Cheap Aero and Free Horsepower

With the interior pretty well sorted out, it was time to upgrade some aero!

The first big ticket item I had on my to-do list… was the splitter. My original splitter has been a very trusty and durable steed. Made of ~9/16'“ plywood, it has seen A LOT of abuse. It’s also seen a lot of water, becoming waterlogged and starting to fail in many spots.

You can see 3 years of scraping and overall just not giving a shit if I hit something. Only about half of the fasteners were still doing their thing still. I used the OEM under tray points with M6 all-thread studs. Every time I pulled the splitter it was a huge pain to re-install. Lining up a bunch of semi-bent pieces of all-thread wasn’t easy. It’s also not the most aerodynamic design with a bunch of studs poking down 1.5” into the airflow.

It was time to re-design and build a better splitter.

What was left of the original splitter. Some of the wood around the splitter rods was rotting, and steel endplates were rusting (and steel, heavy), and overall the entire splitter was heavier than I remember… I’m pretty sure it’s soaked up a lot of water weight the last few years. It probably weighed close to 25 pounds. Into the burn pile it went!

So, I had a few options after some research. Drop $200 on a sheet of Alumalite (aluminum sheeting with a lightweight core) and cut to fit, or try to make my own from fiberglass. After researching building my own, I decided to give it a shot. The materials worked out to about $120 in my mind, so let’s burn a bunch of time to save $80!

I picked up two sheets of plasticore from the local hardware store. This stuff is what election signs are made of. This will be our core. I traced my old splitter with a few changes.

I used two sheets, overlapping them 90 degrees for added strength. You can glue this stuff with a hot glue gun.

I also wanted to make my splitter more efficient. I added some built in splitter diffusers. (Read more about basic DIY aero principles here) These fit between the wheel and frame rails, making the airflow here much more efficient. I chose a 10 degree pitch to the diffusers.

Here’s the finished core. It doesn’t need to be perfect, since we’re using chopped fiberglass matting to cover it up.

The tools of the trade. A gallon of resin and hardener, some mini rollers (don’t use foam, the resin will eat it up), and cheap paint brushes. I thought I’d use the gloves, but they became more of a nuisance than helpful.

I also bought a big roll of fiberglas chop matting from Amazon. It’s probably enough to make 5 splitters! A lifetime supply for me.

With the matting cut to rough size on the top of the splitter, it was time to add resin! I mixed up a bunch, poured it onto the matting and then worked it into the matting with the roller and brush. The biggest surprise… this stuff SOAKS up the resin. I used a lot more than I thought. If you use regular woven fiberglass cloth you’ll need A LOT less… but I can’t see it being strong enough with laying 3-4 layers vs one layer of chop matting.

Once it cured, the top looked decent enough. I added more around the exposed lip to strengthen it more since that’ll take most of the abuse on speedbumps and parking lot exits.

Now we needed to figure out a better way to mount this bastard. Having a look under the car and poking around the frame rails… a light bulb went off. There are some very robust, and heavy steel tie downs bolted to the frame rails. My assumption is these were used to tie the car down to the boat while it was shipped across the pacific back in 1993. With those taken off, I looked around the garage for something to use. Voila! The old uprights from one the GT wings I’ve destroyed! They’re stout, and aluminum (light weight). With a little drilling and trimming they fit nicely. Sometimes it pays to be a bit of a hoarder.

Using some aluminum angle, they will bolt up just right.

But, we need to bolt the angle through the splitter. I wanted to keep the bottom of the splitter as smooth as possible. So I devised a plate with studs to bolt though the splitter that will be integrated into the splitter.

Here’s the plate with the studs ready to be tacked up.

With the plate made, we could drill and test fit the mounting plates. They fit nicely, and now we can attach them to the bottom and finish it out.

The plate attached. Ready to lay the matting and resin.

Ta-da! The area around the plate was doubled up in matting.

With one layer done, I started cleaning up the leading edge area. Turns out, the matting is difficult to form a nice wrapping edge. When sanded and cleaned up, I had a bunch of holes in the splitter.

With the leading edge a bit of a mess, it was easiest to clean it up with a few layers of fiberglass fabric and resin.

On the frame rail, I added another mounting point for the splitter support bracket via a nut-sert.

Once I was satisfied with the splitter, I finished it the same way I finished my old one… with truck bedliner.

Now we’re ready to finish the top of the splitter.

More scrap carbon to the rescue! Cutting up the wing endplates I never used (remember I made my own) I had some cool winglets for the splitter. They’ll be mounted with some aluminum angle.

The splitter, ready for install!

Installed! Jesus my front bumper is rough. Anyways, the splitter was mounted in a few locations more than just the brackets we made. A few bolts into the fiberglass lip, and a couple into the rear underbody OEM locations with a better bolt system (NOT long all-thread, proper flathead bolts).

We needed to install new splitter rods too. The new splitter is more aggressive than my old one, it protrudes about 5” from the lip, my old one was only 4”. Splitter rods are definitely needed.

I also wanted to make the lip-to-splitter transition better. My old transition was just the splitter butted up to the lip. This probably wasn’t the most efficient, and likely let air through the crack. Armed with some garage door seal, I went to town. I know it doesn’t look that good yet, but I can clean it up, or go with a black plastic air dam.

Overall, my new splitter is almost half the weight of my old one. It’s not quite as strong, but I think it’ll hold up to track use. Was it worth it… in my honest opinion, not really. I have A LOT of time into this splitter, which in the end is just a consumable.

It cost more than expected too, about $200. So, I could’ve bought some 10mm alumalite, cut it to shape, and installed it in one afternoon most likely. But, I learned a lot, and the next version will be lighter, and more effective!

Moving on, we needed to build better wingstands! The ones that came with the NRG GT Wing are decent, but universal parts are rarely ideal. Mainly, if I mounted the wing just as it came, it sat way too upright for my liking. So, I modified the wingstands so they leaned back quite a bit more. Unfortunately, this gave me almost no adjustments to change the angle of attack. Typically, a good rule of thumb is 0 degrees up to 16 or so. Generally, after 14 degrees on a wing, air will stall and separate, which makes almost no downforce and ton a of drag. My wing was pretty much stuck at about 0 degrees. Good for drag, but we could probably get a lot more downforce if we had some adjustment.

So of course, we’re going to do more cardboard template work.

Here’s the original traced out. You can see I trimmed the bottom of it to lean the wingstand back more. It also required new mounting holes on the bottom.

With a little freehand, I figured out where I wanted to change things up. I’ll get a little more lean back on the stand, and more adjustment for Angle of Attack.

The original stands are pretty damn stout. I measured them and got 3/8” thick. They’re aluminum too, so weight isn’t too much of an issue. I ordered some 3/8” aluminum stock and was surprised when it showed up. It was THICC. I measured the old stands again… 5/16”. I’m dumb. It’ll cost me a bit more weight, but the new stands will be stronger.

I had no idea how I was going to cut the aluminum up. It’s a pretty intricate cut. I used to work for a contractor with a water-jet table… oh how that’d be handy right now. I asked a buddy with a plasma… but that probably couldn’t burn through that thicknessl. Then, I went to google. Some people had decent luck with oscillating jigsaws. I thought, why the hell not, a jigsaw is pretty cheap. $50 later, I was back from ACE Hardware with a saw and a bunch of metal blades.

The cutting took awhile. Go slow, turn down the saw speed (a trick for aluminum), and some cutting oil (or WD40) and eventually you’ll get there. After about an hour I had both pieces cut. Looking back on it, if I had access to a large bandsaw, that probably would’ve made quick work of it. Oh well, now I have a shiny new jigsaw for future projects.

Here are the rough cuts. I c-clamped them together and cleaned them up with a flapper disc on a grinder.

I have almost no fabrication training, I mostly make things up as I go along. I’m sure I could fabricate things like this MUCH faster with some training, and I think I will be signing up for a class through ETS Fab course soon to learn things the easy and correct way. (Check it out here: https://www.etsfab.com/)

Once they looked good, I drilled out the holes and gave them a test fit.

Dang, not bad! I also not had a good range of adjustment. I thought about leaving them in the raw aluminum finish, but soon realized I wanted a more finished look. Paint would probably not hold up to constant adjustments. So, I tried something new. Wrap!

A night in the kitchen, I’m not the best at wrapping (did I mention I’ve never done this?). A heat gun is HUGE in making this stuff fit where it needs to go.

Ta-Da! Flat black, you know my style.

Looking like it belongs!

Measuring the angle of the chord, we have 3 adjustments, 3 degrees, 10 degrees, and 14 degrees. I will likely only use the 14 degree adjustment if I do a slow speed course like an autocross.

Moving along, onto the next little project. My MADPSI fenders are awesome. They fit well, and give me a ton of room to run very wide front tires/wheels if I wanted to. The 235s fit easily with some tuck. I imagine 255s would be easy, and even bigger if I ever needed it (I don’t think wider than a 255 is ever really needed on these cars)

But, where the fender ends and the bumper goes down, my front tire was exposed.

This is a huge No-No in the aero department. The tire poke causes a huge drag in aerodynamics, affecting the entire airflow over the car.

MadPSI did have a fix for this. They included some cool bumper add on pieces to help hide the front tire poke.

Initially they look pretty decent. But the more I dug into finishing and mounting them, the more difficult it would’ve become. They had no way to attach to the bumper, I thought about some sort of stud system and drilling holes into the bumper. The add on also only went down to the bottom of the bumper, leaving my lip exposed. So I’d have to build another add on from scratch to cover that portion. And lastly, they didn’t fully cover the tire! Thinking about how much work these would be to finish, I decided to go with a much simpler solution.

More CAD! I bought a small sheet of black plastic HDPE sheeting off amazon (1/8” thickness).

Using my fancy new jigsaw, this stuff cuts like a hot knife through ice cream. You can clean up the cuts easily with a grinder/flappy disc too.

Mounted it to the bumper lip with simple screws. It’s very stout and should really help with my drag issues.

The best part, this was very cheap (like $20 and I have a ton of sheeting leftover for other projects) and only took about 30 minutes to build and install both sides.

The tire poke is pretty much completely covered now, boo yah.

That’s about it in the aero department for this installment of the Apex Chronicles. But, we do have a mod to make some more POWAHHHH.

Recently Alex Wilhelm discovered a free 5whp on his 2gr swap by porting out the lower intake manifold. Basically a free mod if you have the tools (which I do, the man who dies with the most tools wins) to grind away some aluminum.

Check out his findings here: https://wilhelmraceworks.com/blog/2gr-power-gains
So, I pulled my lower intake manifold and starting hacking away.

Since the injectors seal from above with an O-ring, you can basically eliminate the entire injector boss and smooth out all the casting.

A dremel and air powered cutting tool help. Don’t forget a carbide cutting bit. It’ll clog with aluminum, but if you grind on some scrap steel it will clean itself out. Also, I highly recommend wearing a dustmask when doing this. It create a lot of aluminum dust, and last I checked, we breath oxygen, not aluminum.

See, it makes a big mess! There’s more material to remove than you think.

Once it was all ground out, I decided to hit it with those little dremel polishing pads and the thimble of compound they give you. To be honest, I was surprised at the results… it came out pretty nice! Once done, I THOROUGHLY cleaned the manifold with water and air and more air and then re-installed. She fired right up, so I didn’t make things worse!

Stay tuned, next month we dive even deeper into the winter revival.