How does the S-AFC adjust fuel? Why does it need the TPS and RPM signals?
By intercepting the MAF or MAP sensor voltage, and modifying it, the S-AFC tricks the ECU into thinking that there is either more or less air going into the engine than there really is. In theory, the ECU will blindly add or subtract the appropriate amount of fuel to compensate. The S-AFC uses the TPS and RPM signals to allow the tuner to set specific operating regions where fuel is to be added or subtracted. Unfortunately, this is a rather oversimplified method of doing things, since ideally one would also be interested in knowing about engine load and/or boost (for forced induction applications).
