AEM F/IC writeup

I purchased it used. It was already wired up by another user, but some things were wrong, some solders were bad, his resistance was too high, he had no resistance on the O2, etc and so forth, so I completey redid it.

I wouldn't cut into the main harness, that just seems like a nightmare, especially since you'd have to do all your work in the passenger footwell.
 
Sorry for the late reply. I did used the O2 modification for a while, and I put two potentiometers in series and tried damn near every resistance from 1k to 20k. My OBDII was responding to the FIC modifications at idle, but my results on pulls were inconsistent. My theory was that the 5ms read, 195ms pulse was enough for the PCM to sometimes catch the actual O2 sensor signal instead of the modified version, but I am not really sure. Sometimes I had nice low AFR's in closed loop and silky smooth transitions to open loop one run, and then back to 16:1 and an abrupt transition stock behavior on the next run. I only had the crappy Harbor Freight scan tool at the time, so it was hard to say since the resolution was so low. To know for sure, I would need an oscilliscope on the output of the FIC and somehow sync that with the FIC's data logger.

Instead, I put my O2 sensor on the Analog A IN/OUT. This made much more consistent results, at the cost of some functionality. AEM recommends using the Offset and that's what I found worked the best anyway, and you still have that feature on the Analag signal modifier, so fair trade in my opinion.

The only time I ever got a CEL is when I purposely zero'd out the O2 sensor voltage, it only took a minute maybe for the CEL to trip. I did get a CEL for my MAF signal was too low before I had that resistance and map table setup properly, but since then I haven't had any CELs in a several weeks (has it been months now?) of tuning and driving.
 
My MAF isn't clamped. I am running stock (ATP wastegate) boost on the turbo that came from the factory.

It's not the MAF that causes the fuel cut directly, it is the duty cycle of the injectors. They cut out once they hit 100% duty cycle. The biggest variable in that equation is the long term fuel trim.

With my setup, in January in Phoenix, and LTFT's 0'd out, I was hitting cut right at 4.8v. But before I had my scan tool and understood the fuel trims completely, my LTFT's had crept to 25% and I would hit cut as low as 4.6v.
 
Thanks for the info just making sure.. My primary 02 took a s*** and know we have to figure out the 02 table offset again unless you could please send me yours..
Thanks
 
My table is very simple. All cells below 15 PSIA are 0, at 15 and above, all cells are at -0.402. This brought my closed loop AFR to right around 12.0, and I added 14% fuel in the closed loop region to zero out my trims.
 
I did what a huge difference since it has the atmosphere calculator!! And since the FIC modifies all the injectors individually instead of the signal as a whole
 
big Lou said:
I did what a huge difference since it has the atmosphere calculator!! And since the FIC modifies all the injectors individually instead of the signal as a whole
Click to expand...

So you think its definitely worth the switch? From what I've been reading it seems like its definitely worth the switch. Not to mention I can sell my AFC for funds towards it.
 
Running strong still passed state smog!!! And no check engine lights!!! Handling the 600cc injectors like a champ!!
 
it's akward to explain... Sometimes it will stumble... but usually it's fine and runs a little rich then it will correct itself and lean out. Besides that no idle issues!!
 
It's because any time you are under boost you are altering your O2 reading with the AEM (depending on how exactly your tuner tuned your O2 map). Unless you get it absolutely perfect, STFT's at 0 across the board, you'll pass that extra fuel onto your LTFT's which will get added at all times, including idle. So you will now run rich, until the PCM can correct itself again, while the AEM isn't modifying the O2 signal.

You could try to get your offsets more exact, but I think it's a lost cause, because it will change with all sorts of variables. Unless you decide to go full standalone, the little stumbles will probably always be there.
 
So its better to go EMS 4 than F/IC then , how offten does MAF signal get out of wack ? MSP ECU is notorious for being stubborn to alternation of input signals ... thats my main reason to moving away from F/IC at this point.

Big Lou , would you mind sending me your current map set ups, you have its manual as well bc i can't seem to find it at aem site.
 
At 27 pages now, it's a long read, but I've tried to explain as best I can in prose and some screenshots the limitations of the FIC, which is true for any piggyback. The stumbles have nothing to do with the MAF signal "getting out of whack". The AEM is definitely the best piggyback once you get the MAF signal at an appropriate voltage level and the O2 modification working, but it's still a piggyback and at the mercy of the PCM. Mine was perfectly stable, with no hiccups or stumbles, but it took many weeks of data logging and experimenting to get the fuel and O2 offset perfect in closed loop. What I couldn't control was when exactly the PCM would switch between closed and open loop, since there are scenarios that the AEM could not account for.

The EMS4 does not have those limitations, but is priced accordingly. I am leaning towards the Megasquirt now, because it is a lot cheaper, has limitless expandability, and open-source software. I haven't ever used one, and not really sure if I have the time needed to get it running right, but it's not a terribly expensive experiment, and I figure I'll learn even more than I did with the FIC. I just need to stop looking at these expenses as blowing money on an old car, and more just as the education and entertainment of a hobby.
 
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