What (electronically) does S-AFC do?
 

If an S-AFC only changes the voltage going into the ECU from the Air flow sensor, then couldn't the same effect be done with a simple set of resistors and maybe a small circuit?

Like if I have stock 4x550cc injectors and put in 4x720cc injectors, couldn't I just change the voltage by a certain percentage and have it compensate appropriately for the bigger injectors?

The SAFC alows you to have different setting for each rmp. It take in a RPM signal and the AFM signal allong with otheres and then you can have your car tuned so its gettin the right amount of gas at every rpm, for example many NA run rich up high but lean or perfect in low rpm a resistor would step up or down the fuel at all rpms fixing some ranges while ruining others

well,,, yes,,, but... DONT EVEN BOTHER...

the S-AFC allows you to alter the voltage by RPM or boost levels depending on how you hook it up...

a resister is a static (unchangeable) device.. one you put it in.. thats it...

Most cars require fuel to be added here and taken out there..... you can't do that with a resistor..

think about it... if you could just slap a resistor on.. every cheap ass on the forum, including myself would be doing it.

double post sorry

I understand it's adjustable, I'm just wondering what it does to the airflow signal going into the ECU. If I can compensate it properly so that the car runs right with 4 720's, and still can handle enough fuel (because of the bigger injectors, pump, etc..) at 7000 RPM @ 10-12 lbs boost with a T04E, and not have to spend the dough on an S-AFC, then I'd love to do it.

The stock ecu just i won't cut it with mods, the tiny percentage it may be of now will be much more noticable with more fuel

i think what it does that can't be done manualy is send different voltages to the ecu based on rpm like minus .1 volts here and plus .3 volts there, ("here" and "there" being differnt rpms)

of course once its set it cant be really changed (in the sense that you dont wanna sit and turn a knob while driving), but a potentiometer can change voltage outputs (as opposed to the resistor idea). if you needed less or more all the way through, that could possibly ideally work. but, as we know, its never that easy.
and for what its worth, i have no idea *exactly* how one works. wish i knew how it read and changed all voltages variable-pending. neat little things, arent they. i wonder how difficult their brain really is. no smarter than a flashlight and a can of cashews i bet. some people on this forum are digging out the brains of factory ecu's, but no one has disected an s-afc??

I dunno I bet some Honda guy has taken one apart...

I'm really wondering if this can be done, either a potentiometer or resistor or some sort of cheap-o circuit...

The S-AFC basically contains an ADC and a DAC controlled via a microcontroller. The controller reads the input voltage (from the AFM) using the ADC, does it's thing, then outputs via the DAC. Not fundamentally difficult in itself. The fancyness is the display and all the various RPM points...It is very easy to build a basic circuit and program a microcontroller for static corrections, but retuning means re-programming the controller. Unless of course you put the "map" on an EEPROM. Simple for anyone with a little electronics experience. But no one wants to tweak values in an EEPROM. People want to do it on the road, in real time, with a fancy dislplay...hence why no one has made a cheap knock off...

I think the reason most people dont bother is cuz a first gen S-AFC can be had for $40-$65 :)

WHERE DO U SEE FIRST GEN S-AFC FOR 40-65 BUX.. PLEASE SHOW ME!!!

THANK YOU

why would you wanna take a chanse with the circuit you explaind not working porperlay and have an error in it and not provide anough fuel? sorry, i would rather pay the 200 dollar ebay proce and get soemthing thats proven to work.

cause if I've got the injectors and all I'm doing is going to bigger injectors to provide enough fuel, and I know for sure what I'm doing (which I don't yet), then why not pay five bucks to make a cheap circuit?

He means 1st gen knob style probably.

The 2nd gen SAFC is the pretty gui style one then you have the SAFC-II which adds a few more rpm points.

Actually Autospeed have developed and are currently long-term testing a fuel control interceptor in the form of a DIY electronic kit. It won't be nearly as flash looking as the S-AFC, but will have similar functionality. It should cost A$150-200 (US$110-150) and be available in the next six months or so. So far it looks like it gives excellent control over fuelling throughout the rev and load ranges. :)

Yes, I mean the knob style.

If you look at all, you'll find it. I don't have to name locations, trust me.

sorry to ressurect, but is this saying with 12 rpm switches and POTS i would have my own safc?!?!?