Flex fuel timing table

[turbo_bu]

Been looking at using the flex fuel OS to add timing for a dual fuel applications. The truck already has a propane conversion, but unfortunately, there isn't any method for adjusting the timing (other than using the stock gasoline timing). I already looked at using a COS, but this is a 1 MB PCM and doesn't have a COS 5. Also, COS 5 (nitrous) is limited in retarding timing, not advancing.

This brings me to flex fuel OS. One of the flex fuel tables is {B5947} Flex Fuel Spark table. "This table will alter the spark values when Ethanol fuel is being used."

This is a 3D table, but it is in the format of Airflow vs. RPM. My question is related to how much of those values are used based on the % of ethanol? Typically, there is a weighting table (2D) with multiple columns for varing %'s of ethanol. I didn't see it listed in the OS, but was wondering if anyone had played with this or not? My plan was to make a simple square wave function generator to simulate a given % of ethanol when the propane is activated. Was hoping somebody could provide some insight how this table was used.

[turbo_bu]

My guess is that there is another table, something like {B3660 ethanol blend factor} which controls the amount of spark. This would be similar to how the other spark tables work. Examples are: Spark ECT and Coolant Temp Multiplier tables. Also, the Spark IAT and IAT vs. RPM multiplier. I realize that if this is a table which is not supported, then I am probably out of luck. But, if somebody could give me a hint as to the weighting of the table, or how it's setup, that would be great.