1995 Miata, wasted spark using a coil pack with internal ignitors....  I need to view the dwell which you'd typically do by getting a trace of the ignition primary (coil negative between the ignitor and the coil) bt that's no so easy to do with a coil pack with internal ignitors...  any ideas?

Hi Jerry.

Viewing primary voltage on these systems is impossible.  Use your low current clamp and look at primary current.  Then you will see the dwell  [smiley=happy.gif]

Thanks Tom-

It appears I can meet my needs by taking a trace of the signal the stock ECU is sending the ignitor and measuring the rise time, then I can adjust dwell with my standalone to match the same rise time, which is what I was after.  This seems to be working well thus far...

Jerry,

The IC command may not be the same as dwell.  For direct power transistor ignition, it is.  The IC time high (not rise time) is the dwell because the computer controls the dwell.  In other systems, an ignition module controls the dwell and the IC command just serves to control spark timing.

I don't have any captures of this model to say for sure which it is but the diagram below shows an ignition module in the coil.  To answer this question one would need to capture the IC and primary current together.  In any case, the primary current will always be the dwell, whereas the IC signal may not.

---