Peter Nunn wrote:

Sorry guys, confused again.....
Looked at my engine, always a bad idea when tring to work things out...
The sensor has 2 sensors, 1 lower with 24 teeth around it therefore

there

are 15 degrees between the teeth, I presume this is used to generate the
primary firing signal, the upper sensor has two teeth presumably to mark

the

'top dead center' of the first chamber.

This  would indicate that for 2 rotors there are 12 fire signals per 180
degrees of distributor rotation or that there is 6 fire signals per

rotor

per 180 degrees, or 2 rotor revolutions per 180 degrees of distributor
rotation, or 4 rotor revolutions per 1 revolution of the distributor.

This means that the distributor ratio is not 1:2 but must be 6:1 to give

a

4:1 ratio between the rotor rotation and the distributor rotation?
I cannot see how else the timing signals can be generated from the

sensors?

Any ideas out there ?

Computers are good at math so all they need know is the position of the

e-shaft

and RPM at any moment in time and they can figure out when to fire the

spark plugs

within several microseconds. The late engines have done away with the

crank

angle sensor and there are only two sensors on the e-shaft with a bunch of
holes in a steel plate.

The fundamental mechanical thing about the two rotor Wankel is it fires

twice per

rev regardless of what the sensors imply. It may fire more and that is

called a lost spark system. It is sometimes cheaper to do that with some coil
setups  but it waste electrical energy.

Paul Lamar

Tracy Crook wrote:

In following this discussion on timing I keep asking myself, "what is the
end goal of the investigation?"  Are you trying to build an ignition system
or what?  If this is the case,  Paul is right.  Computers are needed to do
the job.  The Mazda crank angle sensor with two points on it puts out a
pulse indicating when rotor 1 is at about 30 degrees BTDC.  The other sensor
with 24 points gives a pulse every 30 degrees of crankshaft rotation.
That's all you get.  Timing for the other rotor must be derived from this
information.  Its also up to the computer to calculate the advance and
retard for spark timing since there is no centrifugal or vacuum advance
mechanism.

Tracy Crook
rws@altavista.net
www.rotaryaviation.com

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