This is a project that I’ve wanted to do since I got the Karbonius air box. The car was in the air for an oil change so I figured it was a good time to do this project. It’s a bit of a distraction from the MK2 but w/e.

Some other folks have integrated the brake ducts in a similar manner for the OEM/flap style airboxes, but none of them were exactly what I was after. I wanted something that keyed into the OEM wheel well sheet metal and fed from the fog light area. The E46 fog lights don’t do a whole lot besides get broken from rocks on the interstate, so I deleted them with some blanking plates a few years back. I also wanted to keep the original brake ducts. I’m not confident they really do much without additional piping to the brake heat shields though. A final goal was to close out the hole left by the stock air cleaner assembly.

The first step was to 3D scan the area behind the headlight. This gave me enough data to create a test part that I could use (along with a more rudimentary duct that I created earlier this year) to locate features in a secondary scan. I could use the secondary scan to design parts. The scans were a little sloppy but that was totally fine for this application.

With known geometry and aligned scan data, I could get to work on a new design. Then, I printed the parts up and epoxied the lower duct together with the fog light bezel. The upper and lower ducts are held together with a plastic expanding rivet and the upper has a really nice compression fit on the frame rail so no fasteners are needed. As the fog light is no longer installed, the lower duct and bezel need a little additional support. A small strip of VHB holds the bezel to the inside of the bumper. This is entirely concealed when installed. The ducts are made from ASA which will be fine from a temperature, strength, and UV resistance standpoint.