SAFC pros please...

agp03 said:

Thanx for the replies.

Well, I am looking at the correction factor or "corr" reading on my SAFC. It reads -30 at idle and around the teens at lo to mid throttle settings. It shows that it is "pulling" fuel, right? At WOT (I have a 50 trim) it goes to positive readings, anywhere from +4 to +25 depending upon boost settings - the higher the boost, the higher the positive number.

Since the SAFC cannot add fuel in our cars (correct?) when the correction factor goes to "zero" does that mean that the ECU essentially takes over and no fuel is being pulled at that point?

And what does it mean when it goes positive?

I do not get any codes per my scan guage. No CEL's.

For some reason, no one has been able to answer this, so appreciate the input.

Click to expand...

This is incorrect. The S-AFC CAN add fuel, however, it is not recommended that you do this as it is reduces timing advance and can throw error codes.

Adding fuel via an S-AFC will "fool" the PCM into believing you're running a higher level of boost. This in turn adds fuel and reduces timing advance. Subtracting fuel via the s-AFC has the opposite effect. Therefore the PCM leans the mixture and increases timing advance (hence the reason detonation becomes a problem when you pull a lot of fuel).

The S2 PCM is much more tolerant when it comes to adding fuel. It's ability to read up to 29 PSI (3.00 Bar) of manifold pressure leaves overhead for fuel addition via the S-AFC. This is difficult, if not nearly impossible on an S0 or S1 PCM due to their inability to read higher than 18.6 PSI (2.25 Bar). Most people running an S0 or S1 PCM are running near, if not more than, 18 PSI of boost pressure already. Therefore, even just a small addition of fuel via the AFC peaks the MAP voltage signal leading to the PCM causing the PCM to cut fuel and throw an overboost or other MAP related error code.

By the way, positive on the AFC means you are adding fuel.

If you truly need to add fuel to achieve an optimum AFR, chance are something isn't right. Additionally, your power output is likely lower than it could be due to poor timing advance.

Some feedback from you would help...

First of all, what kind of timing advance are you seeing?

Next, how much boost are you ACTUALLY running, and how much boost is the PCM seeing?

Last, at WOT, what does you injector duty cycle look like?

You should be able to attain this information from your scan gauge.

agp03 said:

Allright! Thank you!!

I was running 20 psi on the fact guage, showing 18.5 on the Aeroforce Scan Guage. The Aeroforce was also displaying an Injector Duty Cycle of 110%. (Which is my next question - why is that?)

Did you want a total advance number at WOT? I can get that tomorrow eve as I am not driving the skittle today.

BTW, AFR's at high 10's and KR at 2-4 at 20psi.

Sure appreciate your help and knowledge, I don't know how many times I have heard that you cannot add fuel and that you will get codes.

Click to expand...

Something is definitely not right with your setup...

If the AFC is adding as much fuel as it says (around 20% for example), then your scan gauge should be showing around 27 PSI of pressure when you're running approximately 20 PSI of actual boost pressure.

As far as the Aeroforce gauge showing a 110% duty cycle, I have no idea what the problem could be there. A 110% fuel injector duty cycle isn't even possible.

Yes, I would like total timing advance at WOT. Actually, if you could get the minimum, maximum, and mean of total timing advance (at WOT) throughout the RPM range, that would be even better. Be careful though, don't wreck trying to do it! :lol:

So, you're information prompts me to present more questions...

Are you running factory turbo?

Do you have S2 injectors or factory injectors? Better yet, are you running a full S2 kit or just the PCM?

Did you buy the AFC used? Who wired it in? Who tuned it?

Edit: A 100% duty cycle indicates the injector is in an active steady on state. It is impossible to exceed a steady on state; obviously. I suppose it's possible that the injector duty cycle is showing a theoretical value based on the PCM's calculated injector pulse width, but I somewhat doubt it.

Ideally, you want to keep your injector duty cycle around 80%.

OK, I'm back from a smokin' run or two. Whew!

Here's what I got: These are WOT 3rd gear from 3500 to redline. Had passenger record the following Max. readings.

Factory boost guage: 18.5 Aeroforce : 17.7 Injector Duty Cycle: 108%

SAFC Corr. Factor +15 Ignition advance drops to 24 - 25 degrees at its lowest. Starts out around 40 degrees. (I have seen it go up to 50 degrees or so while just cruising around.)

Also: Max KR 2.0 Calculated EGT 1715 - 100 (aeroforce guage correction factor = 1615 plus or minus. AFR's from mid to hi 10's.

Outside air temp: 50 degrees.

My set up: I have a 50 trim with 3' CAI, 3" TBE, AGP FMIC, Stg 2 ECU and S-2 injectors (as far as I know, that's what I was told about the injectors. Everything else I verified.). Yes, I bought the car used with all the mods already on.

I did have it tuned by a reputable shop last fall at 17 psi. Didn't seem to make much difference, I did it just to make sure everything was ok. Car has always run great. Smooth idle, no hiccups, great mileage, and no traction below 60mph:jester:

When I got my UEGO, I noticed that my AFR's were so rich (like below 10) on the guage, so I started upping the boost up to about 20 psi. That got it to the high 10's. Then I worried about KR, so got the scan guage 0-3.5 was pretty typical. Since then I have been dropping the boost down incrementally to lower the knock count. I suspect that if I put it back down to 17, perhaps my SAFC will read zero and my IDC might be at 100% or less.

Its a real puzzle.