Had some time to scope the ignitor. Dwell, defined as the period that the coil is shorted to ground, does in fact adjust for increased rpm. At idle, dwell starts around 20-25 degrees before the ignition event occurs. This is longer than the IGT signal! As rpm increases the dwell angle is increased to allow for more time to charge the coil. The ignition coil is actually charging before the igt signals positive slope! Meaning before the ignitor even knows of a timing event from IGT, its preparing the coil. I had a few work arounds to remove the ignitor on the stock ecu but a bit more thought is needed..
Either the IG-A/B signals are triggering the start of the dwell angle, or the ignitior is much smarter than i had hoped. If it is IG-A/B, it will be interesting to see the signaling going on. more to come.
My stock setup really liked 3.12 ms of charge time. After the coil charges for 3.12ms, it is pwm at 800hz to avoid an over charge for the rest of the dwell period. Not sure if this is actual current sensing going on, or a constant value of 3.12ms. Please note that the actual dwell time is longer.
Attached is a graph from a guy over seas. He put many coils through their paces for the megasquirt crowd. Luckily the 7m coil was one. Can not validate the setup he used to test though. His graphs from other coils match those posted by other testers in different parts of the globe. Leading me to think his methods are close enough. Mainly the 1zz coils. Stock coil seems to be capable of packing a PUNCH, just not enough charge to do it..
If the ignitor is sensing current, seems 7.5a is likely charge level.
Edit: accuracy corrections.
