At part throttle?

 

yes. the SAFC2 has a low load setting and a high load setting. it is throttle position based so may not be as useful as something that is dirived from loads (airflow). basically you set your low load values, for each of the 8 rpm points, then you set the high load rpm points. the transition from the two should be somewhere higher in the throttle position so your not running rich all the time that your not actually flooring it. when you are giving it some gas, then once you pass the transition you will move into the high load values which can give more fuel to compensate for the more air your getting. so yes, at partial throttle you should be in the low setting which can be tuned to run however you want.

hope that helps.

 

I was actually wondering if the ECU overrides it in closed loop.

 

well because the afc is actually run in series with the airflow meter signal, the ecu cannot override it. the only function the AFC has is to massage the airflow signal, and the ECU cannot ignore the airflow signal thus the afc cannot be ignored.

 

Ok, thanks.

So would it make sense to use one map to set at LO - 35% and configure all the low RPMs to run a little lean for better mileage and have it go to 0% correction above 35% throttle and above, say, 3500 RPMs? That way when you are driving softly or cruising or idling, you can use less gas? Then just let my TT flash do the work at other times? Then use the 2nd map for race gas? How's that sound? Bad?

 

although i haven't had my AFC hook up in my evo yet (considering doing it for dyno day...), i don't know what correction percentages are good or not for this vehicle. however, your TT flash is going to be working at all RPM's and all airflow values. the AFC will only be modifying your TT flash by adjusting the Airflow signal. so if mark did an excellent job (which i'm sure he did), your AFC isn't going to give you any performance gains at all on full throttle. but you are correct in thinking by using the AFC for low throttle to reduce the amount of fuel being used by changing the airflow correction to -35% (or whatever is a safe value). and just make sure that you keep the high throttle position values at zero so the TT tune is doing the job it was tuned to do.

one other thing to consider is how the ECU takes into account A/F ratio given from the 02 sensor. if the 02 sensor is giving readings that are to lean it will increase the fuel flow regardless of what your AFC and TT tune are telling it to do. i don't know enough about how that function of the ECU works with that so i wouldn't worry to much about it (or just ask mark he prolly knows). i do know that the narrowband 02 sensors are actually switching sensors. what this means is when a narrow band 02 gauge is hooked up it will bounce back and forth at idle. then when the car is accelerating it switches to a constant reading which the car can correct for. at idle (and zero acceleration) i don't remember why the sensor bounces back and forth, but i remember it had something to do with the ECU averaging the readings (the guy at bosch told me how the sensor worked, but it has been more then 6 months sense then, and thats knowledge that rarely gets used unless your an engineer for bosch, so of course i forgot exactly what he said).

 

Yeah that's cool then. I was just wondering if by taking out some fuel at low RPM and low throttle input it would have an effect or if the ECU would override it. It sounds like it will work. Yes, I will keep the settings to 0% for over 35% throttle and over 3500 RPM considering when I am driving hard I am not really ever below 3500 RPMs. Now my only concern is how much fuel can I take out safely. I can make the SAFC full lean or rich at idle and nothing really happens. That's what prompted my initial question.

 

well nothing would happen at idle since the ecu is still in closed loop. Only after 30% throttle will the ecu submit to the afc.

 

Sit in the car with it idling and change the 1000 RPM setting for low throttle point and then say that....

 

i have and nothing changed on my wb, thanks for making yourself look stupid.

 

Congratulations. You have a wideband.

I've tuned 5 DSM's and 3 Evo's with S-AFC's and if you can sit in the car with it idling and adjust the low throttle point for 1000RPM um and down and NOT notice a change in the idle RPM, then you are doing something wrong.

Hey, while you're talking about people looking stupid, why don't you go to this page and PLEASE tell us all why you would even set the low throttle portion of the S-AFC if it did nothing at all during closed-loop operation (part throttle).

Notice how they changed to larger injectors and tweaked the MAS, then they had to add a marginal percentage to the AFC? Guess why they did that, and guess why they did it around the 1000 RPM point. Are you still in denial that the S-AFC manipulates the signal under closed-loop operation?

 

I can see how the signal would be changed under closed-loop, but wouldn't the ECU eventually relearn with the corrections and cancel them out? So if you were to sit in a car with a wideband and change the AFC settings for 1000 RPM, it would change the A/F ratios, but wouldn't it eventually learn its way back to 14.7? Just curious as I have never played with this.

-Paul

 

The car doesn't really run overly rich until it is at WOT. They actually run pretty damn stoich as they just sit there and idle. Well, they are a lot closer to it than when boosting, but anyway. The AFC simply intercepts the signal that is comming from the MAS, going to the ECU. It is nothing more than a delay line that either increases or decreases frequency count, making the ECU think it is flowing more or less air. It doesn't add more or less fuel, but it does add more or less "air" to the mix. The ECU then sorts out and determines how much fuel needs to be sprayed in to mix with the air that it has been told is there. It won't "hunt" for stoich because the ECU is in closed-loop operation. When you go hard on the gas, that is when it turnes open-loop and that is when it really tries to become Stoich. The air flow values matter most here, otherwise you can hit fuel cut/run too lean/run too rich. Yes, you can do all these things while barely accellerating or idling, but they are a lot less harmful at 550 degrees than they are at 800 degrees. I've never heard of the ECU relearning and canceling out the S-AFC, and I don't think it will. It will simply try to find Stoich and hold it there, which it does by adjusting fuel - not air.

 

Well guys thanks for all your input. I got my answer from Mark at TurboTrix. The Evo ECU learns so quickly that, even though the AFC will do something in closed loop, the ECU will compensate fairly quickly and negate the settings. The SAFC will only be effective in open loop. Therefore, LO throttle settings on the AFC are pointless and can be left at 0% correction and HI throttle settings are only effective when the ECU is in open loop. Take care.

 

mmmmmmmmk....But I've still seen idle changes when screwing with the settings...Maybe I didn't let the thing sit still long enough for it to "sort" itself out...Bah, I'm tired. I've been at work for over 24 hours now, and I need some sleep. Sorry if my info was misleading in any way or whatever. Maybe I'll be more coherent later on.