Original Submission by T August 30th 2006;
Detonation and Pre-Ignition:
When the ignition occurs at the correct time but burns the mixture burns too rapidly.
Pre-ignition is when combustion is initiated prior to the spark occurring.
The spark occurs earlier than the manufacturer's specification.
Causes of Detonation and Pre-Ignition:
One big factor in detonation and pre-ignition is combustion chamber deposits.
These are most easily formed when an engine has weak ignition, insufficient spark advance
and the engine doesn't see enough load.
Glowing deposits are the usual cause of the trouble and the trouble is
often mitigated by proper use of the engine in addition to having
any weak ignition or inappropriate spark setting cured. Proper use
would be cruise power for a sustained period.Faulty TVS causes pinging
Combustion Chamber Deposits and Pinging:
An excerpt from LMH's PCV page submission.
Submitted by Lovemyholden on Fri, 23/12/2005 - 02:32.
... Or so I thought! Over several thousand K's I noticed my car started to ping under load. Strange, I checked timing, all ok! After a while it got so bad couldn't even do 100KPH without severe pinging. No alternative, take the head off and inspect combustion chambers. I found large sheets of thick carbon flaking off the pistons. I couldn't believe it. Motor is in good shape, good rings, guides etc, why is it burning so much oil.
End of LMH's PCV Page submission.See the PCV page for full details.
Clearing Combustion Chamber Deposits:If the above items are properly set then combustion chamber deposits
will diminish and so will detonation and pre-ignition.
Light loads with weak ignition and poor advance also causes
the piston ring grooves to fill up with carbon. The piston rings
will then no longer gas pressurise.