The purpose of an s-afc is to tune the stock fuel curve up or down where it is needed. I have heard ,however, that it is impossible to tune a TII's fuel curve UP with an s-afc. Is that statement true? If so, why?

 

Untrue. The S-AFC can adjust the amount of fuel injected by ±50% by lying to the ECU about the amount of air entering the engine. Obviouslt it'll only acheive this if the hardware can keep up, but you definitely can still make the mixture richer if you need to.

 

you can't go much richer as the stock injectors will be maxing out.

 

You would be better off having too much fuel at flatline and then tune the safc down to an a/f ratio of 11.5:1 or whatever you want.

My 87 tII with a Walbro fuel pump, RB full exhaust, FCD, and slightly upgraded compressor was running dirty rich and had to be tuned down by up to 10% on the safc. No intake mods and only 6psi of boost. I'm staying safe till I get a new motor.