base / advance timing - TBI/TPI with distributor

[Marc Piccioni]

I have been having a discussion with another gear head about how advance 
timing is calcualated from the reference pulse generated in the 
distributor.

Here is how I described it, and would like a reality check.

Pre LS1 small block chevy firing order is 1 8 4 3 6 5 7 2. Firing occurs on 
90 deg. intervals.

Distributor is set for 0 deg (TDC) advance with the timing connector 
unplugged.

Sequence

1)  # 2 cyl comes upto TDC and a reference pulse is generated, the ecm 
loads a count value into a timer register based upon current RPM and lookup 
table value ( a lower value == more advance, higher value == less advance). 

2) timer reaches 0 generates a timer interrupt, ecm issues a fire pulse to 
the ign. module, #1 cyl. fires xx deg BTDC #1.

3) #1 comes upto TDC and another reference pulse is generated, timer is 
reloaded for #8 firing event.




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