Its called Multiple Spark capacitor Discharge.

There is a MSD brand of electronic ignition system here in the states
that is very popular.

Paul Lamar

At the risk of injuring some sacred cows I'll put in my  $.02  here.

True, MSD (multiple spark discharge) is the only way to get long

duration

with CD type ignition and MSD (the company) makes a fine one.   This

is as

compared to "regular" CD which gives a very short duration spark.  The

price

you pay is the  weight of this system and high power consumption as

well

as

a pretty hefty price.

It should be pointed out that electronic ignition is not synonymous

with

CD.

Most all cars are equipped with "EI" these days but this just means

that

the

timing and switching of the coils is done with electronics instead of
mechanical points.

 Inductive Coil ignition (as opposed to CD) inherently gives a nice

long

duration spark which is important when doing lean burn combustion

(what

you

should be doing 95% of the time in an airplane).  Magnetos give a

longer

spark than straight CD but usually less than inductive coil ignition.

Another factor in ignition is energy in the spark.  CD (especially msd

type)

is potentially the highest here but there are exceptions.  The Ducati

CD

used on Rotax engines is so weak that its hard to see the spark in

daylight.

I know people who have spent days trouble shooting this ignition

system

(because they couldn't see the spark) when there was nothing wrong

with

it.

The energy in Inductive coil & magneto type systems depends on the
particular coil involved.   Magnetos are usually at a disadvantage

here

because of the small coil size.   The 86 - 92 Mazda coils are

relatively

high energy type (and this is reflected in their weight).

My advice to those using the Mazda rotary for aircraft use is to use

the

stock coils unless you have a very compelling reason not to.   In the

RPM

ranges we are interested in (about 6500 rpm max), there is very little
advantage to using anything else.  Those who claim that there is a

world

of

difference when using something else are either talking about

operation at

the far end of the performance spectrum or they are dreaming.  Gains

due

to

ignition changes are purely due to improvements in efficiency (which

is

wonderful) so don't you think Mazda would have done this is the

improvements

were this dramatic?  They were so desperate for efficiency gains

during

the

design of the second generation RX7 (1986 - 1992) that the project was

going

to be cancelled if they didn't find a way to reduce the car weight by

ONE

GRAM per design  team member.  They sweat bullets and spend millions

to do

that.  Trust me, if a better ignition system would have done the job,

they

would have done that instead.

  True, there IS a big difference if you are going to run at 9000 rpm

(like

the Racing Beat 3 rotor project) but the average airplane builder

would be

wasting their time (& money) going on a quest for the ultimate

ignition

system.  But, (as Dennis Miller says) that's just my opinion, I could

be

wrong  :-)

Tracy Crook
   rws@altavista.net
Web site:   http://www.rotaryaviation.com

Tracy,
How/where do the LS1 coils fit into the discussion above?
Thanks
Dean Head

The short answer:   The LS1 coils deliver about the same energy and duration
as the Mazda coils.  They manage to do this in a lighter weight package by
using a magneticly biased core.

Tracy Crook
tcrook@rotaryaviation.com
www.rotaryaviation.com

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