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ncs 02-23-2009 03:20 PM

Project: "Except Buses" (WRX front undertray)
5 Attachment(s)
This project starts with the liberations of two street signs . . . . from a scrap yard. Turns out street signs get replaced fairly often and recycled. The result is cheap, large sheets of weatherproofed aluminum. Cost was about $37.

The goal was to make a skidplate/undertray. I used the factory undertray to locate the mounting holes. 3/4" square stock was cut to space the plate down far enough to line up with the bumper.

The wings are bolted to the main plate with 1/4" bolts. They are not very strong, so in the event of a collision, they'll probably shear off(a good thing). Also, bolting it together instead of welding took the 'ring' out of the plate.

About 3/4" of the leading edges has been hammer up at an angle for safety reasons.

I've only put about 35 miles on it so far. It does seem to be coasting further. No change in road or wind noise.

TomO 02-23-2009 03:44 PM

Very nice!

I wish I had access to the recycled street signs in MN.

MetroMPG 02-23-2009 04:46 PM


I added one of your pics inline with your post. Hope you don't mind.

IheartGeos 03-04-2009 11:08 AM

Very nice!
That is a very nice looking mod! How hard do you suppose it will be to put it on / take it off for maintenance?

I have been thinking of what to build an underbelly pan out of for my Geo, I will have to see if I can get recycled signs here in Nebraska, they are very sturdy and light!

ncs 03-04-2009 02:42 PM

I used the five bolt holes used by the factory plastic undertray. Asside from the weight, it's just as easy to remove as the stock piece. I have found a problem though. If I drop something in the engine bay, it no longer falls out the bottom.

Coasting distance increased enough to screw up my stop light timing. Also, cruising load dropped a whole .01MPa.

Nden 03-04-2009 02:50 PM

sweet! do they carry them sheets at HomeCHeapo or Slowes ?

JV-Tuga 03-04-2009 10:06 PM

since it doesn't go from front to back how significant is the difference, if any?

ncs 12-15-2010 10:44 PM

Round Two
Turns out there are some factor undertray aero parts for the sti of the same year, so I picked up the middle ones.

They are much bigger than they look sitting under the car.

The cover the area between the sideskirt to just inside the main frame rails. The body tapers downward toward the back. These plastic parts fill it in making it parallel with the ground.

After drilling way too many holes and laying down some spraypaint to prevent rust, this is what I ended up with.

Here's a factory pic for reference

And some subaru undertray pron for fun.

Haven't checked yet, but I think my exhaust is hanging too low to bridge the center with a flat sheet of aluminum. That'll probably be a summer project anyway.

Overall, I got longer coasting distances out of these panels, and about +1mpg at highway speed.

naturefreak 06-03-2011 11:27 AM

This is a great idea. I actually happen to have a bunch of old street signs out in the garage, and it looks like I will be putting them to good use. This looks like it would be a very simple way to maximize my gas mileage, and I already have everything I need to do it. Thanks for sharing this.
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chris_kraft3 06-11-2011 02:47 AM

I appreciate your photos. They look very good, both cars. I am now more excited to get going with this project myself.

I like seeing guys with faster cars trying to aero mod for a cause.

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