Swapping an N57 into a 335i manual coupe.

[Ragnorak]

Personally, I'd look overseas and build this based around the manual 330d sold to European markets that use the same engine with higher power output. Your electronics solutions may be available off the shelf using that software and then using a JBD type controller to adjust for your desired power level.

[floydr]

Why wouldn't you just swap the transmission?

Why are you replying to a year old post? The OP has given up, or succeeded. The transmission swap was discussed earlier in the thread; did you not read everything?

[TerraPhantm]

Wiring wouldn't be a problem if you follow a 330d as your reference (and BMW is pretty good about keeping the transmission harness pretty much separated from everything else).

What is unknown is software. Some newer BMW ECUs are smart enough to figure out whether or not they're connected to an automatic transmission - and reset to "manual mode" if the adaptions are cleared without a transmission computer present. I do not know if the 335d acts like this since it never came with a manual.

Worst case, you could probably run the 330d software and have it "remapped" for the 335d hardware. Definitely extra work, but not impossible