340 Pinging using 94
I can take a video.
For the "Vehicles don't ping decelerating", why is that? The engine is still firing while decelerating, it's just doing so at a lower RPM. And if the detonation is now occurring at a lower RPM after retarding the timing, I don't see how it's out of the question.
Now I could very well be wrong, and I am not using experience to justify my thoughts, just logic.
Ping is a description of detonation or preignition. Both can sound like a can of marbles. Detonation and preignition are two separate conditions.
Detonation is a combustion issue caused from a combustion problem. The spark can be occuring too soon, a lean mixture, poor mixture motion allowing a dead spot to get to the auto ignition pressure and temperature.
Preignition is something in the cylinder gets red hot and ignites the air/fuel mix before it is supposed to be ignited. This can be a bit of carbon stuck on the head or piston, too hot spark plugs or a sharp edge.
You stated you do not know about plug temperature ranges. This relates to the heat path for cooling the ceramic of the plug. A hot plug has a long ceramic looking past the ground to where the ceramic is sealed to the metal body. A cold plug has a shorter ceramic. The center electrode and ground will be in the same location for a plug style.
Conventional plugs have the electrode close to the height of the end of the threads of the body. Extended core or tip plugs have a longer ground and the electrode and ceramic stick farther into the combustion chamber. Depending on the cylinder head design, extended core plugs may move the gap closer to the center of the combustion chamber to equalize burn travel distance. On some engines the extended core could interfere with a piston or valve.
Lower compression and low RPM street operation require a hotter spark plug to burn deposits off the ceramic, which can lead to misfiring. Higher compression, higher loads or high RPM generally require a colder plug so they do not overheat and cause preignition. These running conditions cause higher combustion temperatures which will get the colder plugs up to self cleaning temperature.
I hope that explanation helps.
