DIY Splitter for Autocross and Track use
Want to make an effective DIY splitter that is a composite material, easy to work with, cheap and durable? If you answered yes then you have come to the right place. After a lot of internet searches, reading track forums and talking to people at the track I decided to go with the tried and true birch 15/32nd’s composite splitter material. Also known as plywood. Before you laugh away this article consider the following items in support of a birch composite splitter:
Why make a DIY splitter from birch plywood?
- Ligher than 1/8″ aluminium plate. My piece of Birch weighed in at 1.22 lbs per square foot. 1/8″ aluminum plate weighs 1.78 lbs per square foot. In other words, the 1/8″ aluminum plate is 46% heavier than a 15/32 birch splitter.
- Cheap. A 4’x8′ piece is $35-40 from “home depot racing.”
- Easy to work with. I used a jig saw and skill saw to cut it to shape.
- Durable. I’ve hit lots of cones, scraped driveways and even hit a parking curb. It still looks good and is fully functional.
- Strong and stiff. Despite a 4.5″ lip I did not need strut rods and have tested it at speeds of 130 mph.
Making a template
I wanted my splitter to follow the contour of my 1968 Camaro and look good. I also wanted it to extend all the way back to the cross member and control arms to keep as much air out of the engine compartment as possible. On a modern car you can usually trace a partern out using the front air dam. For my 68 Camaro, I removed the front bumper and traced the outline onto cardboard. I then measured the width of the car and finished off the side shape with a straight edge. If you look closely at the bumper outline in the below pic (above the ruler) you can see where I shifted from the bumper outline to the desired width. Because I compete in the SCCA CAM autocross class I couldn’t have the splitter protrude beyond the perimeter of the body.
Finished cutting out of cardboard
Test fitting the cardboard template.
Cutting the splitter from plywood
Once you have the cardboard template where you want it, simply trace the outline onto the plywood. One thing I’m glad I thought of was to go back over all the straight lines and retrace them with a straight edge. Further, I cut all straight lines with a skill saw as it gives a superior edge. I used the jig saw for the curved sections.
All cuts finished
Finally, I used general purpose primer and semi gloss black paint from a spray can to finish up the splitter. The average enthusiast can’t tell that its a plywood splitter. In addition to being bolted to my super strong Spectre Performance front spoiler I added 5 additional mounts made from 1″ 1/8″ aluminum strips that I bent into brackets. I used the bumper mounting points and roll bar mounting points on the frame for four of the brackets. And for the fifth bracket, I tied it into the center valence bracket to radiator core support.
10 thoughts on “DIY Splitter for Autocross and Track use”
can we see pictures of the support bracketry? Overall this is a solid DIY!
Thanks Phil. I will get some pics of the brackets this weekend and add them. I took pics of the brackets when building the splitter but they went MIA.
Phil. Here is a pic showing two of the brackets with the splitter remove. The majority of the weight created by the down force is supported by the front chin spoiler. These brackets don’t take much weight and at high speed should be resisting compression from the spoiler rather than holding much weight. https://www.autoxandtrack.com/diy-splitter-1968-camaro-support-brackets/
Excellent article. Thanks for taking the time to document and share. -V
Can this be done with abs plastic at 1/4″?
Hi Timothy, I wouldn’t recommend ABS plastic. The weight to strength ratio of ABS isn’t very good. I have a few friends that have tried ABS. As an undertray to seal off behind an air dam it can do okay. As a splitter I’ve yet to see one that doesn’t deform at high speeds. If you have a small enough lip it might work out fine.
looking at getting something similar done to the car this winter. I’m just wondering about aero gains at low speeds…
is there any noticeable difference on an auto x course? I understand at higher speeds on a road course this will be a whole lot more effective, just wonder if the weight of the splitter is worth it for the aero gains on an auto x course? on that note, I notice you don’t run a taller rear spoiler like I have seen on other prepared auto x cars, what’s you opinion on their advantage/disadvantage?
If I’m being honest I couldn’t tell a big difference on autocross or the road course. But I never did any A B A back to back testing with my splitter. Something I still want to do. Testing a larger rear spoiler is still on the todo list! Probably another thing that will be subtle and hard to feel.
Chad, I have the same Spectre front air dam. After the past couple years have you come to see this as worth it? Do you still run it? It didn’t look like it in your most recent video from Willow Springs. Thanks!
I haven’t run it recently as I damaged it and need to repair it. I do plan to run it again but I can’t say that I could tell a difference from seat of the pants feel. It would be great to test it at LVMS as I have a lot of laps there without it.