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Jason and I talked to a lot of vendors that make these kits at the PRI show in December 2016, with an eye on working with this M3. After weighing all of the options (DCE and EPAS), home built vs aftermarket, we went with the EPAS Performance kit shown above.
Ford Racing EPAS unit for 2011-14 Mustangs
There are generally two ways electric assist is used (outside of the early systems which used an electrically powered hydraulic pump with traditional lines and hydraulic assist) on OEM cars these days: the electric assist is built into the steering rack (shown above) or it is built into the column. The latter is what most of the aftermarket is using and frankly its easier to integrate into a car that came with hydraulic assist.
Of course integration with a motorsports steering column would be even easier, but for a number of reasons we wanted to keep the OEM steering column intact on this car - for a working turn signal stalk and some other bits. This BMW steering column was cut apart, modified, and the motor assembly was merged with it.
There are a lot of steps that this "merging of columns" that I'm skipping. Frankly he did it quickly and we didn't get pictures of each step. But it was possible to get the two columns to work together - with some cutting, custom machine work, TIG welding, and careful measuring.
This is the final E46 M3 column with the EPAS system integrated. There are separate controllers and two heat sinks that keep the electronics cool, and a knob that will go on the dash to control the amount of assist, from heavy to light, based on your need. Autocross will likely have a heavier assist, track use less so.
The column was mocked up in the car to get the height and tilt close, then a mounting bracket was built and welded to the cage dash bar to set it in place. The factory tilt is still operational but the telescoping is gone due to the massive changes to the column that were needed. The seat can move fore-aft so that's not an issue.
Below the column a 2-piece steering shaft was built using our BMW-specific U-joints and some DD shafts to connect to the steering rack - we've built and sold hundreds of motorsport steering shafts for BMWs. A column mount bushing and plate to cover the large hole in the firewall will be added later. Now it was time to modify the M3's power steering rack...
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