Disabling "AF #3 correction"

[Tor]

Does anyone have experience with disabling the fuel correction from the rear o2 sensor?

4-500 samples correction on stock header:



http://datazap.me/u/tor/tor-119?log=...zoom=4191-4739

4-500 samples on Gruppe-S header catless:



http://datazap.me/u/tor/tor-222-400k...zoom=7307-7716


Looks pretty erratic on the catless header. I tried to zero it out and before my ECU set -3 LTFT. After (with not so much learning) +1.2. Anyone know if there are any disadvantages? I don't know if this could be responsible for months of headache with unstabile LTFT?

The rear sensor is pretty close to the collector. Could it be influenced by the other runners in some kind of reversion?

[Tor]

Another bit of log:



http://datazap.me/u/tor/tor-201-auto...mark=1292-1289

Just at a transition between CL and OL, with MAF V around 2.9 and MAF 60 g/s, AF #3 correction throws in 1.82% extra fuel and STFT corrects against it with -1.78.

That can't be good?

[steve99]

A few guys on here have disavled rear 02 compensations due damaged 02 sensor , seems no noticable effects

Anyone with a rear 02 connected flex kit will also have those compensations disabled

You will also need to disable a couple of cel codes as well as the three compensation tables set to zero

Aparantly tjese conpensations only used during cruise fueling like on highway

[guybo]

Your fuel trims are fine. LTFT Within +/- 5 is ideal, within +/- 10 is acceptable, don't worry about STFT. Your total trim is great. But you need to tell us what your trims are at idle and at 2500 RPM

[Tor]

Originally Posted by steve99

A few guys on here have disavled rear 02 compensations due damaged 02 sensor , seems no noticable effects

Anyone with a rear 02 connected flex kit will also have those compensations disabled

You will also need to disable a couple of cel codes as well as the three compensation tables set to zero

Aparantly tjese conpensations only used during cruise fueling like on highway

Thanks Steve. Setting the "A/F #3 correction Limits" to 0 doesn't trigger any CELs, so I think it's safe to say that it's only necessary to do changes to other tables if removing the sensor completely.

"AF#3 learn" is also still active in my logs. I'm not sure what table that corresponds to in RomRaider, if any. These are small corrections between 0 and +0.34 and only during OL. I am wondering if it's "A/F #3 CL Target Compensation Limits", the description in RomRaider seems like gibberish to me, but the limits of that table are +0.5/-0.5.



http://datazap.me/u/tor/tor-228-4-6?...zoom=9089-9437

Originally Posted by guybo

Your fuel trims are fine. LTFT Within +/- 5 is ideal, within +/- 10 is acceptable, don't worry about STFT. Your total trim is great. But you need to tell us what your trims are at idle and at 2500 RPM

Thanks for your reply! All help is always appreciated, so I don't hope it comes across wrong when I say it seems either you missed the point or I didn't express myself clearly in the original post.

I am not worried about either my LTFT or STFT at all. What is bothering me is when my ECU one day set WOT LTFT of e.g. -1.2 and the next day e.g. +3.56. That causes a wildly unpredictable AFR that one day is too lean and the next day too rich. The point of this thread is to see if the swings are caused by the rear o2 sensor compensation being erratic for one reason or another (like header design, lack of cat or combination or a 4th unknown reason) and what the effect is when disabling those compensations.

[Tor]

Also, does anyone know if A/F #3 correction is possible to log with OFT and what it might be called?

[steve99]

Originally Posted by Tor

Also, does anyone know if A/F #3 correction is possible to log with OFT and what it might be called?

It would be possible for oft guys to add that parameter to oft logging, but if its not in the list you have to get them to add it.