Coil spark rate or rotary vs piston engine

[Quinton McCombs]

First of all, let me appologize for starting another thread concerning
how often a rotary engine fires....

I just instaled an aftermarket ignition system on my two rotor engine
(13b). One of the installation steps was to configure the system for
the number of cylinders.  It needs this information because it will
change its behavior above 3k RPMs.  The only input that it has it the
trigger to the coil.

In order to decide how to set it, I decided that I needed to figure
out how the Sparks/revolution (crank or eccentric shaft) compared
between the two engines.  the numbers that I came up with don't make
sense and I am hoping that someone can tell me where my logic has
failed me.

I am under the assumption that in a piston engine, each cylinder will
fire once for every two revolutions of the crank shaft.

I am also under the assumption that in a rotary engine, the leading
plug (and trailing short afterwards) will fire twice for every three
revolutions of the eccentric shaft.

Yet another assumtion is that both rotors fire at exactly the same
time.  I have come to this conclusion by the fact that I have one
coild with two leads for the leading plugs.  There is one trigger for
the coil and no distributor.

Given my assumptions, a coil on a piston engine (assuming one coil for
all cylinders) will have spark / minute = RPM * Cylinders * 0.5

According to the formula above the table below shows the number of
sparks per minute for 4, 6, and 8 cylinder engines.

4 cyl    6000 RPM   12000 SPM
6 cyl    6000 RPM   18000 SPM
8 cyl    6000 RPM   24000 SPM

Given my assumptions for the rotary engine the table below should
describe the saprks per minute for 1 and 2 rotor engines.

1 rotor  6000 RPM   4000 SPM
2 rotor  6000 RPM   8000 SPM

Since one trigger pulse will fire both rotors, the aftermarket
ignition system will only see 4000 pulses per minute at 6000 RPM.  I
think this is equiv to a 4 cyl piston engine running at 3000 RPM.

Have I made a mistake in my calculations??????

-Quinton                          mailto:quintonm at bellsouth.net


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-Quinton                            mailto:quintonm at bellsouth.net