I've pretty much done all I can without getting into fuel and spark control. I have read many posts that refer to BLM, INT, and VE. I know what these letters stand for, but that's about it. I read my factory shop manual twice (section 6E and 6E3) and could not find an explanation of these terms, or how they are used. I gather that information on these is available on diy-efi, but I could not find it. I see no such values in my TunerCat software, so I don't know if I could do anything with them anyway. Since mine is a TPI with MAF, does a VE table even exist? Where do I go to learn about this stuff?

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'87 IROC 5.7l TPI - original owner!

 

BLM = Block Learn Modifier. This value is the long term correction factor used by the ECM to modify the fuel sprayed. Divide this number by 128 to get the actual ratio of fuel modification. A value of 128 indicates that the ECM does not need to make any corrections to the fueling.

INT = Integrator. This is the short term correction factor applied to the fuel by the ECM. When the integrator is at 128, the BLM value is stable and considered 'learned'.

VE = Volumetric Efficiency. This term represents how efficient the engine is at pumping air. A higher number indicates a more efficient engine, which in turn means more fuel is required. Typically, speed density computer systems use a VE table, while MAF systems do not.

Since mine is a TPI with MAF, does a VE table even exist?

Nope.

Nick

 

Nick,

No, the MAF equipped cars do not use VE tables. Rather, they utilize 6 MAF scalar tables that indicate the grams/second airflow vs. counts. The MAF generates counts and then correlates the counts to the MAF scalar tables to determine how much air (grams/second) is entering the engine. IMHO, this is one of the reasons that the 165 is harder to adjust. With Speed Density you have a correlation point ... this point is RPMs vs. MAP (kPa). Find this point in the 3D table and then adjust accordingly. With MAF its different. You can get a value via a scan tool for grams/second. However, then you have to adjust the MAF scalars in THAT g/sec region. IMHO this involves a tad bit more guesswork.

BTW - good coverage of BLM, INT, and VE.

Tim

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• Program your own PROMs!. Read my article to get started!
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TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
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