In a message dated 3/27/2004 10:40:15 PM Central Standard Time,
walter@advancedpilot.com writes:
That is
an indicator that the REAL timing is NOT right. Lower EGTS are the
result of advanced timing. This is NOT good. If the timing is
correct the EGTs will NOT be lower. PERIOD. This is one example of
when lower temps are NOT good.
We have tested magnetos and electronic
devices and find that the actual spark event does not coincide. This can
be VERY bad.
Walter,
Pleeeeeeease. I know that the sky is falling and my engine is headed
for doomsday 'cause I haven't been to an advanced pilot seminar - but, at least
try to help us understand why our observations, experience and understanding of
ignition events at altitude are not just the product of hypoxia induced
lightheadedness.
1. You mean the PRISM system doesn't use modern electronic
ignition components and controls, including timing?
2. Do you mean that fixed timing, developed via compromise, is the best for
all operating conditions?
3. Do you mean that the spark energy, shape, duration and consistency is of
the same quality for electronic ignitions and magnetos?
4. Are you telling me that our excess fuel delivery systems are so good
that no combustion is occurring in the exhaust pipe near the EGT probe?
5. Do you mean that magnetos deliver a consistent spark (time, duration and
strength) 100% of the time when one manufacturer states that there can
be magneto spark impairments of up to 10% of the time? And, that
this deficient combustion in the cylinder might lead to some combustion
completion in the pipe?
Considering my experience, that ".. magnetos and electronic devices
and find that the actual spark event does not coincide" is a good
thing.
Scott Krueger
PS: BTW, For my Lyc I/O 320, electronic spark advance does not occur above
26" MAP (generally below 4500-5000 Palt), and then gingerly so thereafter with
little power effect, even with the reduced fuel flows. For my case this
is yet awaiting further study. Still, above 26" I see reduced
EGTs.
PPS: How accurate should the timing be? + or - 2 degrees? + or - ?
degrees?