Hi Mike,

I think I need to clarify some differences here. C&H makes three basic
types of ignitions for gas engines. One is the basic HD unit which is
intended for mechanical advance setups, the second is the HD unit with
Syncro Spark electronic timing board installed in the case with the
standard ignition, the third is the Syncro Fire completely microprocessor
controlled ignition system.

My references in an earlier post apply only to the third, or Syncro Fire
system. In my testing of Bill's standard systems, I found no significant
advantage to using a 6.0V pack over the 4.8V pack. The energy output
increase does not justify the current draw from the 6.0V pack. It will suck
a pack dry rather quickly. I recommend only a 4.8V, 1200mAh (minimum) pack
for Bill's standard HD systems.

The Syncro Fire system, however, does gain some efficiency from the use of
the higher voltage packs. As I mentioned, the processor detects the input
voltage as well as the charge on the output capacitor and adjusts the
output accordingly to maintain the maximum designed output. It is simply a
slightly more efficient circuit at the higher voltages. Syncro Fire is the
only ignition system I am aware of that provides a complete output section
for each plug on twin units. The other systems share the energy in a single
capacitor with both coils and therefore cut the energy to a twin cylinder
engine in half as compared to a single cylinder system. Plug gaps and
conditions become critical then because the spark will follow the path of
least resistance and one plug may get the lions share of the energy and the
other will have a weaker spark.

The advance on both electronic advance ignitions (SS and SF) are linear
(virtually stepless) from full retard to full advance when the throttle is
advanced normally. When the throttle is advanced rapidly, the system
detects this and advances faster. I know we have discussed this in the past
and I intend to follow up on your suggestion as time permits, but for now,
we are staying with what we know works on the engines we fly.

Regards the higher RF output, the potential for RF noise increases with an
increase in output energy. However, a properly designed system with
shielded spark plug leads and other precautions reduce this effect as a
potential problem. Bill's standard HD systems are properly designed systems
as well as the Syncro Fire system. Some other ignition manufacturers get by
without shielding and such precautions because the output is very wimpy as
compared to the C&H systems. They fire fine as long as the plug is new and
clean, but will start to misfire at higher RPMs when things are not so
perfect. Folks then start adjusting on the carb and griping about how bad
the engine runs when all it needs is a new plug.

Sorry to be so long winded.<G>

Regards,

Ed Vollmer
ME Technical, LLP