I'm sorry. I can't get my hands on the tch specs, but I will be able to dissassemble it the next few days. It's from a motorcycle, so i'm pretty sure it's a pickup coil.
Just so I don't dwell too much into this idea of controling the sparks with the arduino, could you answer me this: Can the arduino read 14'000rpm (the sensor should send 234 signals per second)? And obviously, send output that fast?