Project SC300 Road Racer: Part 35 – The Wang Gang is Splitting Up
close up of tee nuts in bottom of splitter
Set the tee-nuts gently with a hammer.

The small prongs on the tee-nuts hold them to keep them from rotating as the bolt is tightened.


adjusting the mount on the splitter with a tape measure
Start with the mounts equidistant from the back edge of the splitter.

This ensures the mounts are square to the car (which assumes the car is square, but whatever)

Note that the mounts have slots. The slots give you a little adjustment fore-aft for the final splitter placement.


close up of aluminum mount sitting by itself
The Nine Lives Racing mount has slots in the top.

The upper slots allow you to adjust the height of the splitter somewhat, as well as its rake/angle.

Note that I messed up and didn’t properly explain to Nine Lives Racing about the hole’s location for the factory tow hook. As the design stands today, you cannot use the factory tow hook and the splitter mount simultaneously. This is because the mount blocks/covers the hole. I am working with them to rectify this. However, the mount does have a cut-out that goes around a stud that happens to be in the frame rail from the factory.


man holding small plastic aero piece on splitter in front of tire
Nine Lives Racing also sells these aerodynamic ramps that can be installed onto the splitter.

Morlind Engineering developed the ramps. Using them will increase exit flow from the splitter. Increasing the exit flow means more air goes under the splitter, which creates additional low pressure (downforce). The curved outer wall of the ramp generates a vortex for added low pressure under the ramp itself, which also increases downforce.

Ultimately you want to place the “scoop” inboard of the tire and as reasonably far back as possible. Cut the ramp’s core area out of the splitter with a jigsaw/skill saw, and then just screw the ramp into the splitter. There will be a follow-up article showing this process.

You also want the splitter (and the ramp) not to hit the tire. This picture shows clearly that the splitter has to move forward.

An extremely thorough race team would take the springs and swaybars off the car and move the wheel through the full range of motion (up/down and left/right) before locking in the splitter position. We guessed.


  1. Have you stood on the splitter to check for flexing, yet? That’s the ultimate test. You can’t imagine how much load these generate at high speed. Just imagine the force against a 1 sq/meter plank of wood during a hurricane 150mph!

    Wind Load Calculator

    Dynamic pressure (N/m2, Pa): 2940
    Wind Load (N): 2940=660lbs

    Also, I would argue that a flatbottom is the ideal aero solution for any car. Of course, it’s just a starting point because you want to attach strakes and flow diverters around the wheels to redirect turbulence.

    1. “Have you stood on the splitter to check for flexing, yet? ”

      No, and I probably wouldn’t. That’s not a realistic approximation of the load that the splitter experiences. It’s a point load. It’s a good test in the sense that if it doesn’t flex while experiencing an extremely unrealistic loading, it’s probably strong enough. But it’s not a realistic test.

      “Just imagine the force against a 1 sq/meter plank of wood during a hurricane 150mph!”
      Your load calculation is also quite off the mark, I think. A splitter does not receive load against its flat surface. It’s an airfoil, not a wall. That load calculation is for wind pressure hitting a flat surface straight on. It is not the load calculation of an airfoil’s lift force at 150MPH. If I had a full 3D scan of the car (Rob Lindsey, are you listening?) we could calculate the lift of the splitter to determine the amount of downforce it provides. For a simple, flat splitter with minimal rake and no additional aerodynamic aids (the current configuration) I do not believe I am going to be generating hundreds of pounds of force. Maybe 100-150. It’s a good question for Rob.

      “I would argue that a flatbottom is the ideal aero solution for any car. Of course, it’s just a starting point”
      This is a contradictory statement. If it’s the starting point, it’s not ideal. Ideal and best are nearly synonymous. It means there is no room for improvement.

      Is a flat bottom better than nothing / OEM bottom? Possibly. It would require testing.
      Is a flat bottom the best (ideal)? No. Additional aerodynamic devices will be better than a flat bottom.

      1. On the C5 Corvette CFD, with a similar size splitter, we saw a topside area/pressure of ~200in^2/2000pascals and an underside of ~350in^2/2500pascals. This ends up at roughly 200lbs at 150 mph but that load is distributed across a ~50″+ width.
        *Note that the addition of a splitter may well add more than that amount of downforce due to changing the overall flow structure. It impacts the amount of air going under the car and around the sides which can prevent lift in other areas of the car.

        Having said that, stiffness does matter (to prevent oscillations, damage, porpoising) so being able to stand on your splitter is useful, but it’s far from required.

        You can see similar results in the work on the 350Z we did for Grassroots:

      2. Well, of course, it’s not going to see 660lbs, that’s a worse case scenario if it was perpendicular to the flow stream, but I wouldn’t doubt that it would see a substantial amount of that load. I would probably guess somewhere around 300lbs at 150mph, because it’s at the stagnation point and the dynamic pressure is very high on the bumper. The air has nowhere to go, and is forced to change direction and that’s what makes a splitter so effective. Also, consider that the center of pressure is located about the midpoint of the splitter, so there’s a moment arm and a substantial amount of torque is being generated on the mounting point. Any amount of flex is going to open up gaps and make the splitter less effective when you need it.

        If you have some way of rigging up a whiffle tree, which allows the load to be distributed evenly over the splitter like they do with an airplane wing at Boeing, then I would absolutely love to see that data. But, I am assuming that you don’t have the time, money, or inclination to perform such a test, so the cheap and easy way is to stand on it and see if you can feel the flex with your toes.

        Regarding a flat bottom, yes, I admit that it’s a starting point, but it’s certainly a good one. In fact, considering how simple the geometry is, I can’t honestly see how anyone would argue against it. Sure, some trick double diffuser with meter long tunnels will be better, but that’s certainly not easy to make or install on a production car.

        The theory behind flat floors is really simple, a smooth surface is going to allow a fluid to flow faster than an extremely rough one. The higher velocity flow equates to lower pressure on the surface, and a lower pressure under the car equates to more downforce. This is all extremely well understood basic fluid mechanics.

        If you want a more detailed explanation, here’s a nice video with some CFD and actual data on a production car geometry:

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