158 Fuel Control Learning Adaptation Values Long-Term Fuel Control is adding directly to the injector opening time for all memory cells. However, data is only updated under certain idle conditions. Be aware that Idle and Part Load Multiplicative work together to establish the long term FT. C.1.2 Multiplicative Adaptation Multiplicative means multiplying or taking the preprogrammed cell base value and multiplying that number by either a correction factor or percent. Here, the correction amount increased or decreased in each memory block cell is dependent on each cell’s base injection pulse. This form of adaptation is required to compensate for fuel control-type problems that get worse with increased engine speed (i.e., a faulty injector. Short term FT in VW/Audi language is usually called O regulation or O control. The readings are constantly changing, directly responding to oxygen sensor (OS) input. Normal readings are usually in the ±10% range with 0 as the midpoint. If it gets too far off, Long-term additive or multiplicative adjusts the window back to the midpoint balanced state). Multiplicative adaptation correction indicates the long-term FT correction that the ECM is applying to the air/fuel mixture during closed loop operation over the middle to upper range of engine operation. VW/Audi use the term Multiplicative Mixture Adaptation because it is a percent correction factor based on the individual base injection value for each memory cell. Cells are constantly updated based on feedback operation. If any cell stores an update that is beyond the neutral feedback value, a correction is then factored into the injector pulse-width calculation. To maintain the optimal air/fuel ratio of 14.7:1 for catalytic converter (CAT) efficiency, the ECM monitors the O2Ss and calculated load. From this information, the ECM calculates a percent value that indicates how much to enrich or dilute the fuel mixture. Sometimes, the ECM makes fine tuning adjustments across the complete fuel map by adjusting the IDLE (Additive) FUEL TRIM (for example, when a fine adjustment is needed across the range to compensate for fuel injector drift).