I believe it was you Glen? that in a past post had mentioned that you were trying adjusting the "spread" of the cells? I'd just like to know if there are any advantages that you found with changing them. Thanks.

 

On SD cars the BLM cells deliniated differently than MAF. With SD it is based on RPM & Load (MAP), while MAF uses RPM & Air Flow (gms/sec) IIRC.

On my SD car, altering the boundary edges definitely helped in using more of the cells of the BLM table which made driveability better. It has more "typical operating conditions" that it can store and use in the cells. Which helps the ECM "zero in" on the proper fuel trim quicker.

With the stock settings for the edge boundaries, there were a lot of cells I just never "hit", thus they were basically useless to me. While the cells that were hit had a very "broad" range. This meant that if I was at the lower "edge" of the cell I would get one BLM reading while at the higher "edge" (while remaining in the same cell) I got a different reading. This makes the ECM has to take some time to "trim" based on the O2 sensor corrections. Imagine how useless the BLM would be if ALL the values were stored in the same cell. Basically, the ECM would have to rely on the O2 sensor for all fuel triims.

Altering the edges so I am using more cells (so each individual cell has a narrower range) means the ECM will have a better chance of having the correct trim already stored in the BLM cell.

I am still reviewing the code to find out EXACTLY what the Block Learn Mode truly does. But using as many of the cells as possible definitely helps to ensure the BLM has a useful value in a particular cell. But, some cells are impossible to hit because the RPM/Load (or Air Flow for MAF) never occur.

Like very low rpms (just off idle) with a high load (SD) or high air flow (MAF). With an SD auto car, the TC would stall and take me to the "next edge boudary" if I were to hold the brake and put a load on the engine. Same for MAF cars, I can't see how you could be in the lowest RPM level at the hghest air flow.

I believe that this is an area where you need to tailor the boudary edges to you typical driving style and your car. A car with 2.73s should have a lower rpm boundary for the highest "row" while a car with 3.73s should have a higher rpm boundary as they will see more rpms at "high cruising speeds".

Ditto with driving style. If you typically are doing 80-85 mph on "highway cruise" you'd want a higher RPM boundary while if you seldom exceed 70 mph in "highway cruise", you might prefer to lower the rpm level as you will seldom ever use the top most row in your driving.

 

Thanks for the info!