Paul:

As it turns out all of this concern over some hot particle of carbon causing pre-ignition is misplaced. That is actually quite rare. The common causes of pre-ignition are a failed spark plug ceramic or a helicoil tang sticking into the combustion chamber. We have files of pre-ignition that is stopped before damage has occurred by pilots who understood what their engine monitor was telling them and took action within a minute or two.

Walter


On Apr 30, 2006, at 12:53 PM, Paul Lipps wrote:

Forgive this old fart's faulty memory; In my previous posting, I said that pre-ignition could occur as much as 90 degrees before TDC. In re-reading the article, here is what he says: "I want to emphasis [sic] that when most people think of pre-ignition, they generally accept the fact that the charge was ignited before the spark plug fires. However, I believe they limit their thinking to 5-10 degrees before the spark plug fires. You have to really accept that the most likely point for pre-ignition to occur is 180 degrees BTDC, some 160 degrees before the spark plug would have fired because that's the point (if there is a glowing ember in the chamber) when it's most likely to be ignited. We are talking some 160-180 degrees of burn being compressed that would normally be relatively cool. A piston will only take a few revolutions of that distress before it fails. As for detonation, it can get hammered on for seconds, minutes, or hours before any damage occurs, pre-ignition damage is almost instantaneous." This article is a must for anyone who wants to run a lot of boost!