Great 109 article

[Vraciu]

Then why did they develop this system if all they needed to do was lean out the mixture?

You'll have to ask them.  And they're the only ones who did it that way apparently.   Perhaps they felt it was worth the effort.

In any case, I doubt such a system would have helped the P-38, which had issues with it at altitude.    Fouling is caused by low temps in the combustion chamber which allows lead to accumulate on the plug.   At some point, if you don't fix the problem, the plug will foul completely and nothing will cure it short of removal and cleaning.  If leaning the mixture or using a high power setting doesn't burn the lead off it's probably too far gone to cure.    You can't retard the timing on a cylinder with plugs that can't fire.   

[Vraciu]

Someone should page Columbo on this.  I'm sure he has something relevant to add.

[Denniss]

Ignition timing was automatic, based on power setting. With fuel injection it was probably easier to change ignition timing than to change the amount of fuel injected. According to DB 605 manual there was a lever which changed ignition timing to late (Spätzundung) to clean spark plugs, releasing the lever reverted timing back to auto.

[Krusty]

What worked with US engines did not work with German engines. The fuel type was based on synthetic coal derivations. Even the octanes did not properly compare to each other. Flying a captured german plane like you would a US plane would lead to fouled plugs in very short order. The design and utilization of the engines in these warplanes were exceedingly different from each other. Even down to the basic voltages used on everything.

[icepac]

I always go lean to "defoul" a spark plug from c150s to 3350s to our 2700hp ford Gt.

[save]

You could shut down one of the 2 coolers if one where hit. I wish AH that this feature.