Royce Wise wrote:

Paul, Tracy, Ed, anyone.
How does the rotary ignition timing compare to a piston engine?
Does it fire like a 3  cylinder, 4 cylinder, 6 , or 8, or none of the

above.

Royce

Once per rev for a one rotor and twice per rev for a two rotor
180 degrees apart. It is quite practical to do away with the
crank angle sensor and trigger off the flywheel.
No shafts or bevel gears required. With a four cycle piston engine
you need to know what stroke it is on (compression or exhaust).
You need to look at the 1/2 speed camshaft to figure it out.

Tracy fires both plugs at the same time and 22 BTDC as I recall.
The Stock Mazda computer fires them at different times to minimize
emissions.

Paul Lamar

The [stock] leading spark system provides a spark to both rotors at the

same time.

A spark is provided for each rotor face (3), so when one rotor has

completed

its revolution it will have fired three times or once per eccentric shaft
rev.  With two rotors this makes its twice per eccentric shaft rev as Paul
indicated.

The leading spark catches one rotor in the right position for the
power/combustion stroke and the other is a "waste spark" that catches the
second rotor during its exhaust cycle (so has no effect - a wasted spark).

The [stock] trailing spark plug is slightly more complicated as it can not

use the

"Waste Spark" approach of the leading igntion module and basically has a
separate coil for each rotor.

Ed Anderson

Gordon Robertson wrote:

Ed,  Why can the trailing spark not use the same waste spark principle as
the leading?

Gordon Robertson

Ed is gone for awhile and I have no idea why Mazda did it like that.
Waste spark systems use more electrical energy of course. Probably
a cost compromise on the part of Mazda. I suspect the trailing
plug actually needs more energy to fire the mixture effectively
therefore one coil per trailing plug was used.

In an airplane you would like to keep your battery
up for as long as possible in case of alternator failure. It is
best to use one coil per spark plug and fire it only when needed.
You could turn the trailing plug system off to limp to the nearest
airport.

Paul Lamar

If we wanted to use an OEM ECM would we use a 4 cylinder, 6, or 8?
Royce

Good question. I would have to think about that hard as OEM ECM's
for piston engines assume a trigger from the 1/2 speed camshaft.
A four cyl fires the the same number of times per rev as a 2 rotor
but the cam shaft trigger is only running at half speed. Seems if
you triggered once per rev of the rotary you might get four
sparks instead of only two out of a four cylinder OEM unit.
Perhaps not. Depends on what you mean by OEM. Is it just
the electronics? I suspect one trigger one spark from the
OEM electronics. So you will need two triggers on the two rotor
flywheel.

Too much for my brain :-)

Paul Lamar
 
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