Hello and Thanks for the great info so far!
I have been data logging and analyizing in anticipation of receiving my Autoprom and related goods (including WideBand O2) next week. I am climbing this good steep learning curve and have found great answers to my most of the questions I have had. I am tunning a 1991 Chevy Suburban with a 16147060. I swaped in a 383 w/ Holley TBI and LT1 style roller cam, and roller rockers and headers. I have a chip from Brian at TBIChips - actually I am on my second chip from him after datalogging. Holley TBI fuel pressure is about 12 1/4psi.
My question comes from the behavior of my BLM cells and my O2 sensor. My low to mid KPA BLM are showing right around or just above 100 (WOT seem better). My O2 sensor has been very erratic but mostly in the 800 - 900 range. The motor does not seem too rich, but the data shows otherwise. It does smell a bit rich when cold. It runs pretty good and is in closed loop. Spark plugs look OK. I am trying to understand if the BLM numbers are mainly influenced by the O2 readings or from other factors. Everything I read states that O2 readings are inacurate at other than ideal settings. If this is true how can they influence the BLM numbers? How else would the BLM know if the engine is rich or lean? Could my program just be so far off that the O2 is out of wack and the BLMs are going to low 100 range?
In short my question is more theoretical than specific to my truck: What influences the BLM and INT numbers?
I can post data log later if I figure out how.

Thanks much,
Keith

 

Basically there is a window that the O2 sensor value needs to be within. Once ouside of this window for a long enough time the INTegrator will start to move. Once the INT moves far enough from 128 for a long enough period of time the BLM will start to move.

Under the '8063/'8746/'7747 section of the Tuning Guide Book sticky is a fueling logic write up. Explains this and a bunch more.

RBob.

 

I will dig into that write-up, Thanks.
I have another basic question: At some point did GM eliminate the use of VE1 & VE2 and just go with a single VE table? The reason I ask is that when looking at Tunerpro I can only find a single VE table (for my 1614706 w/ a $85).

thanks again,
Keith

 

They did move away from the 'adder' table concept. Which is a good move. Although it was still used up to '94 or so in some masks (even MPFI stuff used adder tables, $88, $A1).

It looks like the $85 mask has only the one VE table.

What GM also did was to use several VE tables. Along the lines of a low speed and a high speed table. Sometimes the low speed table was an idle table. Then a different VE table was used during open throttle at low engine speeds. Then a third table once the RPM exceeded 2K or 2.4K RPM.

RBob.

 

Wow! I am about 3/4 way through the Fuel Logic article that you referenced and it is very informative, if not a bit over my head (a good thing). I love learning this stuff and having those minor eppifanies where things start to click.