brunokc:
its for a 1/4 mill track car. so the shift is at the same rpm every time, no down shift.
i have a arduino running the pnumatic shift in a test setup now.
Well, it seems you have the output solved. The only other thing to consider is how long it would take the arduino to effectively shift from when you order it to shift.
I think my link above probably solves the input. Optimal acceleration only occurs at the same point if the gear ratios are the same. initial gear*multiplier^n-1. Where n is the gear. Usually they are not exact. I would see if the OBDII would output the gear and create specific shift points. Otherwise you could use speed and RPM to determine the actual gear.
This seems like a very manageable problem to solve. Let me know what you figure out. I have thought about doing this with my 73 charger.