[Gmecm] Modify $8D to work on MPFI 3.1L DIS engine

[Brendan Patten]

Okay, I want to run the ever popular $8D code on my 1990 Cavalier 3.1L
I have been looking at the stock files for each and this is what I have
found

I am going from $88 code ATMF to $8D AUJP

I think my main problem areas are the ignition control.


The First thing I have done, is compared a $88 Cavalier to a $88 Camaro,
both are 3.1L MPFI, but Camaro uses a distributor, cavalier is DIS
ignition.

This is what I have found different:

Initial Spark Advance: 
F-Body = 9.8 Deg, Cavalier = 59.8 Deg

Initial Time Out Spark Bias: 
F-Body = 0.0 Deg, Cavalier = 35.2 Deg

Main Spark Advance Vs. MAP Vs. RPM

The F-Body has up to 20 degrees more timing in 40kpa 1400 to 1800 rpm,
and an average 12 degrees more timing from 20-55 kpa, 800 to 2800 rpm
80+ KPA areas are within 4 degrees on both vehicles.  Is there a reason
the spark is not cranked up more on the DIS engines?  Or is added some
other way on another table?

Now the questions I have about going to $8D

$8D has a constant: Maximum Spark Advance. - AUJP stock is 41.8 Deg, how
does this value effect if I put Initial Spark Advance at 59.8 Deg?????
There is no MAX SPARK ADVANCE on the $88 to compare it to.

$8D does not have Initial Time Out Spark Bias, this seems to be
something major different between the two $88 vehicles, but no setting
to change on $8D

If I knew better what Initial Time Out Spark Bias does and how it
relates with Initial Spark Advance, I could learn how to go into the
code and find what I need to change.

Anyone know much about the DIS ignition control compared to distributor?


Thanks...

Brendan
www.lt1swap.com