Ok... I have been digging around the various pages on the mega/microsquirt site for info on the needed trigger signals on a 4-cylinder, I think this info is equally applicable for a 2-cyl
It appears that for a 4 cylinder with even firing intervals (every 180 degrees of crank rotation) a cam trigger wheel is NOT needed, a crank trigger with missing tooth will suffice. Basing this conclusion on this page (example setup #3) and some bits from other spots on their website
Trigger Wheel Config
The cam wheel + crank wheel configuration is only required with odd firing inervals, like a v-twin or triple, and with applications requiring COP (coil-on plug); which I dont know an example of maybe some auto engines.
SO on a 4-cyl with even firing, a crank trigger with missing tooth can be used alone, with wasted spark configuration and batch fuel injection setup. The microsquirt cannot run 4 individual injectors AFAIK so 2 banks of 2 injectors each is how we setup for a 4-cyl . Along with using 2 coils, and 2 spark plugs tied to each coil.
These details are for what I consider a 'full install' which will include control of fuel and timing maps. A 'fuel only' install can be done by using the signals from the OEM timing system. To me its silly to do fuel only, the hard part will be the TB retrofitting, and plumbing the fuel lines/pump/regulator which has to be done regardless. From what I can tell right now, going from fuel only, to a full install only requires the addition of a trigger wheel/sensor and different coils.
I am doing a lot of reading off of links on this checklist page they have for an install, its equal parts helpful and confusing!
Microsquirt Quick Start Guide
I have sourced throttle bodies from a 2001 gsxr-600, with a fuel rail and injectors. The injectors from this bike are high-impedance (the good kind) and it looks like the throttle position sensor will be easy to wire up to the Microsquirt. The TB spacing with this rack is off but I think I will be trying to use flexible rubber boots to compensate for the offset rather than try to respace the TB rack. This TB setup came with a solid fuel rail which would have to be abandoned and replaced if the TB spacing changes. Im hoping some flexible boots between TB and intake tract will be easier than a new fuel rail. Removed the sub-throttle plates I do not want to have to deal with setting up idle-valve control looks like a potential headache.
Going to look at suitable trigger wheels and sensors next!