SAFC2 Tuning with 680s

[turbospyder19]

I am trying to tune my SAFC2 but am having some trouble. My fuel trims between 3k and 4k are STFT: -17% and LTFT: -2%. I tried adjusting the correction just about everywhere on the SAFC but am not seeing much change. What corrections are usually used in this range for 680s? I'll get all my current corrections up here if I need to. Thanks!

 

[CanadianTSi]

Judging by your STFT of -17 you are waaaay rich in that area. Go cruise around at 3-4k and take out a bunch of fuel and your STFT should drop almost immediatly.

 

[turbospyder19]

SAFC settings below 0% are lean, right? So negative Fuel Trims are rich? Thanks!

 

[RageGST2G]

oh I misread what you were saying...

I was under the impression though that settings above 0 on the SAFC make it more lean, not less... but I'm probably wrong

 

[spyderturbo007]

Settings above 0 on the SAFC-II tell the ECU that there is more air entering the engine than there really is, therefor the ECU injects more fuel than is needed. Because the ECU doesn't know that you installed larger injectors, it opens them for the same amount of time that it would the stock 450's. This results in a rich condition because the 680's will flow more fuel in the same amount of time as the 450's.

Anything below 0 on the SAFC-II tells the ECU that there is less air entering the engine than there really is and the ECU injects less fuel than it normally would. This is how you compensate for the larger injectors and the increased flow.

A STFT or LTFT that is negative tells you that the ECU has received feedback from the O2 sensor "saying" that there is too much unburnt gas in the mixture (consistent voltage above 0.50V, where 0.5V is the Stoichometric point of 14.7:1). The ECU then adjusts the fuel map by removing fuel. Thus, your FT's are telling you that the ECU is removing 17% of the fuel it would normally inject. Keep in mind that 1% on the SAFC-II is not the same as the 1% you are seeing from the ECU. 1% on the SAFC-II is about 2 - 3% as read from the ECU.

Just remember that if you have a negative FT you need to adjust the SAFC-II more negative and if the FT is positive do the opposite....adjust the SAFC-II closer to 0.