Here are a few charts from Heinz Heislers book Advanced Engine
  Tech and others. The first chart shows that; as the fuel air ratio
gets real lean and the pressure lowers in the combustion chamber at
high altitude the voltage required to fire the plugs goes up. Klaus
has exploited this situation to lean his engine out at high altitude
and improve the BSFC to remarkable levels by increasing the spark
voltage. He has achieved as much as 100 MPG at 130 MPH and 60 MPG at
more reasonable cruising speeds. This is a piston engine where the
spark plugs are at one end of the fire and the piston is at the
other end.

     In our case we have a moving combustion chamber where the fire
  travels along side the spark plugs for quite some time. IMHO We
want the spark plugs to continue to fire for as long as the unburned
and burning mixture is still present moving past the plugs. That
takes 8.3 ms at six thousand RPM cruise RPM. See chart 2.

  A capacitor discharge ignition system  is very good at firing
  spark plugs fouled with 100 LL but it only fires for .2 ms. Even
  an inductive system (Chevy LS1 coil) or stock Mazda ignition
  only fires for about .8 ms.

     IMHO NO WHERE LONG ENOUGH FOR WHAT WE NEED!

  IMHO we need an ignition system to fire for 8.3 ms or 300 degrees.

  TEN times as long. MSD makes a multiple spark capacitor
  discharge ignition system widely used by Mazda rotary
  engine racers but it only works up to 3000 RPM. After that it
  is "one strong spark" says MSD. Not enough in IMHO. This is why
  I am doing a m.s.d. ignition system with several pre-charged
  capacitors fired in rapid sequence by a cheap single chip
computer. I hope this is a break through in improving the BSFC of
  the rotary engine. I think it is worth a try.

  Patent applied for :)

  --------------------------------------------------

  This is the range of rotor positions I intend repeatedly firing
the spark plug. Mostly the leading plug (lower plug) as one does not
want to risk igniting the mixture in the following chamber.

  Paul Lamar

Good going Paul.  We need the long duration.  Will be very
interesting. Sure wish we access to the Mazda factory development
notes and a supply of the three sparkplug rotor housings the Mazda
factory built for the R26B LeMan's engines to improve efficiency.

Steve Beckham

Paul & Group -

How does aircraft magneto ignition compare with this ? Magneto Sparks
do get longer with higher RPM as I understand it.
Fly & build good -

Bryan in England.