check the temp. Just a guess but seems like the biggest problem would be when the car had just been drive and the heat would not be aloowed to rise as well up thru the vents.

If you start the diffuser at the front edge of the cradle, as you mentioned, then heat buildup in the engine bay shouldn't be an issue. There's a large gap between the front of the cradle and the firewall. That should allow plenty of airflow up and out the decklid grates.

Dealing with exhaust heat could be as simple as making the diffuser out of a heat-resistant material... like a sheet of aluminum. But some heat insulation wouldn't hurt, in any case.

I'll say go for it, just start the diffuser from the rear of the cradle. I'll be interested in the look and profile of the diffuser (which flow angle you'll be able to achieve) and how you're going to attach it to the rear bumper.

I do NOT want to railroad your idea into a ditch but since you are new here, I will give you a few pointers. First off, a lot of people on here do the old "Yeah, I'll buy one" and when the part is made and all the labor is done, they run for the hills......take it from me and some of the other vendors on here who have been screwed over. Build a kick-ass setup for yourself. Don't worry about production until your car is perfect. THEN if people want it, you can start talking price. Most people on here will want to pay very little other than being free.

As far as a diffuser goes, Honda S2000 diffusers range from $185 for aluminum to $800 for carbon fiber. They fit the Fiero perfectly under the trunk and have removable vanes for customizing. I don't know if you would want to buy one for yourself and tweak it with additional carbon fiber or fiberglass for the look/function that you want. You could be saving yourself a lot of headache by just buying one pre-manufactured.

Chris (Doublec4) on here installed this one on his car. You may want to do something similar and then work off of it:




These are $250 plus shipping on Ebay right now. They will require tweaking but again, it may save you some time from starting from scratch:

[This message has been edited by IMSA GT (edited 07-14-2013).]

I know the Bandwagon method all to well, all aboard until price is announced. As far as cost. Thermo forming a tough ABS wouldnt cost that much once a template is made. We have a thermo forming company about 30 miles from where i live. Ill play with the idea and talk to some of the guys at Thermoplate and see whats possible. I can build a bad ass defuiser and functional too and with a little time and effort adjustable too. First problem encountered was my rear facing sway bar.

quote Originally posted by dematrix86gt: I know the Bandwagon method all to well, all aboard until price is announced. As far as cost. Thermo forming a tough ABS wouldnt cost that much once a template is made. We have a thermo forming company about 30 miles from where i live. Ill play with the idea and talk to some of the guys at Thermoplate and see whats possible. I can build a bad ass defuiser and functional too and with a little time and effort adjustable too. First problem encountered was my rear facing sway bar.

Ah...that would be cool to make it from ABS. That really WOULD save cost in the long run.