Help for Newbies on Spark Timing

[WEG1192 at aol.com]

In a message dated 11/22/2000 11:07:21 PM Eastern Standard Time, 
papworth at ichips.intel.com writes:

<< Any circuit that uses a distributor with its own advance mechanism to
 drive the ECM is going to cause the fuel injection events to advance
 along with the timing -- something that doesn't happen normally.
 This probably won't make a lot of practical difference in a batch-fire
 system but is a little "strange".
  >>

Thanks David,

Just so there's no surprises later, I use info I learn on this list to 
improve the profit margins on a small fuel injection business I toy with. 
Thanks for the snubber circuit info, but I only asked because I was trying to 
see if there was cheap way to avoid buying a GM ignition module for $23. I 
was going to write a website but time is a luxury I don't have these days, so 
I'll just summarize what I do here. I took the magnetic pickup coil wires in 
my Jeep's distributor and paralleled them into two different ignition modules 
at once. The stock AMC (Duraspark) module is used to fire the coil and the GM 
module is used to send RPM signals to the ECM. This allows me to control fuel 
with the ECM but leave the spark timing under stock control. I did realize 
that the stock timing controls may "confuse" the ECM's RPM signal, but after 
5 days of driving, no problems found. Keeping a GM module allows me to 
convert over to ECM timing control at a later date, so I think it is the 
better option than the snubber circuit. Besides, the snubber circuit although 
simple, will probably take more than $23 of my time to build anyway. What 
will be worth the effort is converting the AC speed sensor from my cruise 
control system into a digital contact closure signal. I have been guided by 
another list member towards an op-amp but seems Radio Shack doesn't have one 
in the store, so guess I'll have to order one. I want to build a pass through 
device so that the cruise control isn't affected, but I'm concerned that 
grounding one leg of the speed sensor will render the cruise control 
inoperative. I won't know until I try it and see.
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