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Date: Sun, 30 Apr 2006 21:21:53 -0400
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From: Walter Atkinson <walter@advancedpilot.com>
Subject: Re: [LML] pre-ignition


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Paul:

As it turns out all of this concern over some hot particle of carbon=20
causing pre-ignition is misplaced.  That is actually quite rare.  The=20
common causes of pre-ignition are a failed spark plug ceramic or a=20
helicoil tang sticking into the combustion chamber.   We have files of=20=

pre-ignition that is stopped before damage has occurred by pilots who=20
understood what their engine monitor was telling them and took action=20
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=20
that pre-ignition could occur as much as 90 degrees before TDC.=20
In=A0re-reading the article, here is what he says: "I want to emphasis=20=

[sic]=A0that when most people think of pre-ignition, they generally=20
accept the fact that the charge was ignited before the spark plug=20
fires. However, I believe they limit their thinking to 5-10 degrees=20
before the spark plug fires. You have to really accept that the most=20
likely point for pre-ignition to occur is 180 degrees BTDC, some 160=20
degrees before the spark plug would have fired because that's the point=20=

(if there is a glowing ember in the chamber) when it's most likely to=20
be ignited. We are talking some 160-180 degrees of burn being=20
compressed that would normally be relatively cool. A piston will only=20
take a few revolutions of that distress before it fails. As for=20
detonation, it can get hammered on for seconds, minutes, or=A0hours=20
before any damage=A0occurs,=A0pre-ignition damage is almost =
instantaneous."=20
This article is a must for anyone who wants to run a lot of boost!=

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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:


<fontfamily><param>Arial</param>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=A0re-reading the article, here is what he
says: <italic>"I want to emphasis</italic> [sic]<italic>=A0that 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=A0hours before any damage=A0occurs,=A0pre-ignitio=
n
damage is almost instantaneous."</italic> This article is a must for
anyone who wants to run a lot of boost!</fontfamily>=

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