I took this capture from the M117 Mercedes V8. After the plug gap increase to .040 my burn time increased substantially as well. Firing sequence 1 5 4 8 6 3 7 2.   Cylinders 1 and 5 looks like they lean out or ?, definitely different than others. Anybody wants to comment on it?

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Good morning,

Is there an issue you're trying to fix?



The first thing I noticed in the capture is that there are no notes and the channel labels are not filled in.

I made the assumption that channel B is on #1 spark plug wire.

Cylinders 1,5,8, and 3 all seem to require substantially more voltage to jump the gaps.

All cylinder firing lines are around 2kV which seems fine to me.

The burn times of the firing lines are all approximately the same which is good.

Here are some changes to the setup that I would do.

Bump up sample rate to 2MS/s
Increase Time base to 200ms/div or more.
Do a snap throttle about halfway across the screen.



Some threads you might find useful.

This tread talks about the kV required to just the rotor gap vs the kV to jump the plug gap.
https://www.autonerdz.com/cgi/yabb2/YaBB.pl?num=1404120057/79#79

This one has some excellent info from Mick on secondary analysis.
https://www.autonerdz.com/cgi/yabb2/YaBB.pl?num=1389665548/24#24

Thank you for the reply.
There is no issues at the moment. I’m just trying to understand that scenario better. Yes I triggered on #1 and pick up the parade from the king lead.
I was under the impression that there was a lot of energy left after the spark because of the high spike and amount of ringing after the spark.