Ignition current ramping

This is from an Ignition coil cassette assembly at startup the current is 17 amps and then goes down to 9 amps I am on the ground to the cassette. How is this possible I think it must be the alternator charging too much any thought on this?
This is from an Opel Astra 2005 XEP16 engine I still working on this car but that's another thread I posted a new one because it is a general question about current on ignition coils

Next slide low current after startup

Might be doing something to deliberately generate a stronger spark at startup. I doubt an '05 has an actual ballast resistor but may be performing the same function electronically.

Going after the alternator based on those waveforms is a rabbit hole IMO.

I'd be interested in comparing the on-time of the coil when it's at 17 amps, compared to when it's less than 10. Is the on-time for the coil that much longer right after startup? Or is the on-time the same.

I also think the alternator is a rabbit hole. BUT, if you really wanted to prove it, you could disconnect the alternator and prevent it from fielding during startup.

Tyler wrote: I'd be interested in comparing the on-time of the coil when it's at 17 amps, compared to when it's less than 10. Is the on-time for the coil that much longer right after startup? Or is the on-time the same.

I also think the alternator is a rabbit hole. BUT, if you really wanted to prove it, you could disconnect the alternator and prevent it from fielding during startup.

On-time is the same

Next Saturday I try to get the car all day and test it again to see if it is a one-time event.
I am only a diy try to learn and help other people because there is only part changer around and it gets really expensive

spit64 wrote: On-time is the same

Interesting.

I like Matt's theory about the ICM regulating coil current? But normally, when I see coil current limiting strategies, the top of the ramp plateaus out. You can't 'see' if that's what the ICM is doing, because all the magic happens in the cassette.

Can't say I've measured coil current during startup. So I honestly don't know if this is a common strategy or not. Maybe I'll check a few known good cars.

Tyler wrote: I like Matt's theory about the ICM regulating coil current?

I don't :silly:

Just noticed the start up current is about double running. Might be firing two coils at once until it gets a CMP sync?