[Second Series]

In order to decifer winALDL an understanding of what is happening is necessary.
I have been reading about the ALDL and the EFI system. I have summarized some of that here.

There are three operating modes, Closed loop mode, Open loop mode, and Power Enrichment mode.

The engine runs in Open loop mode when it is started, when idling, or when engine load increases. The O2 sensor is ignored. In open loop, the ECM commands an A/F ratio that is determined from a table of A/F vs. engine coolant temperature.

In Closed Loop, the PCM takes dozens of readings from the O2 sensors each second and uses that data to fine-tune the amount of open time the injectors are on. The MAP, Temp, and RPM are used to make a base fuel guess, then the O2 sensors give the PCM feedback on how well it has guessed, and it adjusts to maintain an Air/Fuel ratio of 14.7:1. This is the value that allows a catalytic converter to reduce exhaust emissions most efficiently. This is also the value that typical O2 sensors are most accurate at. O2 sensors start to work above 300 degrees or 600mv. The A/F has a value of 1 in the equation during Closed loop mode.

Power Enrichment mode is with wide open throttle. The O2 sensor is ignored and the TPS is used to determine the A/F ratio.

There is an equation used to determine the Base Pulse Width of the injector.
BPW = BPC * MAP * T * A/F * VE * BVC * BLM * DFCO * DE * CLT * TBM

Let’s look at how this equation relates to the values in winALDL.
winALDL shows several readings. IAC, Coolant Temp, Speed, MAP, RPM, TPS, INT, O2, Battery Voltage, Knock counter, BLM, rich/lean to name a few.

BPC, Base Pulse Constant is calculated from the volume of one cylinder, the flow rate of one injector, and a constant.

MAP, Manifold Absolute Pressure, that value can be seen in winALDL.

T in this equation is the inverse of the absolute temperature.

A/F may be the O2 reading in winALDL. (The value that I got at idle was around 0.45).

VE, Volumetric Efficiency, VE is an important factor in the equation that corrects for different engine efficiencies. It is based on a table of RPM and MAP conditions. This table can be modified to tune the chip.

Battery Voltage Correction. This term is a correction to offset the change in injector response due to battery voltage fluctuations.

The BLOCK LEARN term can be viewed as a semi-permanent automatic adjustment of the VE tables. If you disconnect the battery, the BLM adjustments revert back to 128 or neutral (the neutral value for a BLM value is 128). Another name for the BLOCK LEARN term is long term fuel trim. Over time, the BLM numbers will settle at a value that gives a 14.7 A/F ratio with no closed loop term correction. There are more than one BLM value, unlike the single Integrator. The BLM can be up to 32 different numbers depending on the ECM model. The Block Learn term derives its name from the way the VE table is divided into blocks for the corrections to take place. A cell value of 128 is neutral, no fuel is added or subtracted. A cell value below 128 is rich, A cell value above 128 is lean. (The value that I got at idle was 128 and that indicated it was in open loop mode).

INT is shown in winALDL. In closed loop, it is discussed how the Integrator increases or decreases as the ECM gets feedack from the O2 sensor. The 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. As the BLM rises, it begins to effect the AFR because the VE table is being increased. As the AFR drops (gets richer) in response to the increased VE table, the Integrator will stop rising and begin to fall. Once the Integrator returns to a value of 128, the BLM will stop moving. Not only will the BLM stop moving, it will remain at that value permanently, essentially retuning the VE table at this engine operating condition.
If the BLMs are both above and below 128, but not too far above (135) and below (120), your VE table is probably reasonably close. If your BLMs are way above and below 128 all over the VE tables, the calibration is probably significantly off and needs to be manually corrected in the chip with an EPROM burner.

DFCO, DECEL FUEL CUTOFF. When you take your foot off the gas pedal going downhill or decelerating quickly, the ECM will cut off the fuel entirely.

DE, DECEL FUEL ENLEANMENT allows some fuel to continue.

CLT, CLOSED LOOP, or short term fuel trim is when feedback from the O2 sensor is used to make corrections to the air fuel ratio. The ECM makes immediate but temporary corrections to the fuel delivery to maintain the AFR at 14.7. The short term fuel trim value is called the Integrator in most early scantools. The value of the integrator varies above and below 128 with 128 being no correction. For ex., if the Integrator is 140, the ECM is adding fuel because the O2 sesnor is reading a lean mixture. If the Integrator is 115, the ECM is removing fuel because the O2 sensor is reading a rich mixture. Anytime the system is not in closed loop, the Integrator will immediately return to a value of 128 and stay there. There is only one Integrator and its value is solely dependent on the O2 sensor. When the engine is started, the ECM will keep the Integrator at 128 until the ECM determines that the O2 sensor is working correctly and that the engine temperature and time delay constraints before entering closed loop have been satisfied. Once the ECM goes into closed loop, the Integrator begins to adjust the fuel delivery to maintain a 14.7 A/F ratio, however, the Integrator term is only weighted half as much as the Block Learn term. The Integrator and BLOCK LEARN work together to re-tune the system to match any engine's charactersitics, up to a practical limit.

TBM, TURBO BOOST MULTIPLIER is for when a turbo is used.

Because of the slow data rate, 160 baud, the O2 sensor voltage is meaningless unless it shows stuck at the same voltage all the time. The normal behavior of the O2 sensor is to cycle rapidly, 2-3 times a second, from rich to lean.

The biggest benefit to WinALDL aside from the normal scantool functions is to log data while driving, particularly the BLM and INT numbers. Over time you can begin to see rich or lean conditions at various throttle/load conditions, and if they're significant you can modify the fuel tables in a new chip and tune your motor that way.

I wish there was a source for this information, but it is just what someone said on the net.

I found most of this on sites about tuning or setting up EFI on an originally carbed engine. The first step is to make sure the timing is correct, use a timing light. The next step is to set the minimum idle, disable the AIC during that procedure. Measure the min and max TPS voltage with a volt meter, plug these values into the boxes on the Configuration page of winALDL. With the correct ECM Type, Com Port, and Baud settings data should flow. There are only Two options for Baud rate, 2400 and 4800. My truck is a 1988 model and supposedly 160 Baud, but my winALDL works with the Baud rate set to 4800. I’ll use the default settings for RPM and MAP range for ‘Narrow’ until I see a reason to change these.

Now it’s time to log some data. The truck should be at operating temperature. Turn on the data logger and drive for 10 to 30 minutes or longer. I had my data tabs set to Narrow Latest, I think Wide Avg might be a better option. I’ll try some different settings. After driving for awhile the BLM, INT, and O2 grids should be full of data. That is what you look at to determine if anything is off and what to change to tune a new chip.
My ‘88’k2500 project is not on the road, so I’ll wait until it is to log data there. I do have a ’90 k1500 that will work as a test subject. I just need to find some time and get it done. I’ll post some logs when I can get to it.