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From: Walter Atkinson <walter@advancedpilot.com>
Subject: Re: [LML] Re: Where has all the power gone?
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Brent:

Correct.  I would to your list of factors affecting detonation, the=20
lantecy period of the fuel.  That's a biggie.

Walter


On Dec 29, 2005, at 9:01 PM, Brent Regan wrote:

Ron asks:

  "Retarding the spark timing helps to prevent detonation. If turning=20
off one mag has the same effect as retarding the timing (as you stated=20=

above), wouldn't running on one mag help to prevent detonation rather=20
than contribute to it?"

  People tend to think of the ignition / combustion event as=20
instantaneous but it is not. It is a process that takes time and=20
involves a flame front that propagates across the combustion chamber.=A0=20=

If we define the combustion process starting at the crank angle when an=20=

arc is established across the electrodes of the plug and finishing at=20
the crank angle when 95% of the fuel is burned then we can calculate=20
the crank angle that is half way between these points, call it the=20
median. If the combustion process takes longer then the median occurs=20
later, retarding the overall combustion process even though the static=20=

ignition timing has not changed.

  Generally, detonation seems to be a function of heat, radiation and=20
TIME. Firing two plugs reduces the time and starting the process later=20=

reduces the heat and radiation.

  During runup, turning off one ignition source has the same effect on=20=

RPM as retarding the timing in this case but the static timing remains=20=

the same.

  Regards
  Brent Regan


 =20=

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Brent: =20


Correct.  I would to your list of factors affecting detonation, the
lantecy period of the fuel.  That's a biggie.


Walter



On Dec 29, 2005, at 9:01 PM, Brent Regan wrote:


<fontfamily><param>Arial</param>Ron asks:</fontfamily>


<fontfamily><param>Arial</param> "Retarding the spark timing helps to
prevent detonation. If turning off one mag has the same effect as
retarding the timing (as you stated above), wouldn't running on one
mag help to prevent detonation rather than contribute to =
it?"</fontfamily>


<fontfamily><param>Arial</param> People tend to think of the ignition
/ combustion event as instantaneous but it is not. It is a process
that takes time and involves a flame front that propagates across the
combustion chamber.=A0 If we define the combustion process starting at
the crank angle when an arc is established across the electrodes of
the plug and finishing at the crank angle when 95% of the fuel is
burned then we can calculate the crank angle that is half way between
these points, call it the median. If the combustion process takes
longer then the median occurs later, retarding the overall combustion
process even though the static ignition timing has not =
changed.</fontfamily>


<fontfamily><param>Arial</param> Generally, detonation seems to be a
function of heat, radiation and TIME. Firing two plugs reduces the
time and starting the process later reduces the heat and radiation. =
</fontfamily>


<fontfamily><param>Arial</param> During runup, turning off one
ignition source has the same <bold>effect</bold> on RPM as retarding
the timing in this case but the static timing remains the same. =
</fontfamily>


<fontfamily><param>Arial</param> Regards</fontfamily>

<fontfamily><param>Arial</param> Brent Regan</fontfamily>



=20=

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