Join Date: Mar 2006
Location: Southern California
Exige - front under tray aero panel project
I have wanted to improve the aero of my Exige for some time and have been evaluating aftermarket solutions. However, I cannot reduce the front clearance by lowering the car or installing a full splitter because my car just barely makes it into and out of my driveway (and scrapes if my line of approach is off by less than one foot).
So, I fabricated a solution that is a functional compromise: a flat panel that seals the cavity under the backside of the OEM air dam and extends back to fill in the chassis gaps at the front wheel wells. It flattens the entire front underside and modestly expands the "real estate" at the front wheel wells for air to smoothly travel over toward the rear of the car.
I made a template of cardboard using the OEM air dam bottom edge and the OEM aluminum service panel as guides for shapes and fastener locations. I trial fitted the cardboard template several times to finesse design and fit, and then I cut out the aero panel using 1/8 inch ABS plastic ($50 for a 4 x 8 ft. sheet sourced locally here in SoCal). An assortment of screws, nylon spacers, speed nuts and nylox nuts cost me about $15.
The aero panel tucks into the full width of the OEM air dam about 1/2 inch, extends back to cover the same area as the OEM aluminum service panel, and has two extensions that cover the chassis openings at the front wheel wells.
I installed the aero panel with the smooth (shiny) side facing the air flow / ground. The aero panel piggybacks on the OEM aluminum service panel and attaches through the OEM service panel into the OEM attachment points. The aero panel's wheel well extensions are fastened in place with screws and speed nuts that clamp against frame flanges on both sides of the chassis wheel well openings. For two areas of the clam underside and OEM service panel where height differences exist for attachment points, I used 1/4 inch thick nylon spacers held in place on the screws with circlips. The circlips serve to retain the spacer on the screws while installing and removing the aero panel.
Fitment of the aero panel is the same as the OEM service panel but with two extra steps: position the aero panel into place into the OEM air dam and ahead of the front clam at the wheel wells; attach the clips that fix the aero panel extensions at the wheel wells (easy to do with wheels in place once the aero panel is finished and clips are fitted).
Because the 1/8 inch thick aero panel adds extra stiffness to the front underside...which I don't consider to be a good thing, I intend to swap the metal fasteners for plastic ones as a precaution to avoid compounding damage to the front crash structure and clam in the event of a low speed bump.
I took the car out on a test drive today and drove a familiar route at speeds of 55 to 75 mph, including several high speed sweepers, and with short bursts up to 90 mph. While I am no engineer and did not take any before and after measurements using aero instruments, the front end felt more planted as speeds increased and it felt like the front tires had much better bite in corners. This test drive was using Toyo T1Rs that I run on the street, and air temps were significantly cooler than the last several times I drove the same route (55 degrees compared to 75-90 degrees, which means the tire rubber should have less grip than when ambient temperature is 20-40 degrees hotter).
The real test of any aero benefit of my aero panel would be on a high speed sweeper such as Riverside at Buttonwillow or the Roval banked turns at Auto Club Speedway...hopefully soon!
Satisfied that front aero has been improved, I plan to close the gaps around the rear wheel wells by installing Really Light Stuff's rear Undertray Aero Kit. The Undertray Aero Kit's two piece (per side) design looks well thought out for easy removal and installation of the diffuser and engine service panel, and it will clean airflow around the rear wheel wells and to the diffuser. My car runs a BOE Silent Touch exiting above the diffuser, and I already fabricated an aluminum fill panel for the diffuser to clean up the OEM diffuser.
2006 Exige - Phantom Black / Touring Pak / Track Pak / Limited Slip Differential / Traction Control / Star Shield
Last edited by Lotusmotion; 12-30-2012 at 05:08 PM.