DIS, HEI, and PITAs

[Tedscj at aol.com]

I Tried some things with the DIS today.
First, I made sure the DIS was at least responding to the original DIS .bin 
(from a '91 Sunbird) and it was.

Then I just started from the beginning trying to adjust different things with 
the SyTy .bin.  I kept notes and I will paste them right here.

 The changes I made to the .bin were NOT accumulative.  The changes made were 
ONLY those mentioned in each line.  Except for the Main Spark Table.  1-5 the 
table was zeroed out completely  6< the table was 0 for everything below 
2000rpm and 30degrees for everything above 2000rpm (so that any advance would 
be obvious.)

1 - 5 : Main Spark Table zeroed out.

1. no changes except for above:   ran about 60 degrees advanced.
2  KREFANGL at 40:  No difference.
3. MAXRTRD2 at 50:  Timing mark right at zero.
4. MAXRTRD2 at 70:  Timing mark at 20 BTDC.
MAXRTRD2 seems to be ADVANCING the base timing.
5. Changed KCTBIAS (coolant temp bias) from 20 to 50:  No changed.

6-     Main spark advance table set as described below.

6.  Changed main spark advance to abruptly go from 0 to 30 degrees advance at 
2000 rpm:  It DID advance abruptly at 2000 RPM.
7.  set MAXRTRD2 at 60:  timing mark at 10 BTDC but there is now NO advance 
at 2000RPM
8.  7 + changed MAXADVN2 from 46 to 120:  still No advance at 2000 RPM
9.  change MAXRTRD2 to 5 (to check if a small change will still render the 
main spark table inop.):  It DID advance abruptly at 2000RPM.  SO changing 
the MAXRTRD2 value does not in itself render the the Main Spark Adv. inop.
10.  Change MAXRTRD2 to 20 (I'm going to sneak up on the 60 value):  Can 
barely get the car started at 20, and won't reve pas 1200 or so ... will jump 
to 40 and see what happens.
11.  MAXRTRD2 set to 40:  Timing mark at something like 10 ATDC and there is 
NO advance after 2000RPM.
12.  Set MAXRTRD2 to 50 and set MAXADVN2 to 0.0 just to see what happens:  
timing mark at 0 degrees and No advance.
13.  leave MAXRTRD2 at 50 and move MAXADVN2 to 60 and KREFANGL to 60 to see 
what happens:  Still no advance.
14.  same as above only MAXADVN2 at 120:  still no advance.

What did I learn?
The DIS module DOES respond to the EST signal, WHEN no other parameters have 
been changed too far.  The MAXRTRD2 seems to advance the base timing.  The 
MAXADVN2 and KREFANGL seem to have no apparent effect.  Once you advance the 
base timing too far (through the MAXRTRD2) the MAIN SPARK TABLE ceases to be 
effective.  Again, adjusting the MAXADVN2 does not solve this problem and 
appears to have no effect.
You can see all the different combinations I have tried above.  If you can 
think of anything else, please let me know.
Thanks,
Ted

PS  What Bruce and Terry said about inverting the Reference Signal from the 
DIS to the ECM would work.  It would push back the timing 60degrees (assuming 
50% duty cylce and three pulse per revolution).  That would set the base 
timing at 10degrees when the Main Spark Table says 0 degrees, which is close 
enough.  And I found that if you don't mess with the KREFANGL, MAXRTRD2, or 
MAXADVN2 then the DIS module WILL respond to the EST signal.  If you set the 
base timing too far with the MAXRTRD2, then the DIS module will NOT respond 
to the EST signal (or maybe the ECM stops pushing up the advance on the EST 
signal any further).