So I was all ready to make my Arduino Mega the CDI of my Yamaha FZ150 Carbed (only made in Taiwan, I think) when I had a bit of a revelation.
I did a bunch of research and learned that as a proof of concept Arduino+MOSFET+12V+ignition coil+sparkplug=spark.
I also learned that a lot of people had success using an Arduino as the CDI to their scooter or 4 cylinder engine(see speeduino).
So I thought 'Why the heck not? The Arduino will take RPM, crank angle, maybe I'll install TPS and MAF or MAP for load as inputs then it'll calculate ignition timing either through a formula or ignition table that I'll figure out for my specific bike.'
Then the revelation hit me. 'Isn't that what the factory CDI is already doing?'
So aside from being able to say I could (which is why most us make microchips control everday objects) and the awesome knowledge I would gain from this project whether I succeed or fail... what benefits would I get from a DIY CDI over the factory one?
I'm hoping someone can convince me to keep trudging forward.
You could even cheat. Use the existing sensors first to "learn" the relevant timings. So have your arduino looking over the shoulder of your factory built CDI.
Then bit by bit, allow it to start taking over the different functions. Maybe at first just displaying RPM then take over the injectors and then finally add in the task of ignition. As you say, the learning exercise is probably the greatest thing you'll get from it, but you could also experiment by adjusting some of the mappings to see what kind of effects they have on performance.
All engine performance is about compromise. You may find that by tweaking the standard values you'll be able to get a performance change that suits you. Maybe more acceleration. I doubt you'll be looking for more fuel economy but this is another possibility. If you find a different mapping table that works better in certain circumstances, you could have it switchable (sports/cruising mode).
Edit: Oops, just noticed you said, Carbed. So no injectors then.
Vashdash:
what benefits would I get from a DIY CDI over the factory one?
This would not be an easy project. I think you will get NO benefits UNLESS you already know of deficiencies in the factory fitted device AND know enough about ignition management to figure out how to achieve the changes you want?.
For example is it possible to buy replacement "improved" chips for your engine? If so how in what way do they change the engine output (I'm assuming the developers keep the software changes secret).
Another reason to avoid the project (IMHO) is that you would need some very sophisticated and expensive test equipment to be able to check whether things are better or worse.