Well, I really think you are
adopting a position that is consistent with marketing
information, in that respect, rather than data.
Here is why I hold that opinion:
There are LOTS of good things about
well engineered electronic ignitions. Including those suggested on the
PRISM page you imported.
But systems that are designed and
implemented without a complete understanding of the effects sparks, spark
"quality", and real spark timing on the critical combustion pressure
parameters have almost uniformly failed to properly make use of the
potential. I respectfully suggest that includes the LASAR
system.
Is it "better" than just "magnetos"
- - ??? Maybe, maybe not.
If the base magneto is a slick mag,
then there are some issues, right there, to start with. I
have about a thousand hours of experience testing Slick mags on four cylinder
Lycoming engines doing certification runs for the FAA. In one 150
hour test, we experienced failure on about four or
five of them. I am fairly confident that we
have a excellent data based understanding of their spark
characteristics.
If you are comparing their EI spark
"quality" to their slick mag sparks - - well there is a lot of room
for improvement in that case. But do that same comparison against
a pair of Bendix 1200 mags, and the room for improvement in the
spark "quality" gets to be a lot less in many areas of the operating
envelope. There are clearly some areas where it can do
better.
In any event, you are making the
assumption - - apparently without any data - - that the reason you are seeing
lower EGTs is because you are getting a significantly higher proportion
of the combustion events that are more "uniform" as a result of
electronic ignition system operation. You are assuming that a
significant portion of the magneto combustion events do not get a "light off"
of two flame fronts - - and that results in the 70d F increase in EGTs from
two mags firing verses your two LASAR units firing. You
are assuming that the proportion of "poor" magneto combustion events is
sufficient to account for the upward bias of about 70d F in your observed EGT
temperatures.
That assumption is not
consistent with the hard data that occupies a lot of
megabytes on my hard rive. I freely acknowledge that the
issue you raise - - if the mags were truly as bad as you believe they are -
- would be capable of being responsible for some change in the
observed EGT delta - - but not 70-90 F, even using really bad magnetos
as a starting point for the comparison.
The most likely explanation for the
observed results (decrease in EGTs with LASAR) is that the LASAR system
is causing the Theta(pp) to happen closer to TDC than is the magnetos
(even on events in which both the magnetos and the LASAR both do a good job of
firing the sparks) - - and that is what explains the earlier burn times in the
fuel/air charge.
Regards, George
PS. While PRISM will like lower EGTs
under a lot of critical operating conditions (cruise at high power while
LOP, for example), it will likely RAISE EGTS (for good and
proper reasons) under some other critical conditions, such as in
full power at takeoff.
That is why I keep asking you if the LASAR
system raises or lowers the EGTs at full power and full rich mixture as
compared to properly timed and set up set of magnetos. If it
does, it is likely doing the wrong thing for your engine at the wrong
time.
******************************************
Later, you reply thusly:
<<<<<>> 3. Do
you mean that the spark energy, shape, duration and consistency is of the same
quality for electronic ignitions and magnetos? <<
No. In some cases, it is worse
for electronic ignitions !!
But, properly done, electronic
ignitions can improve on the important aspects of the initiating sparks that
start the combustion events. It just requires that the electronic
stuff be originally designed with a really thorough understanding of what
is important about the combustion events. From what I have
observed, this is not always the case.
>>>>>>>>
Again, the "NO" would have been
adequate. Of course, you have to qualify it with "some cases", fixed
later with "Properly done" and deflated later with "this is not always the
case. Frankly, I am only presently concerned with my case and the data
which I am capable of collecting. I am trying to learn but there is no
learning when you try to tell me only how things fail to work.
******************** I really did
mean what I said. Some EI system spark events are worse (for
the engine) than some magneto spark events.
*****************
>> Well, we shall see from
the tests that I am going to run. BTW, what kind of EGT drops are seen
with PRISM? I know they occur because PRISM claims a "significant"
drop. Unison predicts 70-90 degrees on the LASAR (if I remember
correctly). Maybe this is what Cy meant by "relative." <<
If you
don't collect the right data, then the tests will not shed any new light
on the subject.
At a
minimum, what needs to be collected to be definitive is the
following:
1)
TDC measured continuously to better than 0.5degree
resolution;
2)
Internal cylinder pressures sampled at least at the same 0.5degree resolution
3)
High speed measurement of the ACTUAL spark event for each plug, including a
measurement of the energy of the sparks;
4)
Computation of the coefficients of variability of peak
pressure, Theta(pp), IMEP;
5)
EGTs and CHTs;
6)
Fuel flow and MP.
What UNISON
"predicts" - - - or has even measured is not the issue. The
reason is because there are two independant issues - -
and you are failing to deal with the dominent issue of WHEN the spark
(actually, not as measured by static timing settings) goes off - - rather than
the "quality" of the spark issue. I submit to you that WHEN the
spark goes off is an issue that dramatically overshadows any differences in
consistency and/or "quality" of the sparks from EI systems verses Magneto
systems.
That is not
to say that improvement in the quality and consistency of the spark is
not a "good thing". It is. It is highly worth while. But not
for the reasons you are suggesting.
Regards, George