I've been having an SAFC discussion on my local board... and they came up with an interesting idea, and I was wondering if it would work and/or be benificial.

http://www.rockfordracing.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=2&t=000168#000014

is the thread, but if you don't feel like reading all that, near the bottom, the post says:

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Would it be benficial to run low FP and actually run a positive percentage
on the S-AFC to retard timing at high pressure, say 19-22psi? The idea
being that you are feeding a higher airflow to the ECU, therefore
retarding timing and still getting the right amount of fuel... At what actual percentage does S-AFC correction start causing problems with timing, or
is this really engine specific?

*****

So what do you guys think?

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I'm guessign you would use something like 440's as I am to be able to run that kind of psi.
well I have the smallest disk on my s-fmu and have the idle pressure set at 11 and it is still runing rich. YOu would have to set the idle pressure extrememly low to be able to do something like that. and at the pressure that I'm runinig I'm already messing up the conical spray pattern of the injectors wich diminishes the efficiency of the car at idle and low throttle. to set the idle pressure even lower would increase this problem. not sure what the effects of it would be, but at such low pressure the car will not idle right if at all.

-97 GS (First project, 299 whp)(sold)
- 97 RS 2.6 last numbers: 306hp, 352tq @16psi (Dead, parted out)
- 99 GS OZ, Hahn Kit, 56k miles (Sold)
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- 00 Nissan Maxima GLE (Daily Driver)
- 02 Audi A4 1.8T Quattro

I've always wondered that, but figured purposely running too low a fuel pressure might not be safe, and figured thats why no one did it. I don't like all of this electronic trickery anyway... control ignition with an ignition controller, control your injectors with another controller.

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SO the smaller the disk and ring the RICHER you will run? I am running the S-AFC with 415's and wanna know also.

Jonathan
95 Eclipse GS
8 injector
Hahn Stage 3.5
Howell 2.2L Stroker

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richening up with the sAFC increases MAP voltage. This means that you might actually put your MAP voltage to the point where fuel cut occurs.
-=B-=

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it's the other way around. the disks with larger diamaters make it easier for the diaphram S-FMU (or any other regulator for that matter) to exert more force "restricting" the return line, which increaces fuel pressure.

The1Bill is right. the AFC changes the voltage a substantial amount. i've been having problems with my missing link with fuel cut right around 0 psi - the best solution for me is to mess with the AFC so that at static it will lower the MAP voltage getting me out of the fuel cut range. uncorrected MAP voltage is about 4.7 volts at static, but corrected is probably slightly below 4.67, the level at which most people experence fuel cut.

2016 WRX STi Limited (current)
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One thing to consider is the actual pulse width of the injectors at wide open throttle. Are they at 100%? Maybe 95% or 90%? For the S-AFC to trick the ECU into providing more fuel, there must be room to increase the injector pulse width. If they are already at 100%, there is no room to open them further. If they are at 90%, then that isn't much to play with. And you run the risk of a CEL (MAP output too high) if you richen with the S-AFC when under boost.

Corbin

'95 ESI-T
HRC+FMIC+ETC...



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