Comment: Re:10% Ethanol (Score 1) 556
What do you thing pinging/knocking is? It is detonation of the fuel in a non-optimum premature way. I said simple version in my answer, not 100% factually correct version.
Pinging/knocking occurs *after* the spark plug has fired and is the premature ignition of parts of the mix before the flame front reaches them. If the mix self-ignites before the spark plug fires, that's pre-ignition. Two different phenomena with two different forms of characteristic damage (the latter is usually way more damaging). Backfiring has nothing to do with either.
You may think you gave the simple version, but in fact you gave the wrong version.
Also, octane ratings are not obtained by the pressure at which the fuel spontaneously combusts, or at least that is a misleading explanation (makes it sound like you put it in a pressure chamber and up the pressure until it pops). The two primary measures, RON and MON, are both obtained using a combustion engine with a variable compression ratio. It's a much more real-world measure than you make out.