BL
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Joined: Jan 2001
Posts: 239
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From: Temperance, MI
Car: 88 GTA + Dakota on N20
Engine: 383 4 bolt
Transmission: 700r4
BL
What is BL And what does it do. Sorry this must sound like a stupid question to you tuning gurus but im just starting out at this programing thing.
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Joined: Jul 1999
Posts: 10,907
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From: The Bone Yard
Car: Death Mobile
Engine: 666 c.i.
BL means Block Learn. There is a fair amount of discussion on it in the archives (or older topics) on this board. Do a search on "BLM" on this board and you will find a few posts on it.
As I understand it, the concept is the same on all EFI cars, just the execution is different. On SD cars there is a 4x4 matrix that breaks it into "cells" based on rpm and map. When the ecm gets into a certain boundary based on the rpm and map of the engine, it will use the most recent value in the cell and adjust the BLM up and down from 128. Values lower than 128 indicating an overly rich condition and the ecm leaning it, and values over 128 indicating a lean condition and the ecm will richen it. The BLM value is a "long term" or larger change and the INT is a "short term" or finer change. When the ecm detects a change in the rpm or map value that cause it to "cross a boundary", it will store the value in the the "cell" it was in, provided it meets certain "time" conditions in the eprom. And start with the value in the new "cell" and start from their.
This is an overly simplified view and there are differences between various ecms and EFIs. But this is the general concept.
When it comes to tuning, I limit the BLM from its normal min/max of 108/160 to 128/128. Thus all the adjustments made to the injector pulse width for leaning and richening are reflected in the INT. From the INT values that I get with my scan tool, I then calculate the change I need to make to my VE tables to try and get 128/128.
But do a search on "BLM" and you will find more information on it. Grumpy did an article on it IIRC, but I don't have that link right now. I wish I had a link to Grumpy's web page, but I only have a few "links" to a couple of articles of his. Scope out www.diy-efi.org and check some of the articles there too. Lots of good info if you dig a little.
As I understand it, the concept is the same on all EFI cars, just the execution is different. On SD cars there is a 4x4 matrix that breaks it into "cells" based on rpm and map. When the ecm gets into a certain boundary based on the rpm and map of the engine, it will use the most recent value in the cell and adjust the BLM up and down from 128. Values lower than 128 indicating an overly rich condition and the ecm leaning it, and values over 128 indicating a lean condition and the ecm will richen it. The BLM value is a "long term" or larger change and the INT is a "short term" or finer change. When the ecm detects a change in the rpm or map value that cause it to "cross a boundary", it will store the value in the the "cell" it was in, provided it meets certain "time" conditions in the eprom. And start with the value in the new "cell" and start from their.
This is an overly simplified view and there are differences between various ecms and EFIs. But this is the general concept.
When it comes to tuning, I limit the BLM from its normal min/max of 108/160 to 128/128. Thus all the adjustments made to the injector pulse width for leaning and richening are reflected in the INT. From the INT values that I get with my scan tool, I then calculate the change I need to make to my VE tables to try and get 128/128.
But do a search on "BLM" and you will find more information on it. Grumpy did an article on it IIRC, but I don't have that link right now. I wish I had a link to Grumpy's web page, but I only have a few "links" to a couple of articles of his. Scope out www.diy-efi.org and check some of the articles there too. Lots of good info if you dig a little.