Paul,

For rotary, any opinion on which is better capacitive ignition or
inductive ignition electronics?

John Fair

The consensus in the rotary racing industry is MSD.
Capacitor discharge Multi Spark, One of my next projects
is to design and build a simple system to trigger off the shelf
dual or quad MSD ignition units. My hangar neighbor has done tons of
R&D on lean burn engines and he claims the more powerful
the ignition the leaner you can run the engine and the lower the fuel burn
up to a point.

http://www.rotaryeng.net/Spark-plugs/Spark-plugs.html


Paul Lamar

Paul-  Evaluation of capacitive discharge will be interesting. When we built
our early electronic ignition system we looked at both inductive and
capacitive discharge advantages/disadvantages.  Everett had almost 40 years
experience testing all the different ignition systems for race cars and
aircraft so we put that to use. The conventional inductive had much longer
burn time but did bleed off, whereas the CD had the fast rise time and no
bleed off (benefits) but a short burn time (disadvantage). We evaluated a CD
system on only the trailing plugs because velocity by those is much lower
(leading plugs 90 meters p/second approx,  and trailing 25 mps) and thought
maybe the CD on trailing plugs would help to prevent fowling.  We  didn't
find a significant advantage or need and opted for the longer burn and
simplicity of all inductive system and switching done back then with the
Mallory infrared triggers to eliminate the need for an amplifier box. The
inductive ignition seemed to be key on the key leading plugs because of high
velocity by plugs benefitted from longer burn time.

Steve Beckham

The new CD ignitions fires over and over again
so the longer burn time is less of an issue.

If you use one MSD per rotor it has more time to fire more than once
at high RPM's.

Paul Lamar