I just put two and two together. duh!

It occurred to me that the short pulse width of the
regular CD single spark system is of no consequence what-so-ever 
in the rotary aircraft engine as we always run
faster than 4000 RPM. Any pulse longer than 5 ms
is of no use to us  as the combustion process is well over
by that time if my arithmetic is correct.
In other words the expansion cycle is well over by 180
degrees rotation of the e-shaft. Compare these
times with the chart below.

No multiple sparks required.
Yet all the advantages of the CD system to maintain
high plug voltage at high RPM and punch through
spark plug fouling remain.

The optimum ignition timing advance will change because of the
faster rise time of the CD spark. If you don't
change the advance you will not see the advantages.

Most of the ignition work mentioned in the Mazda published
book called "Rotary Engine" by K. Yamamoto focused on the part 
throttle, less 2000 RPM speed range of the automobile application.
That is another reason why they did not use a CD system.
They could have used a multiple spark CD system to advantage
but the cost would probably be prohibitive for automotive use.

Check my math in the basic program below.

 RPM   ...........REV / ..........180 deg.
  ............... SECOND .......... msec.

 500 ........... 8.3 ...........60.00
 750   .........12.5........... 40.00
 1000  .........16.7 ...........30.00
 1250  .........20.8 ...........24.00
 1500 ..........25.0 ...........20.00
 1750 ..........29.2........... 17.14
 2000 ..........33.3........... 15.00
 2250 ..........37.5 ...........13.33
 2500 ..........41.7 ...........12.00
 2750 ..........45.8 ...........10.91
 3000 ..........50.0 ...........10.00
 3250 ..........54.2 ........... 9.23
 3500 ..........58.3 ........... 8.57
 3750 ..........62.5 ........... 8.00
 4000 ..........66.7 ........... 7.50
 4250 ..........70.8 ........... 7.06
 4500  .........75.0 ........... 6.67
 4750 ..........79.2 ........... 6.32
 5000 ..........83.3 ........... 6.00
 5250 ..........87.5 ........... 5.71
 5500 ..........91.7 ........... 5.45
 5750 ..........95.8 ........... 5.22
 6000 .........100.0 ........... 5.00
 6250 .........104.2 ........... 4.80
 6500 .........108.3 ........... 4.62
 6750 .........112.5 ........... 4.44
 7000 .........116.7 ........... 4.29


OPEN "igntime.dat" FOR OUTPUT AS #1
PRINT #1, " RPM            REV /      180 deg."
PRINT #1, "               SECOND         msec."
PRINT #1,
FOR rpm = 500 TO 7000 STEP 250
PRINT #1, rpm,
rps = rpm / 60
PRINT #1, "  ";
PRINT #1, USING "###.#"; rps;
onerev = 1 / rps
HALFREV = onerev / 2
halfrevMS = HALFREV * 1000
PRINT #1, "       ";
PRINT #1, USING "###.##"; halfrevMS
NEXT rpm
CLOSE

CLS
SHELL "more < igntime.dat"
SYSTEM



Paul Lamar
 
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