Timing monitoring for magnetos?

[kaa]

Hi all,

This is mostly idle musings, but I was wondering why there is no solution for monitoring magneto timing? I used to own a -7 with P-Mags and I really liked the info that the EI Commander provided, especially around timing divergence.

Given that magnetos have potential nasty failure modes where timing becomes advanced or erratic, why is there no solution to monitor this? It is already possible to read out RPM from p-leads, it seems like it should be relatively easy to monitor pulse trains from both p-leads and at least alert if one of them becomes erratic or if the timing diverges.

 

[rmarshall234]

I've never heard of a magneto failure that advanced timing and caused detonation. Not saying it hasn't happened, I've just never heard of it. I would consider them "fail safe" in that regard. Electronic ignition on the other hand...I've heard of several failures which have caused advanced timing and detonation and the resulting engine damage. I've been saying for 10 or 15 years now, that I would never consider an electronic ignition system which did not provide for a cockpit display of the timing advance.

 

[kaa]

Mike Busch lists a few failures in his articles and this webinar (which is what got me thinking about this). I guess failures with purely advanced timing are unlikely, but erratic timing is not that uncommon it seems?

 

[rocketbob]

it seems like it should be relatively easy to monitor pulse trains from both p-leads and at least alert if one of them becomes erratic or if the timing diverges.

One would have to have a crank trigger to compare the output of the P-Lead and if using that mechanism to as a diagnosis, there are conditions that would not be diagnosable via the p-lead, such as a shorted secondary.

Cars have various knock detection mechanisms. Air cooled engines are too sloppy mechanically to employ something similar.

 

[hgerhardt]

..............Cars have various knock detection mechanisms. Air cooled engines are too sloppy mechanically to employ something similar.

Actually, Lycoming's TEO-540-C1A has a knock sensor on each cylinder, circled in red below.
Surprised the tech of that engine never made it into any other models.

 

[rmarshall234]

I think our engines are too "noisy". But I'd be happy to be corrected on that.

 

[Desert Rat]

That's basically what you're checking when you confirm that the rpm split between the two mags is within tolerance on the runup.