Basically Knock Retard causes predetonation in the cylinders, causing one or more of your pistons to top out and smack the piss out of the head. Which leads to it chipping, or in my case, shattering the skirt
KR does not cause detonation. It is the engine's response to detonation to protect itself.
2004 Impala LS - got some mods sold!!!
2009 Subaru Impreza WRX STI
NAIOA moderator Still Imp'n, just in a different Imp.