longwinded safc question/theory, check it out

[jim90TSi]

i was doing a little reading and i was looking at fuel trim corrections. i have an safc2 and it has the 12 settings, on each of the settings with a stock mas and 550cc injectors, am i going to want to as 10% or -10%. In the definitve piggyback guide it says that if you have 550's a good starting point would be -10% right? They refer to both tables, that is Hi and Lo correct. With all 12 Ne points set, so i set the hi and lo at -10% all the way across the 12 points? Then with the logger and some fine tuning you ajust the percentage on each of those 12 points right? or wrong? From what im (trying) to understand, with viewing your fuel trims with a logger and noticing you need correction from being to lean or to rich, adding percentage (i.e going from -18% to -10%) you are compensating for a lean mixture, and with subtracting percentage you are trying to compensate for a part that richens the mixture(i.e injectors being larger that stock). From what i read and (tried to )understand you add/subtract a few percentage on the safc and that will take the percentage on the logger to 100%. Are you looking for your perfect fuel trims on the logger? It also says that you should adjust the fuel trim for 1k-about 3k, and then use those numbers as a standard all the way to 7k correct? Then wtih the numbers you got from the higher rpm lo trim you use right across the points on the hi trim?

going to hi throttle.....with all fuel trims at 100%
Hi-Now in the piggyback guide is says to monitor the 3000 rpm range after a 3rd gear pull (a few psi less than what you want to run?), is this just a good starting point to work your way up? Im assuming you start on the hi trim setting on the number point that 3,000 rpm rests on? Then you view the logger looking at timing and o2 voltage and use that to determine whether or not you are to rich or to lean. If you are to lean in that rpm point you add a few percentage for being lean and take a few percentage away for being rich, or is it the other way around? After that is determined, im assuming you go through the points from there on up to 7k (point 12)

Now this is what i honestly understand what i read to be true. I may be ( and probably am) wrong in most areas, that is why i posted this. is what i stated a good general idea of whats going on, or did i just type something a 3rd grader would type?

let me know what you guys think,.........thanks and let me know how dumb i am

Jim

 

[steve]

What we are doing to start with is using the low throttle settings make corrections on the SAFC to bring the closed loop operation of the ECU back into normal range.

Ideally a full stock car would run 100% fuel trims which says that the fuel the ECU calculated was required agreed with the O2 feedback. Once we mod the car we would like to tweak things back to baselines before tuning open loop (WOT). The closer you can get to 100% fuel trims at the various RPMs the closer the ECU will be to actually hitting the programmed AFR's in the maps in open loop. Injector upgrades are a good example. We get an idea of what the corrections should be from the difference in the injector sizes (450/550) - 1 = -0.18 correction to be applied across the board ignoring issues like the difference in injector deadtimes. Actual corrections will wind taking that and real flow rates into account as you use the O2 feedback to dial things in.

Once you have a good baseline you move those settings to the hi throttle and begin to do pulls to see how much you can lean the car out for performance. The factory maps are pretty rich for safety dipping as low as 9.5:1 at hight loads and RPMs so there is lots of room for improvement.

I hope that makes sense.

Steve

 

[jim90TSi]

any others