[Gmecm] Re: Piggyback ignition modules

[davesnothereman at netscape.net]

Glad you made some progress.  BTDT with stupid stuff.

Modis exists for us because large source of work and income came up at 
the same time we realized we needed several pieces of equipment 
repaired / replaced.  When really busy, it's sometimes better to spend 
cash.  I tend to be like you, though.  Fix first.

If you can get handy with your hex editor, I've got something for you.  
You'll need to use a 27c256 eprom for your calibration, and you'll need 
to add a few bytes of code to the lower half of the larger chip.  
You'll also have to modify the code in the original binary file.

        ;;;;;;;;;;;;;;;;;;;;;;;
        ;
        ; Notes for adding 6 cylinder compensation to ACMC mask 48:
        ; At 0xFA0E (0X3A0E in a hex editor), replace
        ; ldd L3FC0 (hex string FC3FC0) with jsr L8000
        ; (hex string BD8000).  This will cause code execution to jump to
        ; lower half of 32 kbit eprom.  The following code should be inserted
        ; beginning at 0x8000:
        ;
        ; ldd   L3FC0       ; FC 3F C0
        ; std   *L0033      ; DD 33
        ; ldaa  #0xC0       ; 86 C0<-- this is the compensating value
        ; ldx   #$0033      ; CE 00 33
        ; jsr   LF651       ; BD F6 51
        ; std   *L0033      ; DD 33
        ; lsld          ; 05
        ; rts           ; 39

On the RH side are the hex numbers you'll be adding to the bottoom of 
the larger chip.  The easiest way to do this may be to make 2 .bin 
files.  For the first .bin you need to modify the code in your chip by 
changing the values at 0xFA0E as described above.  Save that file and 
don't get it confused with any of the others.  If you make changes, 
save the new file with a new name, and keep it separate, also.  If you 
use this code without the additional code in the lower half of the 
chip, bad things will happen.

For the second .bin, make a file with 16,384 bytes of 00's.  Then 
replace the first 17 bytes with the values above.  They are FC 3F C0 DD 
33 86 C0 CE 00 33 BD F6 51 DD 33 05 39 .  Program your eprom in 2 
steps, putting the calibration in the "upper" half starting at address 
$4000 and place the file with 17 bytes of custom code in the lower half 
starting at $0000.  Doing it this way will allow you to easily use your 
tuner program to continue to edit calibrations.

There are other ways too.  You could manually "patch" the two files 
together before burning the chip each time you make a new file, or you 
could change the tuner definition file to work with the larger binary 
after the two files are patched together.  Once you get it figured out 
it's just a couple more steps.

I'd recommend not applyiing the EST when trying this for the first 
time.  I'm human and prone to mistakes.  Fuel errors are more forgiving 
than spark errors if I've missed something.  I've done enough checking 
through the code that I'd try it in my car without fear, but with a 
safety net still in place.

Zaphod


-----Original Message-----
From: Andrew Gibson <andrewsharyn at yahoo.com>
To: gmecm at diy-efi.org
Sent: Sat, 25 Mar 2006 07:11:35 -0800 (PST)
Subject: [Gmecm] Re: Piggyback ignition modules

   I figured out what is going on. I accedentally wired the pickup 
backwards to the
module for the ecm. I noticed it because the pickup scope pattern 
looked clean
and even. When I scoped the coil negative wire from the module for the 
ecm the
pattern was bouncing everywhere. I then went to my parts dist from a 
4.3L and
spun it by hand while checking the signal. It was inverted from what I 
had on
the truck. Switched the wires and now it starts easily on both modules 
or I can
hook up just the module for the ecm and get est. (All tables are at 0 
so the
mechanical advances are still running) It runs great! Lesson learned, 
PAY
ATTENTION TO POLARITY ON THE PICKUP COIL AND CRANK SENSORS WHEN WIRING 
CUSTOM
JOBS!

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