[Gmecm] BLM cell confusion

[Gary Evans]

Not Kidding.

If you have some time, check out the disassembly. There are only 3  
cells defined. Unlike the 16 cell code, which determines cell based  
on rpm and map, the $a1 and $88 define the cells based on VSS, BPW  
and MAP.

Here are the definitions in the code:

                   			HIGH HYSTERESIS VALUE, WITH  KLCBPWL
870F        04      4 KCELIDLL 1.3 MPH    IF SPEED EXCEEDS THIS  
THRESHOLD, CAN'T BE IDLE
                           			LOW HYSTERESIS VALUE, WITH KCELIDLH
8710        06      6 KCELIDLH   2 MPH    IF SPEED EXCEEDS THIS  
THRESHOLD, CAN'T BE IDLE
                          			HIGH HYSTERESIS VALUE, WITH KCELIDLL
8711        24     36 KCELMAPL 31.3 KPA    DIVIDING POINT BETWEEN  
PART THROTTLE CELL AND
						OVERRUN CELL LOW HYSTERESIS VALUE, WITH KCELMAPH
8712        37     55 KCELMAPH 37.2 KPA    HIGH MAP DETERMINES PART  
THROTTLE CELL
      							HIGH HYSTERESIS VALUE, WITH KCELMAPL
8713      0080    128 KCELBPWL 1.95 MSEC   THRESH BETWEEN CELL 1 AND  
CELL 2
                     			LOW HYSTERESIS VALUE, WITH KCELBPWH
8715      0090    144 KCELBPWH 2.2 MSEC   BPW > THRESH DETERMINES CELL 1
                     			HIGH HYSTERESIS VALUE, WITH KCELBPWL

There are only 3 cells: Idle, part throttle, and overrun.

My scan tool is a laptop reading the raw ALDL stream for the ECM. The  
ECM *never* reports any other cell than 0, 1 or 2. Is it possible the  
Tech 1 is faking 16 cells based on the RPM / MAP values?

As for the 6+1 crank trigger, there have been lengthy threads in the  
past on the differences between the DIS and distributor code. Despite  
the similarities in wiring and theory of operation, the distributor  
and DIS codes expect slightly different things to be happening on the  
signal lines. There is a difference in the timing and dwell  
calculations that no one ever seemed to figure out (or if they did, I  
missed it). Of particular interest is this line:

801B        AA    170 KREFANGL 59.8 DEG SPARK REFERENCE ANGLE

I read about the trials of another GMECM member trying to get DIS to  
run on distributor code, decided it wasn't worth blowing up my  
engine, and went with the $a1 code instead.

This google search will lead you to some of the old threads on the  
subject:

http://www.google.com/search?q=gmecm+dis+distributor+base+reference 
+angle

-Gary


On Nov 13, 2005, at 1:16 PM, WopOnTour wrote:

> Gary
> Nah, you're kidding right? I realize the $88 and $1A calibration  
> details concern itself with cells 0 and 1 a lot for as these are  
> idle cells, but I've had a TECH1 scan tool on hundreds of those V6s  
> and the BLM cell PID varies between cell 3 and cell 15 at road  
> loads. What scan tool do you use??
>
> Also, what difference does the style crank triggering make to the  
> ECM? That's all resolved by the DIS module itself AFAIK (well  
> except on the newer OBDII models where the CKP is hardwired  
> directly to the ECM) On the 122730/727 the ECMs onlly connection to  
> the ignition system is the EST and BYPASS and the ECM doesnt care  
> what triggering methods (distributor or DIS) are being employed, as  
> the CKP is connected to the DIS module not the ECM.
> Please explain
> WopOnTour
>
> ----- Original Message ----- From: "Gary Evans" <gary at garyandliz.com>
> To: <gmecm at diy-efi.org>
> Sent: Sunday, November 13, 2005 1:13 AM
> Subject: Re: [Gmecm] BLM cell confusion
>
>
>> No really, they exist. The $a1 and $88 masks for the 2.8 / 3.1 V6   
>> engines use only 3 cells. There are probably others, used  
>> primarily  on "low budget" applications. The customary masks to  
>> work with ($8d  for example) are performance oriented, so the 16  
>> cell calibrations  are better known in the GMECM community but 16  
>> cells are by no means  standard across all applications.
>>
>> If I was going to start from scratch on my project again, I would  
>> definitely try to use one of the other masks that offer the usual  
>> 16  BLM cells. IMHO, the $a1 and $88 code bases are sloppily  
>> written and  not very easy to tune. I am no assembly expert, but  
>> from the work I  have done on the $a1 hac, the code appears to be  
>> a mess. Example: the  injector constant is part of one of the EGR  
>> tables. yeah.....
>>
>> However, I need the 6+1 crank trigger DIS, and as far is I know  
>> $88  $8F and $A1 are the only masks that support it out of the box  
>> on the  V6. If there is another mask that supports 6+1 crank  
>> trigger, DIS,  *and* 16 BLM cells, I would love to hear about it  
>> because I am  getting the itch to do more tuning on my car, and I  
>> might be inclined  to try something new if it offered better  
>> tunability and cleaner (or  maybe just better documented) code.
>>
>> -Gary
>>
>>
>> On Nov 12, 2005, at 9:05 PM, WopOnTour wrote:
>>
>>> Gary
>>> This post has me a bit stumped
>>> What about the other 13 cells?
>>> Don't ALL of the OBDI calibrations use at least a full 16 cell  
>>> BLM  map? (4cells by 4cells) Cells 0 thru 16 ??
>>> I know some others like the Quad4 ECMs use 16 PLUS and additional  
>>> 4 cells (17-20) that depend on "in-gear" state and AC clutch status.
>>> I've never heard of a GM calibration with only 3 cells...
>>> WopOnTour
>>
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