kokamo

Hey guys, gals, I am doing a TPI swap into my 73 Nova. It's going on an 11:1 Compression, 30 over 283. I understand pretty much the entire wireing and how sensors and such work but I'm kinda confused to how and what blocklearn is. I don't even know if my computer has it. The TPI unit came out of an 86' trans-am with a 305. The ECM is a 1227165 and it is a mass air flow system.

Can anyone explain what blocklearn is and if I have it in my system.

THANKS!!!

Joe

brutalform

Yes, you do. Block Learn Multiplier, or BLM is a value of 128 in the ECM. At a Block Learn of 128, the system is neither adding , or taking away fuel. 128 is perfect BLM

92'Sleeper

This is the definition of Block Learn in a TPI w/MAP. I'm not sure if it's different with a MAF.

The long term fuel trim (or Block Learn) is a matrix of cells arranged by RPM and Map. Each cell of the long term fuel trim is a register like the short term fuel trim. As the engine operating conditions change, the ECM will switch from cell to cell to determine what "Block Learn Number" factor to use in the base pulse width equation.
While in any given cell, the ECM also monitors the integrator. If the integrator number is far enough from 128, the ECM will change the Block Learn value. Once the long term fuel trim value is changed, it should force the integrator back toward 128.
If the mixture is still not correct (as judged by the Oxygen sensor), the integrator will continue to have a large deviation from the ideal 128. In this case the long term fuel trim value will continue to change until the integrator becomes balanced.
Both Integrator and Block Learn have limits which vary with each PROM. If the mixture is off enough so that long term fuel trim reaches the limit of its control and still cannot correct the condition, the integrator would also go to its limit of control in the same direction. If the mixture is still not corrected by both integrator and block learn at their extreme values, an Oxygen sensor trouble code (DTC) will result.
Under conditions of power enrichment (near WOT), the ECM sets the integrator to 128 and freezes it there until power enrichment is no longer in effect. This is done so the "Closed Loop" factor and Block Learn trim will not try to correct for the commanded richness of power enrichment.

Hope this helps you understand what Block Learn does.

brutalform

Nice work 92' Sleeper. You and I forgot to mention, that a value higher than 128, is lean, and the system adds fuel, and values lower than 128, is rich, and the system takes away fuel.

92'Sleeper

We all forget something until someone else brings us back to reality.

kokamo

Nice, very nice. I am still trying to comprehend most of what you said sleeper, baisically the ecm learns your driving style and compensates for the best air/fuel ratio? is this correct?

Thanks!

Joe

brutalform

I hear ya!

thirdgen88

A more accurate interpretation would be that the ECM learns how your engine in particular performs with the currently programmed configuration.. In closed loop, the engine is always trying to maintain 14.7:1 A/F ratio (certain things will change this such as AE, PE and more, but those are unneeded in this discussion at this point)..