One of the most ubiquitous ignition systems on the planet.
Very popular with the Megasquirt crowd.

Old message:
"I'm investigating using two Ford EDIS ignition controllers.
They will work without computer input, set for 10 degrees
of advance. It just needs a power source and input from
a vr sensor. In normal operation, the computer sends
a correction signal that the controller uses to change
the spark advance. "

snips...

"The EDIS system requires a 36-1 wheel (36 teeth with 1 missing).
I'm thinking that one of the old bicycles that my boys never
use may end up missing a chain sprocket. (As a nod to the
original homebuilders, I think every homebuilt airplane
should include at least one bicycle part.)"


Enerst Christley

I think we can get along with one module and a
four cylinder two coil pack firing 4 plugs.

One coil can fire both leading and trailing
plugs using the four cylinder module.
Early version (DIS) are the most suitable as it uses
HE's to fire and is stand alone.
Does not need a computer.

Later ones (EDIS) use a mag pick and require a special
trigger wheel.

The six cylinder module can be used with a 3
rotor.

I am going to get one and test it.

---------------------------------------------------------

When you start to study the history of electronic
ignitions systems certain patterns and ideas
start to emerge. Ford patented the DIS system
back in 1990. The way the Ford EDIS system works for
a four cylinder or a two rotor is; a counter is preset
with the 1/2 the number teeth on the trigger wheel.
The computer goes away and does something else.
When the count is reached the computer is sent
a hardware interrupt telling it is time to fire
rotor 2 or the next set of cylinders.
This works over a wide RPM range.

The same scheme will work with a 3 rotor
or a 6 cylinder engine. The Ford used a missing
tooth detector so only one mag pickup was needed.

The 2nd gen Mazda RX7 CAS probably used the same
idea but there was no missing teeth and it
had two mag pickups. One gave a single
pulse at 20 degrees BTDC or so and the other
sent out a wave train of pulses that could be
counted. The mag pickups  were/are called VR's.

That is why the 3 rotor could use the same CAS
as the 2 rotor. Just a different number was loaded
into the counter. Just about all single
chips computers have this type of hardware counter.

The drawback to these schemes is the timing is
not all that accurate. Especially the 2nd gen
as it does not have many teeth. The Ford
uses 36 teeth a number divisible by 2 or 3 giving
a whole number in both cases so it can be used with
a 4 or 6 cyl. engine.

I suspect Tracy is doing the same thing with
all of his systems.

Paul Lamar