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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!
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