First of all, thanks to all of those who have supported me through this project. It has been fun and challenging, but not being able to leave well enough alone, I have embarked on incorporating the timing function of the Sniper EFI into my build. What am I hoping to achieve by this... no clue.. if I were forced to give a reason... I guess I would say because it was there, and life is too short to ponder things that satisfy your curiosity.
So after consulting a lot of people, and getting quite a bit of apparently conflicting advice, I think I figured out the answer to a long-standing question. Why can't I use the dizzy and fool the EFI into thinking it was a crank trigger. In short, I can emulate the signal or the spark distribution, but not both.
A longer explanation is that you need to give the EFI enough warning in order to trigger the ignition based on your timing table. This is a critical angle, and the dizzy can't tell the Sniper when to trigger. And I quote from the manual.
"Once these steps are completed, the rotor will be pointing to the cylinder #1 terminal on the distributor cap (ensure the engine is still at 50 degrees BTDC on the compression stroke on cylinder #1). Note which position this is on the distributor cap."
So this 50-degree angle means that the system gets an idea where the crank is ahead of the trigger event and can do what it needs to do, then trigger the MSD to fire, all this while making sure that the dizzy is pointing in the right cyl.
I hope that makes sense.
Here is an article that helps explain this perhaps a little better.
Crank Pulley Design
I consulted Tom at 02Again, and he is providing a hub, 2 pulleys (one for the accessories and one for A/C) and a trigger mount (which I will have to mod a bit). The trick is to get it all packed in a relatively small space. This is the unit built for an EDIS based system (this type of system has a different wheel design), which is incompatible with the Sniper EFI, but taking the parts from it will allow me to sandwich a fabricated "flying Magnet" style of trigger wheel between the pulleys for the accessories and A/C .
I may have to modify this a bit because my trigger wheel may sit slightly closer or farther away from the front pulley, but all in all, I think I am about 80% of the way there.
Here is a video of AMT machine shop where I get my stuff done. A great resource for those folks who live in Vancouver CA.
Ok so I finally programmed the timing curve into the Sniper. The interesting thing is that the 123 doesn't change vac advance under 2000 RPM whereas the Sniper EFI will. The crank wheel is done. Pictures to come.
Here is the finished pulley and sensor holder.