The attached screen shot shows the BLM averages from a 1227747 TBI engine. BLM's below 128 are rich. BLM's above 128 are lean. Ideally the BLM averages between 123 to 133 are considered good.
Adding fuel pressure generally makes the BLM's go more rich. Reducing fuel pressure generally makes the BLM's go more lean.
Usually the stock Spark Advance Table works well with a stock engine. If the engine is not stock the stock Spark Advance Table will likely need to be optimized.
Passing an emission test for an engine that is not stock, will likely require tuning of both the fuel table and spark advance table.
Tuning for an emission test will likely be successful with the use of an automotive Gas Analyzer; CO. HC, CO2, O2, NO, &NO2.
dave w
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