Narrowband issues with headers and no cats

[rhighfil82]

E38 ecu, I've almost got my MAF dialed in after installing DW injectors... I just rebuilt the whole engine.. Stroker, overbored, bigger cam 228/230 @.050. Headers, full 3" stainless exhaust.. no cats.

While my WB is showing around 1 lambda, my narrowbands are reading 700-900 mv...
So when I go back to closed loop, the ecu pulls alot of fuel causing the engine to run lean.

The closest post I found to addressing this was about changing proportional base with headers to solve misfire issues.. but I dont think that would fix my issue.

Anybody have any ideas?

[RobZL1]

In closed loop, the engine should run at stoich, not lean. Changing proportional, limit, (and integral if you have it) will only help with getting the narrowbands to oscillate properly again, and take out the jaggedness of the oscillations with headers.

It sounds like maybe you have some injector tip temp issues, or perhaps you need to calibrate your wideband?

[07GTS]

once u dial in fueling and go back to CL your wideband should be kept at lambda 1.0 if its not and the CL is functioning properly then your wideband may just have an offset u need to correct for, the narrowband settings only get them swinging properly for a changed exhaust, go for drive or idle in CL at a good like 2500rpm so its good flow and sit there for a bit watch the WB compared to the trims when they are cycling properly then look at the gap the WB is out so if its out by .2 for example u can add/subtract that to the formula at the end where its say (input/###)+ ???? add/sub the error to the ???? figure so it reads correct, if ur higher or lower u will have to add or subtract that off that figure, then drive/rev again and see if the CL operation is keeping your WB at lambda 1 if so all good if not just adjust it a little more till its right then u know its good to use

[rhighfil82]

Injector tip temp was disabled stock..
Do either of you have a log file of O2 sensors oscillating properly, that I could look at?

Before I put on the new injectors, I had a leaky injector on the same side as the WB... The AEM WB is only 2 months old... but last week when I forced a free air calibration on the WB and the Narrowbands, I noticed alot of gunk on the WB... It actually looked alot like spark plugs under rich condition.

I wonder if that could cause the WB to malfunction?

I guess until I can trust this WB, I will do some partial throttle tuning with the LTFTs..

[RobZL1]

Here's a photo from a post I made at one point:

low rpm cruise after.jpg

[rhighfil82]

Thanks! My last log doesn't look like that at all. 😅 ..gonna mess with it for a few days see if I can get it near stoich on the narrowbands and see what it does.

[RobZL1]

Do your NB's oscillate in closed loop (any amount)?

[07GTS]

what aem wb do u have ?

[rhighfil82]

what aem wb do u have ?

30-0334

[rhighfil82]

Do your NB's oscillate in closed loop (any amount)?

They are oscillating now, at least when I am on the throttle.. not so much during idle.

[07GTS]

ok that wideband shouldnt need any offset changes it just reads right, may have to do a proper free air if it was dirty before, the 02's may not cycle heaps at idle just depends on your OS but more flow usually makes more cycles

[dr.mike]

I recently posted the methodology to verify the health and accuracy of the sensor with an AEM 30-0300 or 03-0334.

https://forum.hptuners.com/showthrea...323#post621323

#9

This is preferred, over just doing a "free-air calibration". Which tells you nothing.

[rhighfil82]

Thanks guys.. I'll clean it up, recalibrate, and go through Dr. Mike's O2% post wednesday and let ya know what I find. 😊

[rhighfil82]

I got a log after a cleaning and recalibration.. seems to be a little more in sync, but I don't think it is 100% yet.

[rhighfil82]

I recently posted the methodology to verify the health and accuracy of the sensor with an AEM 30-0300 or 03-0334.

https://forum.hptuners.com/showthrea...323#post621323

#9

This is preferred, over just doing a "free-air calibration". Which tells you nothing.

Hey Mike,
I'm at about 1200msl.. my O2 reading is roughly 20.6
Seems like it is quite a bit off.. tried recalibrating a few times and it doesnt change.. but it is hot and humid out.
91? F and 28% Humidity

Would that make much of a difference? or should I be looking at getting a replacement sensor?

[dr.mike]

That's not bad at all. 1200msl should be at 20.4% +/- 2%.

Even +/- 1% is 20.2 to 20.6. So, you are pretty good.

Also, if there is any wind, it tends to read a tiny bit high.

[rhighfil82]

Well, after changing all the spark plugs and moving the WB over to the header off bank 2, the truck seems to run best off the tune using the WB vs LTFT..

...but my narrowbands are still up around 800mv.

I wonder with there being almost no backpressure, if that is fooling them?

I have some auger inserts to tone things down a bit... haven't put em in yet.