When I first bought my car in early 1998 it didn't have an OEM undertray. Instead it had a custom job that somebody fabbed up using thin sheet metal. It wasn't great and was clearly because they didn't want to pay for a new undertray after one of the incidents the car had been involved in. However in my opinion it wasn't much worse than stock so I continued to use it for many years. Then one day I had a little incident of my own that involved a curb and mismatched tires. After telling myself that a man wouldn't sit there and sob but instead bust his ass to make it better than before, that is what I did.

I have seen a lot of people talk about custom undertrays and various methods including carbon fiber. The point is because the stock undertray doesn't seal well and lets a lot of air pass around the radiator instead of through it. However I don't think a rigid material like carbon fiber is suitable. The main reason isn't because of the location or because it needs to flex while on the car. No, it is because during the install if you can bend the material you can close many more of those gaps without the use of lots of foam. Mine seals so well that even on the brightest days there isn't so much as a pinhole of light shining into the nose opening from the underside of the car. The sides of the undertray are touching the sides of the radiator or frame in most areas.

Though your results will vary depending on how adept you are with doing "stuff" I believe anybody can make one of these in about a day. Just follow these simple steps:

1. Collect the following materials: Large sheet of cardboard, ruler, magic marker, scissors, one large AC duct from Home Depot, something to cut the metal, some thicker metal for brackets, some screws, rivet gun (optional), and zip ties.

2. Remove the factory undertray.

3. Use the cardboard and create your design. Just a note here that I suggest going under the sway bar if you have the factory sway bar mounts.

4. Copy your design with your metal.

5. Attach new undertray to car.

So a few details. You will notice in my pictures that I have several hoses for the oil coolers. You will too and I bent the metal around them where I could. You can see this in the picture above. On the passenger's side I used a single small bracket. Seems like it would be insufficient but I never had a problem even at race speeds with the old undertray mounted like this and it was made from thinner metal. The hoses are protected from rubbing with simple hose cut and wrapped around it. On the driver's side I got a bit more fancy with a aluminum bracket. In the rear one side extends back and mounts to the frame via a zip tie. I would have used a bolt but the hole was stripped and I liked this just about as much. Notice the bends in the metal. This adds strength. Right below the radiator for this section there was about a 1/4" of space so I used some foam. You can see the foam popping just a bit next to the drain plug opening. On the other side I actually wrapped the metal up around the radiator and secured it with zip ties. In the front I bent the metal up so that it touches the bumper's opening. I secured it to the bumper with some metal wire.

Heat is this car's enemy and this mod will help a lot.