Hello All,

Let me start this off by saying I am wearing my flame-proof undies... I am sure I will need them.


I have searched but not found a "process" to make\adjust my narrow-band O2s agree with the numbers I am seeing from my wide-band. My wide-band is just a few inches behind the Narrow-band.

I can tune my VE table with a wide-band, but as soon as I go back to closed-loop my fuel trim numbers are wrong by approximately 4% (compared to the open-loop wide-band #s).


--Is there a process or method to adjust\calibrate for this?
--OR... is this just the way it is and I should learn to live with it???


Let the flaming begin...

...any help appreciated!


2002 C5 ZO6
LG LTs
VaraCrap
224/228 114+4

 

"-Is there a process or method to adjust\calibrate for this?
--OR... is this just the way it is and I should learn to live with it???
.
You can change the O2 switching voltage by a few thousandths, see if that helps tame the OCD

 

If you plan to run in closed loop normally, then tune the closed loop areas with your narrowband fuel trims. The wideband is really only needed for your open loop power enrich areas. Unless they are just defective, the narrowbands are always more accurate at stoich than the wideband. As for making them match, that would depend on whether you are taking a direct serial out signal from the wideband or interpreting an analog out signal.

 

Thank You... for the reply.

So I posted on 3 different forums...
... and I am getting the "...this just the way it is and I should learn to live with it" message from several posters.

Which is all good... I was just wondering if I was missing something and\or needed more research. Given how small this cam is, I really don't feel good screwing with the Narrow-band O2 switching voltages.

Again... thanks for the comments.

 

Are you tuning in Lambda or AFR?

 

Im having the same issue with my AEM wideband. I am tuning in Lambda. When I have my STFT dialed in to 1-3% my wideband reads 20-30% lean. Super annoying. I installed a new sensor and did the free air calibration.

 

Working off the title of this thread, I have a question on the function process of a narrow band O2 sensor.
Aren't they basically a 3-position response sensor? As in Lean-Stoich-Rich, with no variations between the 3?
This is as opposed to a wide band that actually reads a sliding scale of AFR measurement.
Please educate me on this.

 

Have you verified there are no exhaust leaks near the WB sensor?

Do you have a gauge or just logging it in HPTuners?

 

The narrowband voltage response is shaped like an extremely narrow parabolic curve, with stoich right in the middle. There are variations in voltage, so it is not a 3 way on/off, but outside of stoich the curve is so steep as to be almost useless.
edit-- A parabola was the wrong shape to reference, because obviously the voltage swings in 2 directions, and not the same way for both rich and lean, but the basic idea is the same. I have issues picturing things in my head.

 

Thank you VERY much! I'd always wondered about it, and you clarified it nicely!

 

I had to make an edit to my post to clarify things a little better.

 

I think I kinda saw that, and got the general idea. Basically, too narrow a defined range to be useful for tuning.

 

I have a AEM wideband gauge in the car. I removed the sensor, wrapped it in a rag soaked with brake cleaner, turn the key to on and it reads full rich. .55 Lambda

I checked the for exhaust leaks to the best of my ability but Im still not a 100% sold that there isnt any. I mean, if there is I cant notice it. I got the collectors clamped with U bolt clamps and I also wrapped high heat tape around them. The Y pipe is old and the ends that slip over the header collector have been beat up a little from prying it off and on.

That Y pipe is looking like the culprit

I did a test today. I put the WB sensor into the header collector bung, and the Driver O2 sensor in the bung thats in my Y pipe. I started the car and The wideband reads right at Lambda, My STFTs read -25 +/- 3
With the WB in the bung thats in the Y pipe and the driver O2 in the header collector, the WB reads about 15% lean and the STFTs still read -25 +/-

 

When operating in closed-loop mode, your fuel trims can fluctuate within ±25%, yet the wideband oxygen sensor should still read 14.7 AFR. Additionally, the further downstream the wideband sensor is placed in the exhaust system, the less accurate its readings will be at idle or low throttle. In most cases, I find that factory narrowband O2 sensors provide more reliable data than a wideband sensor under these conditions and only use the WB for WOT.

 

The WB sensor is about 5" down stream from the O2 sensor.
I'm going to pull the Y pipe off and pressure test it to look for leaks.
if it checks out fine, then I dont know what to do.

I tuned my VE table to where the STFT were within 3% but then the WB read 15%-20% lean.
Your saying just ignore the WB at idle then?

 

If your fuel trims are +-3% at idle and part throttle I would ignore the wideband. Put it in OL and see what the wideband says...either way I trust the O2's more at idle over the wideband.

 

Okay, I will give that a try. Thanks for the tips.