I'm in the process of re-working my rear trunk lid. I felt it was too heavy and needed to be cleaned up.

Originally this was a AIR unit with about a 4" lip on the back. I changed it to have about a 8" lip which I made out of 1/8" wood covered with fiberglass and molded it in. I ran it for several years like this but now that I have changed the rear fenders to be removable I need to add about a 1/4" to one side to fill the fender to trunk gap. I've always through it was too heavy so I decided it was time to put it on a diet.

The part that was adding the weight was the inner supports ribs. They are the same size and shape as the ribs in a stock lip, but they are f/g. So the plan was to cut them off and add something simple and light. Once I began cutting the ribs out I found that they were not bonded very well to the lid. I could almost just pull them off with my hands. Overall I would say that this lid was a piece of crap when it left AIR. It also had one rear corner which was not inline with the other one but I fixed this years ago.

I used 1" PVC pipe that I split in two. You have to take sandpaper and rough up the surface to get the resin to stick to the PVC. The split pipe is flexible enough to bend and take the shape of the lid. You have to use clamps to tighten it down and hold it. Than you take 1" x 3" f/g mat strips and wrap it over the pipe. Once the strips cure you can remove the clamps. Than you can add f-glass the entire lenght of the pipe. It makes for a very strong support and lightweight! It takes several operations to get all the pipe ribs on there but it's done now. It is much lighter and actually stronger (stiffer).

I also plan on removing the f/g covered wood lip pieces. These pieces also added some unneeded weight as I had to use bondo to get it to look right. I currently have my oil cooler mounted in a cut out in the middle of the lip. I don't run the stock oil cooler on my engine, I only run the sandwich cooler. But now with a new RAT engine I going to change my thinking on oil coolers. I'm thinking I should run the stock cooler and delete the sandwich cooler. I only run autox's and I don't build up a lot of heat in the oil. The stock cooler will have constant air blowing through it from the fan. Also I can delete that heavy braided oil lines and block off plate and fittings. I've decided not to have a lip on the back at all. It is just going to be a stock looking lid. I don't think they really do anything anyway. OK they look cool but it too much work for no gain. I've done a little research and very few autox 914 run them. Here is a pic as it is currently...

Here is a shot of the PVC pipe stiffeners on the inside.

This is one side of the rear lip cut off and I'm started to fill in were the oil cooler was mounted.

The other side off.

F-glassing over it....

Next time you have an X-ray done of your lungs.. I want to see it..

Go baby! Carry on the 914 torch.


B

My garage has about a 1/16" layer of f/g and bondo dust on it.
I use a yard blower to clean it out.

B,
I decided to cut the lip off after what you said about the rear end only getting lite at +125 mph. I don't see that doing autox's. The Parade FTD winner this year didn't have a lip on his trunk, why should I?

Paul

Are you insane...? Your car will be the lightest moving object in the universe..................

SCCA GT2 only allows a 6 inch rear "lip" GT3 allows a 3inch..

All the rear lip does is "disturb" the air coming off the decklid and keep it from rolling up under the car at speed. A real wing would actually generate some downforce which *might* help you, but then you better have a FAT ASS splitter in the front to balance the car out. Most people cant drive past the car and get into "aero" territory. This is the area where the cars starts to lose grip and aero takes over and replants the car. Pro drivers speak of it often (when you are dealing with them on a regular basis) I personally have never experienced it, but plan on "looking" for it when we take the 993 out.


B

I know the lip just cleans up the airflow and reduces drag but doesn't really add down force. That 'd take a wing and I not in that speed range ever doing autox's.

And I not so sure a wing is allowed in SCCA solo II on a mod car like mine.

If you add the weight of the lid I cut off, the sandwich cooler, braided lines filled with oil and block off hardware and add the stock cooler back on, I still saved +10 pounds I's say.

All in all, a good decision.

Paul

wow-
that represents a lot of hours! Looks really good. Fiberglass work is really messy too. The pvc replacement ribs are a great idea. What did the others look like that you yanked out? How much weight do you think you save over stock?

QUOTE (SGB @ Jul 17 2005, 06:56 PM)

wow- that represents a lot of hours!  Looks really good.  Fiberglass work is really messy too.  The pvc replacement ribs are a great idea.  What did the others look like that you yanked out?  How much weight do you think you save over stock?

The other ribs were the same size and looked just like a stock hood.

How much have I saved over a stock steel lid?

A stock lid weighs 35 pounds. Mine will now be 5-7 pounds

Paul