Cobb AF Learning?

[kzr750r1]

I've been watching AF Learning go up to +7 or a little higher at idle warming up and also while driving off throttle. Once I have some load on the drive train it goes away and sticks to 0. Can't understand why this would be other than crappy fuel so far.

 

Can't see any leaks so far on initial investigation. But the numbers don't make me think there is a leak.

 

Looking to the hive mind if this is normal or I do likely have an intake leak.

[Notorious]

Have you cleaned your MAF sensor recently? Do you hit target boost at WOT?

[kzr750r1]

Yeah that was the first thing I did. Also just ordered another MAF since this one is has 217K on it.

I have not punched it lately and will try tonight to see how it reacts.

Been kinda pussy footing around lately since I noticed the swings. As you know our gas sucks so I'm hoping it's just old MAF and/or winter mix causing this.

[kzr750r1]

So answer is yes. Hitting target boost of 15+ PSI. Off throttle at speed AFL numbers move around 3 to 4 range and cruise (little load) .78. No negative numbers registered. DAM is good. Very little feedback knock.

[BoozeRS05]

When was the last time you replaced the front O2 sensor?

 

I replaced my OE front O2 sensor preventatively little while ago and the new Denso unit failed within about 18 months. Everything else was fine on my data logs, but I would see big AFR swings at idle and cruise.

 

___

 

Nevermind, I think I read AFR was acting up, not AF learning. Whoops.

[kzr750r1]

That was a couple/three years ago during my rebuild. If the new MAF sensor is not a fix this would be my next step.

 

Need to open it up again and poke around to confirm all lines are solid.

 

The one that bugs me the most is the PCV dump into the intake. I don't trust that oring seal on the "sensor". Right now it's plugged with the GS AOS installed. But it could still be leaking at the intake side?

[DaveWaters]

The way I understand it if you’re watching af learning 1 you should also be watching af correction 1. Since af learning 1 is a ltft you compare af correction 1 (stft) to have an idea of what’s happening right at that moment. Like if afl1 is at +7% and afc1 is at -6% the actual fueling would be +1%. If afl1 is at +7 and afc1 is at +15 i’d say there’s a problem (adding too much fuel) I believe cobb states afl1 should be between -8 and +8. My tuner told me there can be higher swings during the winter with the winterized gas and weather changes. Watching the correction as a comparison to learning is really the best way to keep an eye out for a problem.

[kzr750r1]

Thanks! I'll flip that monitor on and take a look.

I'm really hoping this is not a leak, just winterized gas and cold temps causing this swing.

[kzr750r1]

Seeing huge swings in town and at idle. Under load both lower quite a bit. Will see how I can get a log up to show what is going on. DAM still 1 across the board.

[solidxsnake]

AF correction is going to swing a lot. AF learning is in essence a low-pass filtered version of AF correction.

 

There are 4 learning ranges (A, B, C, D), that activate at different engine loads. A is low load when idling with no accelerator input. B and C are low load with some input and cruising. D is light acceleration, roughly.

 

If you log engine load (measured in g/s) you'll see the threshold points for when AF learning switches between these four values. By default the crossover points are 5.6 g/s, 10 g/s and 40 g/s. For example, with an engine load below 5.6 g/s, your AF learning A value is active. Between 5.6 and 10, the B range is active, etc.

 

If the weather changes, your fuel changes, engine health changes, etc., and your fueling is consistently off in one of these ranges, the AF learning number will change. The ECU does this by looking at the AF correction number over time. For example, if I'm driving in the C range and my AF learning is -3% but my AF correction is hovering around +8%, then if I stay in the C range for long enough, the ECU will start bringing up the AF learning, and as a result, the AF correction will drop. This can happen, for example, if the car is learning colder weather (where it needs to add more fuel than in warmer temperature). This behavior happens continuously.

 

For all intents and purposes, if your AF learning is staying within a decent +/- range (some say 5%, some say 8%, etc), then your fueling in closed-loop is fine. As long as you're in closed loop and your AF correction isn't pegged to its limits (i think +/- 15% is the default), then your fueling is correct in steady-state. The issues with large AF learning values is that it could indicate mechanical problems assuming the tune is good. For instance, if you used to have good AF learning numbers, but suddenly the A and B range start reading high, then it's a good indication you have a vacuum leak somewhere in the intake path.

[cryo]

yeah I would compare learning to correction and see what your final numbers are...

 

Dave

[kzr750r1]

Keeping an eye on this with your input, helping alot, thanks guys. Motor seems very happy with it's new MAF senor. AF numbers look good. Car idles better, power delivery smooth. Wish I did this a few months back.