One of my winter projects on the M3 is brake ducting. I made some progress on that recently.
3D printed brake duct I designed. They are not cleaned up
at all, because I didn't know if they'll be final.
They attach to the factory mount points, and run the air through the center of the factory brake duct/underbody mount bracket, so there won't be any hard bends in the 3" soft line.
They
don't attach to the factory bumper, which means no unsightly screws visible on the bumper and taking the bumper off isn't a PITA:
They do fit with the fog light mount bracket attached.... but it's ugly.
Soooo... painful to do, after 15 years of faithful service from this bumper, but time to trim:
How it looks with the fog light mounting provisions all trimmed off:
Please excuse the Tesla like panel gaps in the bumper. Nothing was clipped in place because it was just a test fit-- still had to install the passenger side.
On the rotor side, I'm planning to use the
Hard Motorsports 355mm BBK rotor duct, as it's the only solution I know of that's designed to work with 355mm rotors. It also vents into the center of the rotor, instead of the face, which is the correct way to do it (I was talking to one of Brembo's engineers, and his take was the ducting onto the rotor face on one side, but not the other, was worse than no ducting at all).
I did make an alternate version of the duct that include an intake air feed for the CSL box, similar in concept to the Evanturi bumper scoop. I'm going to monitor my IATs and install it if they're elevated vs ambient (they weren't before when above ~10mph). If they're not, I'd rather have equal brake ducting for the driver and passenger side.
I'm pretty enthused with the "look" of it, installed. That's pretty rare for me-- I almost always hate any change initially. But, I think they look "stock" if you didn't know the e46 m3 came with fogs from the factory. That's my criteria for any mods that change the look of the car-- if someone can pick out any given part as aftermarket, I don't want it on my car.