The Apexi SAFC or Super Airflow Converter is a reed adjusting device that is used in conjunction with the Engine Control Action Unit or ECU (for its acronym in English). The SAFC modifies the oxygen sensor signal which is constantly monitored by the ECU. When this signal indicates a change in oxygen levels, the ECU compensates itself by increasing or decreasing fuel levels accordingly. With a suitable melody, the Apexi SAFC improves the performance and reliability of your modified engine.
Adjust the SAFC fuel baseline correction values, if your engine is equipped with modified injectors. This is necessary to compensate for the increased flow rate of the injectors, compared to stock units. Determine the percentage increase in the flow of the injectors by dividing the value of the flow rate of the modified injectors by the value of the existence of flow velocity. Enter this percentage as a negative value for all rpm increments in the SAFC “Hi-Thrtl” and “Lo-Thrtl” menus.
Use an ECU diagnostic cable to connect a data logger device to the ECU access port. This port is commonly found under the driver’s side dashboard area on the inside. Once connected, the data logger is able to record the different diagnostics of the engines controlled by the ECU.
Set the data logger to record the value of the engine air-fuel ratio. This allows you to determine the SAFC fuel correction value necessary to achieve a perfect air-fuel ratio. Although the stoichiometric ratio for internal combustion engines is 14.7 to 1, a richer value is needed for optimum performance and reliability. For naturally aspirated engines, the optimum air-fuel ratio is approximately 13.5-to-1, while forced induction engines respond best to a ratio of approximately 11.5-to 1.
Drive your vehicle to a place where you can safely rev the engine to its red line rpm. Make sure the data logger is activated, then rev the engine to full throttle. You should get an air-fuel ratio reading for the entire rpm band, so accelerate from about 2,000 rpm until the engine reaches its red-line rpm value.
Observe the air-fuel ratio values recorded by the data logger, after the vehicle has been safely parked. Compare these values with the optimal ratio for your engine. Values greater than the optimum value indicate an excessively lean air-to-fuel ratio, while values less than the optimum value indicate an excessively rich ratio.
Use the “Hi-Thrtl” menu option in the SAFC to enter the fuel correction percentages for all rpm increments. Increases the percentages of correction of rpm values, where the air-fuel ratio was greater than the optimal ratio. This will increase the fuel flow to the rpm values, thus balancing the air-fuel ratio. Similarly, it decreases the SAFC fuel correction percentages to the rpm values, where the air-fuel ratio was less than the optimum ratio.
Repeat the process to record another data logging session. Use the air-fuel ratio data from the second session to further refine the engine’s fuel curve with the SAFC. After several tuning sessions, you will find that the air-fuel ratio remains close to the consistent optimum value throughout the rpm band. This indicates that your engine is optimally tuned for performance and reliability.
Tips
Entering a correction value that is too high in the Apexi SAFC can increase or decrease fuel flow to such an extent that it damages the engine. To avoid this, never change the SAFC correction values by more than 5 percent at a time. By entering correction values in small increments, you will be able to safely improve your engine performance throughout multiple tuning sessions.
