I'd be surprised if its not a 32-bit processor on a 2003, it'll have way more processing power than an UNO, it may not be an issue for you though.
I can't say for certain personally either way. I'm just going by what was mentioned in the doc from the gent that made the "fuelino" project. (/edit re-reading the topic, I can see it's hard to see the PDF I attched up above. It references two controllers on the board. One is customer, this is the other:
https://www.monocilindro.com/wp-content ... asheet.pdf
I always advise against using internal ignitors, you are bringing high voltages and big current spikes into the ECU that can lead to big noise problems. External ignitors and cheap and plentiful if you can't find a smart coil to fit.
Agree, I'm not thrilled from an electronics standpoint and in a way it's impressive it worked in the OEM ECU. CDI's are cheap (Like $7 cheap), but that implementation wouldn't be a standalone ECU IMO.
Do you have enough alternator power to run an EFI? if the original unit used high voltage windings in the alternator then you will be adding a fair bit of additional power draw. On a previous project I had the alternator rewound and replaced the high voltage windings with 'standard' windings to up the power output.
In the standalone use cases, yes they have enough generator power of course. One project I'm working on is actually a lossless system for competition with short run times. For EFI conversions I'd like to implement PWM fuel pressure control
viewtopic.php?t=6325 as an alternative having to find a lager stator.