Hey all,

Been thinking about this for a while and thought I'd put it out there to the brain trust.

What is ur preferred procedure for datalogging when introducing a new bin file. In particular, I am thinking of the VE tables and the accuracy of the new log. We have 3 options:

1. Install new cal and datalog
2. Install new cal, clear ECM and datalog w clean BLM slate
3. Install new cal, clear ECM or not, then drive around, THEN begin datalog.

Curious to see what any of u prefer and why? Or perhaps none of that matters.

 

I guess it depends...

If I'm just making a tweak to one area of the VE table, there's no need to have the ECM re-learn everything. I just let it relearn that one targeted area and display the results of the changes.

However, if say, I've made a drastic engine modification (new cam, different intake, etc), or I've changed injectors, etc, I'll probably reset the ECM and start fresh.

 

UL,

I am currently re-doing the VE tables as a consequence of the issues I discovered with oil seepage and defective injectors.
My most recent datalog is demonstrating a nearly universal rich mixture making up the previous tune. Oil consumption and knock counts have been nearly eliminated.

 

Interesting question. I've always looked at it this way. The ECM is constantly learning once certain temperature and other conditions are met. It is never satisfied. Anything the ECM code learns, it stores away in variables or NVRAM for a future use in (milliseconds later or at key off for next start-up). When logging, we are not seeing the learned values but what's happening in real time. That would say that clearing the ECM has no effect on what we see in logs and thus does not affect the results. Perhaps not the same on newer cars (OBDII) where electronic transmission shift points are saved based on driving habits, etc..

However, having said that, consider me paranoid, I have a power switch to my ECM. Always turn it off before a new cal. Switch also a great theft preventer

See also this from Diamond Star Motors (DSM in the article) regarding the question: http://www.technomotive.com/theory/myth/ecureset.htm

 

Yeah, I guess it comes down to this. You either start at “neutral” w a reset, or use the baseline from the previous calibration. So when datalogging and then calcing the changes to ur VE, either method has its own bias value built into it. I guess u need a log long enough to essentially negate that bias coming from the previous cal or a reset.

 

Some calibrations have a key-on init value for the BLMs. Can set those to 128. As an aside, the '8746 ($61) has this hard-coded.

RBob.

 

Thx RBob. Would that be ur preferred method of starting a new log on a revised cal? I don’t see that flag on the $D0 mask.

 

My preference after making VE changes is to set the BLM values to 128 (at key-on). The EBL systems have this feature.

I checked $D0 and didn't see it either. There is likely a mode 4 command that will do that.

RBob.

 

RBob,

I did find it in one of the def files I have. In $D0 its at x018. Do u use it just while tuning or leave it permanently? Something like this would be nice when tuning since I would not need to reset the damn radio and clock each time.

 

Ah, so it is an option flag... I tend to leave it to reset to 128 on every power up.

RBob.

 

Thx Rbob.

 

Thx Rbob