In article
,
says...


We older guys can remember a time when cars would "ping" or
"knock" when the engine was driven at a low RPM and too much throttle.
That was detonation and it would break rings and knock holes in
pistons and trash the bearings and sometimes heads and cylinder walls
would crack.



Careening wildly off course here, but in truth the evidence is not that
clear-cut about the damage done to automobile engines from "knocking".
Recalling my UofM courses on the subject, the text even reproduced a study
of tear-down examination of engines after many hours of heavy knocking in
a laboratory controlled environment, and the results were inconclusive as
concerns damage to engine components.

The main concern with knocking, in car engines, is that once IMEP exceeds
KLIMEP the power starts to fall off rapidly; therefore this represents an
absolute performance limitation for any engine.

I am willing to accept that things are different in the world of aircraft
engines, where slow rotational speeds and turbocharging may lead to
extreme detonation conditions, if mismanaged.


Sources:
http://www.me.umn.edu/education/courses/me5461/

Internal Combustion Engines, by Richard Stone, 3rd Edition, SAE 1999