The frequency output expected from that spark plug is?
How much overlap is there?
The engine RPM is going to be exactly the same as the spark plug fire rate. Well, divided by 2 for a four stroke engine. Have you considered just using the engine RPM? I suspect that would be a less electronics intensive project.
So spark plug would go off at a consistent timing if the engine is holding RPM. and we'll have this play at something like 30hz with a variation of 5hz to give it a little life/not be monotone and at 25db.
Then when accelerating as the RPM increases they just multiply the hz and db. so it'd go up to around 400hz (maybe the variation ratio changes, maybe keep it at 5... that'd be something to play with to get the right sound) and 80db
So basically I want to use a board to do an equation along with audio passthrough.
so switch ON:
RPM x .1 = hz
hz with some controlled randomized = hz out
RPM x .05 = db out
(And I have no idea how to turn that ^^^ into an audio signal... This is very much new territory for me.)
just audio passthrough from the speaker wire to the amp...