knocking is natural phenomenon which occurs in ic engine. no scientist in the world is capable to clearly explain this phenomenon but the explain much part of them....
how it occurs... in petrol eng...
"knocking" or "pinking" is the phenomenon in which pressure wave of high altitude generated strikes wall of combustion chamber.pre. waves are generated because fuel attain self ignition temp. before flame front created by spark plug reaches to it.
THE MAIN FACTOR RESPONSIBLE IS PRE-IGNITION.