Setting Low Throttle on SAFC II

[SteveR6]

Ok, this is starting to get under my skin, from what I've read you set the ne points up then free rev the car to those rpms and hold it and adjust the STFT until it's 0 +-2 correct? For some reason when I get the car to the rpm it's marginally off for a second then it fixes itself and goes pretty much exactly where it's supposed to, there's no way my computer is this good is there? Also my LTFT seems to fluctuate, sometimes it's 4 sometimes 7 etc. Should I even be paying any attention to it? In the tech section it said to take the average of the STFT and LTFT and get it to zero but another article said just focus on the STFT.

 

[MyBeatGSX]

The tech article isn't accurate. I tried to tune like that and it makes no sense. STFT changes with throttle position, load, etc. It can be completely ignored.

Just try to 0 out the LTFT. I wouldn't do it free reving higher than 2k, you don't drive with no load on the engine. Do the rest of the points while light throttle cruising down the highway.

 

[spyderturbo007]

You are looking for the sum of LTFT and STFT to add up to as close to zero as you can at each Ne Point. For example, if you have a 1k Ne point and your STFT is +5 and your LTFT is +5, you need to add fuel at 1k.

On the other hand, if your LTFT is -5 and your STFT is +5 you are fine. STFT tells you what the ECU is doing "this instant". The LTFT is more of a, well, long term correction. As the ECU sees a consistent STFT value it will begin to transfer the STFT value to the LTFT in an attempt to zero out the STFT.

So, if your values are -5 and +5, within a couple of minutes, both will be zero.

 

[MyBeatGSX]

Nate, I know that's what the FAQ says, but it makes no sense at all. I can change my STFT to whatever I want just by holding the throttle at different positions. If I have them zero'd the way you discribed at say 3k on flat ground at 15% throttle. They will no longer be zero'd (STFT will go more +) if I go to 20% throttle. If I get off the gas to say 10% throttle, the STFT will go more negative. So who's to say what throttle position it should be zero'd for?


I've found it much better to let the STFT do whatever it wants, it is impossible to tune for, and just keep the LTFT as close to 0 as possible. This is how my car is tuned and LTFT's have stayed within +/- 1% for the past 2 months regardless of throttle position or conditions.

Can you explain more?

 

[SteveR6]

I know what you mean about the load. Just out of curiosity after setting the STFT while in park I clicked into drive and guess what? The numbers were off. So I reset the STFT to 0 revving to 1K in drive and I'm going to do the others on the highway tomorrow or over the weekend. I wish someone could clear this up so I know I'm doing this right.