Super cool project, I love it!

I've been thinking for a long time that an Arduino Due might make a good base for a fully open source ECU (open source hardware as well as software) but the BeagleBone Black is probably a better choice. Tons of I/O and way-more-than-enough CPU and storage.

The Speeduino being 4-channel fuel and 4-channel spark kinda kills it for me - it's great what they're doing, but it seems like they're just one hardware revision away from proper control of a V8. And I want my fuel injections timed with the valve events at idle. :)

Personally I like the table-driven approach of typical ECU software (especially 2004+ Subaru stuff since it's all 32-bit floating-point) but if you come up with open-source designs for capes that handle interfacing with injectors, coils, sensors, etc, then I bet you'll find other people writing different kinds of software to control it all. Probably including me, eventually.

Are you using Linux on the BBB, or does it boot straight into your ECU software?