[Gmecm] 4 cyl mod for DIS?

[Burgins Auto Service]

Hi,I'm new to the list. While looking at the archives,I noticed there was
some interest in using 4 cyl modules 

for 8 cyl DIS.

I built a working setup several years ago. Combining the two ref signals
with diodes won't work because the

4 cyl refs have a 66% duty cycle. The waveforms overlap causing a high
signal all the time. A logic AND gate

output is only high when both ref signals from the 4 cyl mods overlap
producing a 8 cyl ref output to to the

ECM @ 33% duty cycle.

To toggle the IC signal to the correct module,I used a JK flipflop with ref
from each 4 cyl mod as J and K inputs.

IC was used as the clock input.

The result is is two outputs to the modules @ 50% duty cycle-don't worry
about dwell cause the 4cyl mods

handle that.

You also need a handfull of descretes for circuit protection(reverse
battery,load dump,ect). Also need a

 transistor controlled from bypass to short out IC to avoid setting a code
42(trust me,it won't run without it)

Build your wheel with enough iron to run the mag pickups.

Due to my unique application,I used a dual hall effect pickup with an inner
and outer wheel phased at 90

degrees and differentiated the signals to the modules. Over time,this proved
to be unreliable.

I have since built a microcontoller based DIS that uses a dual wheel with
wider vanes(one with 4 windows

for ref,and one for sync which allows 58 degrees advance and 28 degrees
retard). The programming 

handles coil coil charge time(dwell),tach output,ref signal to the ECM,coil
sequencing,and limited

diagnostics with trouble code display. I used IGBTs with analog current
control plus the programming

to drive the GM DIS coils.

   Marc