Closed Loop Disabled but still adding fuel?

[oakley6575]

I was doing a little touch up to my MAF table and I noticed in the scanner that the 02 sensors were still adding fuel even though they were disabled in the tune. Closed loop enable was set to 284 across the entire table, and LTFT are disabled. They didn't seem to add fuel the entire time, only in occasionally. Is there a reason for this??

You can see it mostly at the very end of the log when I pulled in my driveway and let it idle for a bit. But if you skim through the entire log, you can see spikes from the 02's out of no where and then the AFR goes rich. Just wondering if this is normal?

[superwagon]

Did you clear your fuel trims before your log?

[Brad Campbell]

It looks like there may be confusion on what the oxygen sensor signals look like and mean. I believe the spike you are talking about is just the oxygen sensor reacting to the changing air fuel ratio. It isn't physically adding or subtracting fuel when that signal moves up or down. The sensors are reactive. That said it seems odd to have almost no stoich switching in the sensors at all even given the open loop operation.

[oakley6575]

When it's put in closed loop, they switch fine. But the random reactions seem seem to move my afr down to around 14.3. And when they aren't reacting, it will idle at 15. You can see at the very beginning of the log, the O2's are silent and it idles at low 15's. Then move to the very end of the log and you can see a difference.

[Brad Campbell]

I see that. I don't think i'd be concerned. When you are that close to the switch point of the sensors it doesn't take much to get them oscillating.

I should add that the fuel ratio is what causes both sensors to move. So when the mixture moves a little more rich the narrow band sensors will increase voltage and the wideband reading will show the same change. Both of the sensors are reacting to the change in fuel ratio, however they are not causing the change.

[oakley6575]

I see what your saying. So if I use the scanner to change the afr, I should see the O2's voltage increase with a richer mixture?

[oakley6575]

I have another dumb question.. I just went out and did a WOT run in an OLMAF tune. I'm commanding 12.74 with in PE and my actual AFR was around 14.4. (Thanks trusty tuner). What would be the safest way to to go about tuning the MAF for engine speeds above cruising rpm? Should I select the higher cells and multiply by 115% or so to get rid of the lean condition?

[Brad Campbell]

Yes. If you command an afr lower than stoich(rich) the narrowband voltage will increase to around 1000mV. This will also be reflected in the wideband.

First I would say don't do anymore full throttle pulls... yet. Post your tune/log up here.In short I believe the correct way to attack your problem is to disable the maf, tune the ve, and then go back to bring the maf into range with your data.

[oakley6575]

My ve is money from idle to 4000 rpm. My tune is set to switch to maf only at 2500rpm so shouldn't I just continue working on the maf?

[oakley6575]

408_tune is my normal tune and then I attatched what I'm using to tune the MAF with.

[Brad Campbell]

I would agree with you... yes.

[oakley6575]

Thanks Brad. Would you go ahead and multiply the upper airflow regions by 1.15 to protect myself from the lean condition?