The project: A B&S V-twin engine (627 to 810cc). Right now I'm planning only to do EFI and to stick with the OEM "Magnetron" ignition (fixed timing), but I'd like to have the option to perhaps fit a more advanced ignition later. In this application, reliability is more important than fuel economy. Manual mixture adjustment in real time (based on EGT, a wideband O2 sensor, etc) would be acceptable. To keep things simple, I'd think batch injection will be just fine.
1) Would the NO2C board be the right choice? Space is not a giant issue, so if there are advantages to going with a larger Speeduino board (better cooling, easier assembly, more flexibility, etc) I could accommodate a larger board. But, if there's no downside, then the the smaller NO2c board would seem best.
2) MAP sensing: The induction cycle for these V-twins is obviously very uneven, so having an injector for each cylinder will be great. In the carbureted versions, the induction and exhaust runs are kept entirely separate for each cylinder to help avoid having uneven induction pressures/fuel amounts into the cylinders. In a Speeduino installation, would each cylinder get its own MAP sensor? Some people doing tuning on these engines have trouble getting good MAP readings on individual cylinder MAPs, I'm guessing this could be because of the long lag time between induction cycles (i.e. long periods with zero flow, then a relatively short flow period). Will I need to use a special MAP sensor or employ some sort of data smoothing/averaging to get good readings for use in computing fuel requirements?
3) RPM sensing: To keep things simple, is it likely I can just use the OEM magnetron trigger magnet on the flywheel to trigger whatever sensor I'll use for RPM (Hall effect, probably)? This won't give information on what the valves are doing, but just engine speed. Good enough for batch injection?
4) Throttle bodies: Any known good (inexpensive) dual-throat candidates in the 28-30mm range? Some of the motorcycle throttle bodies for 250cc-400cc 4 stroke engines look like good candidates.
5) Fuel pressure: The fuel flow requirements of these engines are pretty modest (2.5 GPH / 10 LPH max). Is it likely I'll be able to use a fairly low fuel pressure (7-15 psi / 0.5-1 bar) in my fuel delivery line? The alternators in these engines aren't big, and I'd prefer to use a pump that draws less current.
6) Speeduino power filtering/EMI characteristics: I haven't done much analysis on how "clean" the power is from this engine/electrical system (particularly during starting), and I don't know much yet about the shielding of the ignition system components. My guess is that clean power and low EMI might not have been high priority issues in the design of these industrial engines. Is the Speeduino hardware already tolerant of voltage excursions, etc, or should I consider taking extra steps?
7) Any known similar projects I should be reading about, or folks who frequent these boards and who spend their time fitting EFI/electronic ignition to these small industrial engines?
Thanks much for your assistance.