Narrow and Broad band O2 sensors and open vs close Options

[lmcchesney]

Sorry guys, but I've been doing some reading again. Dave, you and I have had some of this discussion before and I would respect your continued thoughts on this setup. The crux of the matter requires understanding of the circuit utilized to turn the lamba analog data into useful information. Well, here goes.
O2 sensors in a distal position provides indirect input for the estimation of the A/F ratio seen by the engine. This information is useful in defining a lean or rich mixture seen by the sensor for the most recent peroid of time. Broad band O2 sensors are capable of producing a wide range of output voltages which can be inturpeted for measuring the ratio. In fact, the output from broad band sensors can be feed into the Electronic Control Unit several times a second. This allows for real time adjustment of the A/F mixture. Thus output from the O2 sensor is recieved as input by the ECU which inturn alters injector time/volume to preprogramed mixture. This feedback/adjustment defines a closed loop system.
Narrow band O2 sensors also read A/F ratios. However, A/F mixtures ranging from 13.7:1 to 14.4:1 results in a change in voltage output from lowest to highest (0.1v to 1.0v).
If you use a analog voltmeter or equalivernt A/F gague, the response rates are such that your readings bounce requiring seat of the pants estimate as to where the mean is.
However, with the use of circuitry involving a IC unit, the voltage output can be lengthed to a series of LED's.
My question, can not a narrow band O2 sensor be utilized to monitor A/F ratios throughout the power band. Noting the results, provide information for enrichment/leaning in the adjustable ranges of D-jet. ie, idle, partial throttle and WOT.
Cannot in dash monitoring with such an A/F circuit be helpful to identify serious alterations in the engine and prevent damage from excessively lean running?
Cannot the useful information from such an A/F monitor be inproved by silmiltaneous monitoring of CHT/oil temp?
I still do not understand the advantages of a broad band O2 sensor when used in a open loop system.
I cannot also see the significant advantage of a heated O2 sensor for monitoring the A/F ratios during that first 3 minutes.
Thanks,
L. McChesney

[TimT]

One way to recognize the limitations of the narrow band is to look at the graph....

The graph shows that the narrow band is basically designed to read one a/f setting... hence the very step curve at 14.7

narrow band is a yes/no type system

wide band tells the degree of richness of leanness....not "its rich, or its lean"

Some modern vehicles use a combination of wb and nb sensors....

wb before the cat, nb after the cat as a check.

My Mountaineer had 4 02 sensors.. a wb before each cat, and a narrow band after each cat...

Some, not all of the aftermarket WB gauges have a simulated narrow band output, so that the wb output is conditioned to be used as a narrow band sensor... in order to control the ECU...

I have an FJO wide band sensor... it uses NTK LH1 sensor... the sensor costs about $180... and lasts about 20000 miles in leaded fuel

I just finished a build and calibrated a Tech Edge wide band to replace the beat to crap FJO... and Im quite happy with the results...the Tech Edge uses a 7057 Bosch sensor (about $30) and the accuracy is equal to that of the FJO unit..

The megasquirt people are working on a "wide band controller" which is even more accurate than a wide band a/f gauge...