There's a lot of questions about how to adjust the fueling VE tables with BLM data so I'm attempting a tutorial to understand the theory. Lots of it takes some practice and understanding of what is happening and how to make adjustments. We have great tools for this starting with TunerPro RT, some great ADX files for differant ECM/PCMs and spreadsheets made by Dave W that really simplifies the task.
So bare with me and let's see if I can explain it.
This will all be done in $0D with BCC BJYL as a starting point. Can be applied to any mask or bin file. But each mask or bin file has to be exact tables including the BLM History Gram made in TunerPro.
$0D has 2 VE fueling tables, one for Idle and one for Off Idle. This tutorial is using the Off Idle.
I'll include a modified $0D ADX with properly built BLM History tables. One cool trick in this ADX is the Idle BLM History table has one extra row at 2000 RPM, the Idle VE table only goes to 1800 RPM, the purpose of this extra row is so BLM data does not clog up the 1800 RPM row with data from all other RPM ranges, so when cutting and pasting Idle BLM, do not include the 2000 RPM row, it's extra data not needed.
VE = Volumetric Efficiency is a term that corrects fueling for different engine efficiencies. An engine is basically an air pump and the better the pump; the more power it can generate. Some engines are better pumps than others at a given RPM and MAP condition are, so this term allows the equation to be calibrated for different engines. It is used in open or closed loop. If perfect will produce 14.7 to 1 AFR without other sensor adjustments. It is the most important thing to get that right first because all other adjustments like AE, PE, DFCO and lean cruise are based off that.
BLM = Block Learn Multiplier. Block Learn Mode term is long term fuel trim. BLM value tracks the Integrator but has a delay. If the Integrator increases so does the BLM, but the BLM lags behind the Integrator. The higher the Integrator climbs above 128, the faster the BLM rises. BLM value affects the VE table by adding fuel above 128 and subtracting fuel below 128.
To start open TunerPro RT, load your bin, xdf and adx files. Find your fueling VE table, in this case it's the off idle. Open the parameter and click on the Graph Icon.
Hold down the right click button and spin graph for a better view.
Before we do any data logging we are going to smooth out the VE table a bit. Why? Well if you look at a number in a cell this is not the number the PCM uses. It is a interpolated number from that cell and four surrounding cells. So if the table is smoother the BLM adjustments made to it will also be smoother.
Set up the Smooth tool from .1 being a huge amount and .9 being a small amount. Normally I use .7 Some rows or columns may need to be clicked twice, like in this table you can see where it is calibrated to strat to loose power at 4400 RPM, spark is the same, just the way GM built it to only give what motor could use, then die of power and force a shift and not over rev.
You may also need to manually smooth some cells by clicking on the corners and dragging them.
Highlight each row and click smooth.
Highlight each column and click smooth.
Here's what the smoothed VE table looks like. Probably easy to understand how adjustments are going to be easier now. Smooth tables are much easier to work with.
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