GM TBI fuel injection

Can anyone point me me to a good reference source on GM TBI injection? I'm having a hell of a time getting detailed information about how the system works. I'm an electrical engineer by trade, so I don't need the details to be watered down. The main area I'm really lacking good info is in how the block learn factors are computed and applied. Somewhere the engineers at GM must have created a flow chart showing how the ECM software works.

Short of the total detail I want, maybe someone can answer these questions for me. How many VE table entries are there? Are the RPM and MAP ranges programmable, or just the values inside? Is there one BLM value for each VE table cell (or fewer or more)?

I'm trying to understand why getting the VE table perfect seems so critical to everyone. On the surface, it would seem that if the engine would at least start, assuming there was one BLM for each cell, that the system would eventually compensate itself and everything would be perfect (as long as you didn't disconnect the battery). If you had a dyno and a laptop, you could go to each cell and dwell there for a minute to let the BLM settle out. What am I missing?

Reply to
Charles
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I started to do some research on this subject a while back, here's a website that has some info:

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Regarding the tables, IIRC there are issues when transitioning from one cell to the next on the short and long term fuel trim. If the changes are too far off of the hard-coded values there will be hesitations and such, but it's been too long since I read that particular subject.

Also, it might help to do your search on the ECM part number, since there were, and are, several different ECM's being used for GM's TBI systems.

JazzMan

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Reply to
JazzMan

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