the importance of detonation

"Knock is virtually always the cause of failure in a supercharged engine." "The pressure spike caused by the [detonation] explosion can reach several thousand PSI, and pressure rise is rapid enough to be considered an impact load. These temperatures and pressures are almost ten times higher than those accompanying controlled combustion. . . No metals in existence today, no forged pistons, no special head gaskets can withstand sustained detonation."

Corky Bell, "Supercharged!: The Design, Testing, and Installation of Supercharger Systems," pp. 27, 178.

Further, the load on a rod is a mixture of tensile loads at the top of the compression and exhaust strokes and compressive loads during the power stroke. Yet on the power stroke, the compressive load of combustion helps to mitigate the tensile loads, which are unchecked during the exhaust stroke. Thus, the tensile loads on a con rod are greatest when at TDC on the exhaust stroke, where it is purely a function of piston weight, RPM, and stroke -- not boost.

Bottom line: At 14 PSIG, peak rod pressure is only up about 20%. See Bell, pp. 21-24. With detonation, peak rod pressure is up about 1,000%.

And detonation does not have to be audible to be damaging.  Superchargers mask the sounds of detonation.  Detonation strong enough to cause forces many times greater than normal combustion may not be audible -- even on an NA engine.

The Ford engineers use Kisler probes to watch cylinder pressures in real time. Detonation has a distinct pressure spike. This spike can be 100% greater than normal and still not be heard. Under these inaudible detonation conditions, if a rod is marginal, it will break. You now have a broken rod and no audible detonation.