Originally Posted by bruce.augenstein@comcast.
Absolutely agree on knock doing damage, but I'm actually asking how lugging does damage. My opinion is that a normal M3 is mildly lugging at 1500 rpm, but don't see how that can cause damage.
It will react differently in different gears. It certainly won't be lugging in 1, 2, or 3.
By the way, detonation (not pre-detonation) and pre-ignition are two completely different damage mechanisms. What is being experienced at low load is likely detonation, or the spontaneous combustion of the mixture ahead of the flame front.
Pre-ignition is the combustion of the mixture before the spark plug fires by a hot object in the cylinder. It is far more damaging than detonation.