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airflow converter (AFC) only warps the maf signal which tricks the ECU into thinking the engine is moving less air than it really is, so you can use larger injectors. AFC does not make sense to use without installing large injectors. It has nothing to do with the selected maf as the hard limitation is FUEL based, i.e. installing a larger maf does not increase the flow of the current injectors.
If you tell the ECU that airflow is REDUCED so you can use larger injectors and make more power, you can tune the a/f ratio pretty well, the AFC is a powerful and simple tool for this purposes. However, because the ECU thinks the airflow is REDUCED, it also assumes that the engine Volumetric efficiency (cylinder fill %) Is reduced, and because of that issue, the AFC causes too much ignition timing advance. That is you get more and more timing as the injectors get larger and the power is increasing. That is the opposite of what should happen and so, it can and will blow a motor if you do not understand the relationship of this phenomenon. This is why AFC has a bad rap and why people say the AFC is not really 'tuning' the engine- they are right. The AFC is not a tuning solution. It is like a band-aid half solution so you can drive the vehicle with the wrong injectors for a while. However if you actually understand the limitation of an AFC and have a clear picture of how the engine will react in terms of timing than it is quite a valuable and useful piece of electronic equipment despite it's limitations. For example if I am strictly drag racing and don't care about fuel economy I could reduce the timing at the CAS significantly which will ruin my economy and engine efficiency possibly causing carbon buildup and other issues... but it would run really well at WOT with the correctly dialed timing now that I've accounted for the SAFC limitation and I can drag race all day without blowing the engine. Another example is a rom tune which has been properly tuned for larger injectors and has been timed properly as well, the AFC could be used to make minor adjustments without influence the timing too much because we started out very close to the originally properly tuned values and only small corrections are needed. The AFC has it's place just not in most peoples hands.
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