The factory plastic undertray on the Evo is a pretty terrible design. It certainly does it’s job — protecting the underside of the motor from debris and assisting aerodynamics by limiting turbulence under the car — but the plastic screws holding it in place, the multi-piece design, and general flimsiness of the piece makes it a less than ideal design.

One option is to replace it with the APR splitter. This carbon fiber piece bolts to the Evo VIII bumper and extends all the way back to where the plastic undertray does. I used the APR splitter on my old Evo VIII, but decided to use the APR Evo IX Lip on this car so I had to come up with another choice.

Beatrush is a Japanese company that seems to specialize in racing parts. Their aluminum divider panel for the rear seat bulkhead is a pretty nice piece, and certainly saves you the headache of cutting your own panel if you decide to do what many of us do and mount a fuel cell in the trunk (a divider panel is required for safety reasons).

I found their undertray for sale on evolutionm.net, and decided that the Beatrush panel offered exactly what I wanted; a rigid, perfectly flat panel that mounted to the body with bolts and allowed for easy removal with or without removing the bumper. The dividers to route air to the brakes and the vents built into the panel are the extra touches that make purchasing the panel a better option than simply cutting a sheet of aluminum for myself. Sold.

You start by mounting these brackets on the factory fender liners. The extend the liner edge down low enough to bolt a flat panel to them, as well as being ventilated to allow for better air flow across the oil cooler.

Here is the bracket mounted on the fender. Note the hardware used and the fact that it butts up against the bumper edge.

Add the threaded clip to the under panel.

Bolt the support bracket just behind the tow hook.

The rear of the panel is attached to support brackets that fit between the tunnel brace and the bracket. You see the Cusco V1 and V2 braces in this pic, which replace the two black tubular metal bars on the stock Evo.

NOTE: Do not tighten the tunnel brace bolts completely until after the panel is on, as you may need to shift them around to line everything up.

NOT PICTURED: Install the small S-shaped bracket to the intercooler center tab. This will secure the front of the panel.

Next step is to fit the air guides to the panel. The tabs fit through the slots cut in the panel and are secured with bolts.

A shot of the guides installed.

The remaining pair of L-shaped metal brackets is used for the deflectors in front of the tires. Assemble the rubber to the brackets. Tighten from left to right to make sure that you don’t end up with a wave in the rubber flap.

Hang the panel on the car, secured loosely to the center bracket.

Secure the sides of the panel, with the hardware threaded through the diffusers you assembled earlier.

Next step is to attach the rear panel. Once the panel is bolted on, aligned to the front panel, and secured, tighten the transmission brace bolts.

The front panel is slotted where it mounts to the rear panel, allowing to set the alignment of the two parts. Note in this shot how there is only a small column of air routed towards the brakes.

Once the panels are bolted on, secure the access panel. The screws are kind of a pain in the butt to get started, but just take your time.

Use the factory plastic rivets to secure the bumper to the front panel. Check that all of the hardware is tight, and you’re ready to get out on the road!

UPDATE - February 16, 2007

I hate the black plastic rivets that secure the Beatrush panel to the front bumper (same as the stock under tray). They do not do a very good job of holding things together and they are difficult to remove. Once I added the APR front splitter to the car, things only got worse, as the holes didn’t line up perfectly any longer and fewer of the plastic rivets could be used to hold everything together. So, we came up with a more permanent solution.

We cut sheet aluminum to create a thin strip that we could use to overlap between the Beatrush panel and the APR splitter. It was then secured to the inside of the splitter.

We drilled holes in the aluminum that lined up with the holes in the splitter where the plastic rivets go. We then secured threaded inserts behind the opening. When the bumper is back on the car, bolts can then be passed through the Beatrush panel and screwed into the splitter. This is a much more stable and secure way for the under panel and bumper to be tied together.

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This entry was posted on Saturday, October 7th, 2006 at 10:59 pm and is filed under Installs & How-to's. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.