straight out of the powerfc faq;
Considerations before use
28. # Apexi SAFC vs Apexi PowerFC, whats the difference?
http://paulr33.skylinesaustralia.com/docs/...erfc-faq.htm#58
Apexi SAFC vs Apexi PowerFC, whats the difference?
My cousin Peter just brought an Apexi SAFC for his R33 skyline and he had it tuned and made 204rwkw. It cost him $300 and $250 for a tune. Most people simply assume you can make power and expect 220rwkw.
They will both make very close to the same amount of power if both have been tuned correctly. But clearly the PowerFC winds hands down if it has been tuned correctly and has a bulk of its load points tuned. If you have the IGN and INJ tuned in the low load / light load areas the car will feel much better to drive, response will be better and fuel economy better than the SAFC + stock ecu. The main difference is the PowerFC will support more mods and if tuned correctly will feel like a new car to drive.
Both are only as good as the tuner.
Car 1 - rb25det with SAFC
Car 2 - rb25det with PowerFC
The truth is that car #2 isn't likely to make twice the power as the ecu costs twice as much. It all comes down to tuning and how the car drives, average power is the key here. The engine should feel nice on throttle response (IGN timing), come on boost nice (IGN timing) and cuirse will with good economy (INJ tuning). I would expect the power difference to be 5 to 10rwkw at the most in the midrange and top end.
Distinct Advantages:
Adjustable IDLE
Configurable knock warning
Configurable injector warning
Configurable airflow meter warning
Airflow meter change support
Injector change support
Complete ignition map control
Complete fuel injection map control
No speed cut
no excess airflow cut (aka boost cut)
The main problem with an SAFC and increase power levels is that its still a piggyback and when you tune more and more, it's still a comprimise. As you try and lean it out more, it (the stock ecu) advances the timing as a result, which results in more detonation. The end result is it has to be richer than is needed, to avoid detonation. With the PowerFC you can simply dial in whatever AFR's you like and IGN timing to suit, anywhere on the map. This would certainly give a good power advantage in the midrange and top end.