Wideband O2 behavior

[dfarney]

Hi - On my wideband O2 meter (Innovate LM2) the numbers constantly fluctuate between about 14.6 and 15.2 at cruise (2000 rpm). Is this normal? Just wondering if the narrowband O2 sensors are working correctly (95 LT1 - original as far as I know) - the O2 sensors original - the engine fresh rebuild to a 383. ported heads, mild cam, stock exhaust. Thanks Dan

[dizwiz24]

yes.

Now my question is my numbers fluctuate between 14.6 and 15.8 - with occasional spikes to 16.2 at cruise. Is that normal? Im assuming its better to be lean than rich at cruise.

However, unfortunately my car's MPG isnt anything special.

If you interested in other peoples wideband o2 operation, check youtube.

[rtracy]

Mine fluctuate also. Is it posible to get it so it doesn't?

[dfarney]

Here are some O2 mV readings from a Datamaster log. TPS% - 2.7, Speed - 36, Spark Advance - Mostly 34.0 (varied from 33.0 to 36.0), Spark retard - .2 (one record .3), Knock count did not change, 19 consecutive records from 6416 to 6434 (just so that I can find this spot again)
626 768
151 773
49 755
102 764
706 462
795 293
795 284
786 524
453 710
71 107
49 151
102 688
706 728
750 519
702 178
768 129
342 346
426 750
670 724
Is this normal? I assume that these fluctuations are what are causing the wideband O2 values to change also. Is it just that my tune is not dialed in yet?
I'm learning a lot and appreciate any and all help
Dan

[383vett]

My LM1 also fluctuates. It is normal.

[SuperL98]

In order for the Catalytic Converter to “Light Off” and continue to maintain a working temperature, it actually needs some excess fuel (rich fuel mixture) in the exhaust.
Most OEM’s will cycle from Rich to Lean (but averaging 14.7) during normal driving to provide the fuel “wash” to keep the converter happy.
See the image bellow.
That’s why the cheap AF meters, using the narrow band sensors output, bounce around and are worthless during normal cruising.
With a Wide Band AF meter, your results will depend on how the data sampling matches the OEM software’s cycle, and how much filtering (averaging) of the data is being done.
You can imagine if you read mostly on the Peaks or Valleys, how your readings could be skewed.
Most of the Wide Band meters should have settings to increase averaging or change the sample rate, which should help your problems.

[dfarney]

Thanks - I appreciate the responses
Dan

[5abivt]

It all depends on the sample rate. if the sample rate is very High then it will pick up all kinds of odd mixes especially the spikes when you are on/off throttle. take an average over a period of time at say a steady cruise and throttle position and see if it remains fairly constant.

[dfarney]

Originally Posted by 8000RPM

It all depends on the sample rate. if the sample rate is very High then it will pick up all kinds of odd mixes especially the spikes when you are on/off throttle. take an average over a period of time at say a steady cruise and throttle position and see if it remains fairly constant.

The 19 records that I posted where from a section of the log that was about 600 records long. In looking at a different part of the log that the speed was about a steady 60 and is almost 1000 records long - it looks to me like the O2mv readings jump around more that what I posted above.
My main concern at this point is are the NB O2 sensors working correctly?
The datamaster log was taken at stock settings - 9 or 10 records per second - not sure if I have that right. Would it help if I posted the log here?
Actually I would welcome someone looking at it as I am also working on reducing some spark retard and knock counts at certain conditions.
Thanks
Dan

[Rohn]

Innovate has a smoothing function in data logs so it will show less erratic. If you install a DB gauge on pillar you also can set it up to average it out. My DB shows an updated A/F about once every second. It will show like 15.0-14.9-15.0-15.1 every second a new value appears.