SAFC-II Zeroed Out With 550's?

[Cool Mr Steve]

I have a Safc-II with RC 550's (look at my profile for other stuff that may be important) and my tune looks quite a bit different then what I was expecting. My low throttle is zeroed out all across the board, and my high throttle I'm ADDING fuel. No bueno. What could be the issue? By the way, when I reset my ECU last, I had the SAFC at around -6% and then needed to richen it up from there. Should I have reset differently? Also, when looking at my fuel trims at idle, the number on my Pocketlogger was negative, then when I added fuel it got closer and closer to being zeroed out. Is this correct? If there was an "I feel dumb" smiley face, this is where it would go. But since there isn't one...

 

[sonicnofadz]

I have a Safc-II with RC 550's (look at my profile for other stuff that may be important) and my tune looks quite a bit different then what I was expecting. My low throttle is zeroed out all across the board, and my high throttle I'm ADDING fuel. No bueno. What could be the issue? By the way, when I reset my ECU last, I had the SAFC at around -6% and then needed to richen it up from there. Should I have reset differently? Also, when looking at my fuel trims at idle, the number on my Pocketlogger was negative, then when I added fuel it got closer and closer to being zeroed out. Is this correct? If there was an "I feel dumb" smiley face, this is where it would go. But since there isn't one...

In my experience with tuning DSMs...trying to base everything off of the ECU fuel trims is POINTLESS. Buy a wideband o2 sensor and see if you are in fact running "rich" or "lean".

 

[CanadianTSi]

You can set your Low's just fine off of your Short term fuel trim.

If your short term fuel trim is negative this means you are rich and need to take away more fuel.

 

[DiamondStarM]

You will want to base your low th setting on the fuel trims and the hi th settings on timing advance. For the lo th... if the logger reads a negative number when you add the long and short fuel trims together then you take away fuel, if it is a positive number then you add fuel. The longer you stay at the exact RPM while tuning the closer you will get. Shoot for 0 between the two, it will always change a little. Then you transfer your 4-7k setting to make a baseline for the hi th and do a few 3rd gear pulls and check your timing. Go to the "Tech Guide" for a full write up but that is the general idea.

 

[Cool Mr Steve]

Thanks for the replies, guys, but thats not quite what I'm after. I need to know why, after I installed 550cc injectors, my SAFC needs no or very little correction. Others with the same setup take out 15% fuel or so, but I'm actually adding fuel in my high throttle settings.

 

[Cool Mr Steve]

One more thing, the car had modifications before I purchased it, but it did have stock injectors. I was curious... If my car had a chip for 550's, would it have run horribly on the stock injectors? I haven't been able to do any real tuning because of some misfire/hesitating issues (new plugs and wires are on the way), but it just seems like my car would run very well if I didn't have an SAFC on my 550's. I can't think of any other reason for my car requiring so little fuel adjustments.