Re: [ST] st Digest, Vol 15, Issue 1

[Jonathan West <triumphnutter@xxxxxxxxx>]

Hi Rod,
You're exactly right.  Pre-Ignition is simply the air fuel mixture igniting
from another source other than the spark plug.  Typically it's carbon buildup,
and sometimes just a hot spot in a poorly designed combustion chamber or intake
tract that can fire off the mixture before it's time.  It can also be referred
to as "dieseling" which is when the engine keeps running after you shut the key
off.  It can lead to detonation and detonation can lead to pre ignition, but
they are not the same thing.

A +4 degree advance sounds like too much to go across the board.  Might be fine
for the midrange and top end, but as mine is now, it would not survive any more
advance on the bottom.  

Are you referring to these "tunes off the web" as maps from Wayne McDonald's
Tuneboy? or Power Commander maps?  


Cheers,
Jonathan West 

Date: Thu, 1 Jun 2006 07:31:12 -0400
From: "Sprint ST" <sprint_st@xxxxxxxxxxx>
Subject: Re: [ST] General thoughts on ping

Johathan,
A couple of points. Pre-Ignition and detonation are two totally separate
issues. Although you did not mention that specifically, many believe they
are the same because detonation is enhanced by advanced timing.  Secondly,
detonation probably occurs when more than one factor is involved.  Lot's of
guys run tunes that they get off the web. Two very popular sports touring
tunes run a +4 degree advance across the board. That definitely will
increase the probability of detonation.  Use 89 octane, AND dial in too much
throttle at a lower gear with that tune, it's a formula for detonation.
Rod 



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