SAFC goes wacky when there is an electrical load
 

so the story goes...

I got my SAFC-2 wired in and set up, and was doin highway tuning. after an hour or so, I got the powerband feeling pretty good and A/F's around mid 13's through the rpm's. As the day progressed and the sun started goin down, I turned on my headlights, and all of a sudden my A/F's are in the 16 and 17's, if i floored it would go leaner than my AEM wideband could even read. I turned my lights back off, and the A/F's were right back to mid 13's. Just for experimentation purpose, I turned on my E-Fan and it did the same thing, running super lean. finally i just turned my parking lights on (a light load) and my A/F went abt .5-1:1 leaner.

Why is electrical load causing my SAFC-2 to go wacky, seemingly in direct proportion to the severity to the electrical load?

relevant mods...

-S4 SP 13B NA
-S5 alternator
-Full S4 engine and main power supply harness & relay
all swapped in an '82 rx-7
-SAFC wired in as per instructions on 1300cc.com


as said before, with basic electrical load it runs awsome, as soon as head lights or E-fan are on it can try to limp home at best

found/fixed the problem... apparently the SAFC doesnt like the TSB add-on reground of the PCM's sensor ground at the boost sensor.

drove around this morning with my scope on my VAF's input wire watching voltages, and noticed the input voltage would jump .2v whenever i turned on my fan or headlights... through a process of spacing out and thinking at work, i decided that i already have new and known good PCM grounds, so i shouldnt even need the Mazda TSB add-on ground in the first place. so i snipped the wire, and voila.... voltages barely fluctuate .01v with/with out loads and SAFC works like a champ