Addressing the Gas Fumes
Our first priority after all the gas fumes was to figure out what had happened. We dropped the fuel tank and started checking things out. This is a familiar sight for most people that have tracked a 240SX, the tank inner baffling broken loose. We found that this had bounced around and pulled off the vent tube internally. We thought maybe the vent hanging down in the gas might have caused it to push gas out of the tube during cornering. And maybe once enough gas was in the tube, the tank wasn't venting properly and pushed out of the cap? It didn't quite make sense, but at least was a direction.
It's never fun getting this baffle out of the tank, it usually involves mangling it with pliers until it fits out the hole.
We also hooked up a check valve and two small fuel filters to try to make sure fuel was not able to make it out of our vent.
While we had the tank out, we discovered some soot marks on the tank, and tracked down that our muffler was leaking. It wasn't quite this open until we started cutting, but the hot exhaust on our gas tank was building pressure faster than the vent was releasing, which opened the safety valve in the gas cap. The combination of raw gas making it out as well as the constant venting of vapors was what made our last race so horrible.
You can see the top of the muffler was letting go as well.
This is what we picked up to replace it.
We also put some heat shielding on the gas tank, all of these together should solve our issue!
Aerodynamics
Next up to make our car faster was to take care of my wing jealousy. Adding some kind of aerodynamics to the car had been on the "To-do" list ever since the very first race.. but we were finally doing it. My goal was to generate as much efficient downforce as I could with a very limited budget. Wanting to avoid drag scratched a spoiler, and while I looked very long and hard at getting a profile cut from foam and laying fiberglass on it myself, I just didn't have the time. I found some decent reviews of the "NRG" style carbon fiber 3d wing. It looked like an OK profile and people were saying that with just the wing they were getting high speed understeer, so I figured it must be doing something. I really wanted it to be mounted strong enough that I could move the car around by the wing and it not be flexing around.
I decided to try mount to the chassis, and the logical point was through the bolts in the rear frame rails that hold the rear bumper.
I took the aluminum bumper from our engine donor Maxima and hacked it in half to use as the vertical supports. Then I made some steel plates that would pass through the trunk. To try get some clean air, we mounted the wing about the same height as the roof.
While this isn't all bolted together, you can see the bracket going down into the frame rail as well as the small bracket going back to the tail light area.
The next thing I was trying to work out was how to cut the little slices in the trunk at precisely the right spot. I couldn't put the trunk on with the brackets on, and I didn't want to have any more cut than I had to. This is where Nathan came up with a brilliant idea to use a laser projector.
I lined up the line exactly with the bracket while it was bolted in, then took the bracket off, laid the trunk on it, and the laser line was exactly where I needed to cut the trunk!
We opened them up until we could slide the trunk on, and there it is!
However after some tugging on the wing supports, there was still just a little bit of flexing. I put together a little aluminum structure tying into the strut towers, and now I could pull the car around without seeing any flexing.
These kinds of pictures can be hard to find online, so here is the profile of the NRG wing. The trailing edge is pretty blunt, but this is an OK wing shape. There is a pretty drastic difference in the middle and ends for Angle of Attack, but they don't make a constant chord version of the wing so I'll live with it. If I set the middle to a pretty reasonable angle the ends are likely not stalling.
The end plates that the wing comes with are small and incredibly thick. I picked up some carbon fiber sheet to make my own.
After reading around for a few hours, I settled on this shape. The most important piece is that they extend down further than the originals, and are larger which should help the wing be a little more efficient and make more downforce.
I really like how it came out, and it looks like it should do something!
Now if I didn't want to understeer like crazy.. the next step was to try balance it out. I picked up some 3/8" birch plywood and we cut out a rough shape.
We tried to extend as far back as we could, which ended up making sense to end at the subframe for mounting.
We also discovered that our sway bar and oil pan were a bit too low for the height we wanted to run the splitter.
We built an aluminum frame to attach to the frame rails as well as the subframe.
Again using an aluminum bumper from the engine-donor Maxima, we made some brackets for supporting the splitter. You can also kind of see that we used a router to round the edge of the splitter.
Bumper brackets with supports finished.
I had also read to treat a splitter as a consumable, so we made a second copy and primered them both.
After painting black and attaching our brackets, it was getting close.
We mounted it on the car and it had no problem supporting the weight of one Nathan! After this we added some plastic to the front to seal off the area between the bumper and the splitter.
Our swap bar we had previously relocated with brackets, but that rotated it down and in the way. To get around this, we bought the Sikky sway bar, which has plenty of clearance for the engine in the factory position.
Here are some shots of the car ready to rock!
