What is detonation or pinging?

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As mentioned, pre-ignition is a carbon glow plug happening. Not only does carbon absorb some of the fuel down those tiny layers of cracks, but this also helps feed that glow plug if there is a lot of sponge spots that can cause a pre-ignition to occur.

The detonation part is where you add so much air and not enough fuel to cool the kinetic speed that the piston/compression is now under. It is now compromised by say we run up a hill with a lot of throttle and that is a low vacuum pressure as in more air just came in than fuel. And that slight widow of once, lean-cool; is now heating up by the excessive oxygen as it tries to light itself matching almost in the speed of the spark.

So, when the spark is sent, that piston is more or less at or near TDC. I have heard that sound, pulled spark plugs; used a pencil type scope to view the piston dome by accessing the plug hole. I see my center part of the piston where they use that indent to spin the piston on the lathe.

I see that all in tiny balls of boiled aluminum welded together like some DNA line, or more like a bowl of silver marbles where that center indent was. And that was where the spark plug is positioned too, meaning, right over the center of the piston dome. This is what I see on the detonation end of my piston. Once I heard that knocking riding up the slightly steeply graded driveway; that is when I pulled my scope out, took the plug out to see what damage I caused.

So if you want to know where and when detonation hits, I have a little experience monitoring my poor running tuneup. I too am not that expert you keep looking for. Keep looking though. There are many here. I am not one of them. I am still learning the ropes.