O2 sensors...

mrvette

mrvette

Phantom of the Opera
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I know there is a thing about wide band O2 sensors and the more common narrow band that fit in a typical car.....they want some 200+ bux for a wide band sensor...so the question is....

Is the difference in the programming of the computer?? or something in the sensor itself?? and if so WHAT??

I hear that it senses a balance between outside air and gasses.....

so why can't it sense outside the 'range'??? if it was simply a chemical type thing, why cant the program take up the slack in the output???

:shocking:
 
The narrow-band O2 sensor is just basically a switch....it is sensitive only at about 14.7 a/f ratio...it can't discerne between 15.5 and 17.0, or 9.0 and 11.5. The wide-band can. It is linear from roughly 18.0 down to 9.0. The ECM's that are using a narrow-band only look for the transition, and which side of 14.7 the mixture is. The wide-band has more "band-width". Most aftermarket ecm's are set up for wide-band. I don't think it is a software issue only. Also, wide-band sensors have internal heating elements to allow closed loop operation at low load and rpm's, where engine exhaust heat is insuficient to insure correct operation.
 
Big G......So I have heard.....but when hanging my DVM across the O2 output, I see a linear range of operation, it's not going like on off, or anything, but actually a smooth transition I don't recall hanging a scope on it though....

it don't 'seem' to act like a switch, as in go-no go.....

so I was wondering about the programming keeping up with it and how fast...etc...

I have heard it described as a switch many times....but my DVM said different and so that's kind of interesting in that the computer never really knows wether to go lean/rich by any amount....just to go one direction or the other untill the 'switch' says something different....

that would sort of explain this hunting 'conversation' always going on at steady speed or idle....

but that whole theory seems lacking....

:stirpot:
 
mrvette said:
Big G......So I have heard.....but when hanging my DVM across the O2 output, I see a linear range of operation, it's not going like on off, or anything, but actually a smooth transition I don't recall hanging a scope on it though....

it don't 'seem' to act like a switch, as in go-no go.....

so I was wondering about the programming keeping up with it and how fast...etc...

I have heard it described as a switch many times....but my DVM said different and so that's kind of interesting in that the computer never really knows wether to go lean/rich by any amount....just to go one direction or the other untill the 'switch' says something different....

that would sort of explain this hunting 'conversation' always going on at steady speed or idle....

but that whole theory seems lacking....

:stirpot:
Click to expand...

It is referred to a switch because the old ecm's only look for the transition through about 450 millivolts, which represents 14.7:1 a/f ratio. The older ecm's can't interpolate anything other than this transition. Wide-band sensors send the ecm useful data on a much more accurate level. Getting a "tune" on an older ecm/engine combo is much tougher than an ecm that uses a wide-band sensor that allows a greater control over the a/f ratio.
 
big_G said:
mrvette said:
Big G......So I have heard.....but when hanging my DVM across the O2 output, I see a linear range of operation, it's not going like on off, or anything, but actually a smooth transition I don't recall hanging a scope on it though....

it don't 'seem' to act like a switch, as in go-no go.....

so I was wondering about the programming keeping up with it and how fast...etc...

I have heard it described as a switch many times....but my DVM said different and so that's kind of interesting in that the computer never really knows wether to go lean/rich by any amount....just to go one direction or the other untill the 'switch' says something different....

that would sort of explain this hunting 'conversation' always going on at steady speed or idle....

but that whole theory seems lacking....

:stirpot:
Click to expand...

It is referred to a switch because the old ecm's only look for the transition through about 450 millivolts, which represents 14.7:1 a/f ratio. The older ecm's can't interpolate anything other than this transition. Wide-band sensors send the ecm useful data on a much more accurate level. Getting a "tune" on an older ecm/engine combo is much tougher than an ecm that uses a wide-band sensor that allows a greater control over the a/f ratio.
Click to expand...

I have hated the idea of spending 200 bux for a wide band sensor, when they apparently do not last to well....shorter life span, so to not leave it in the car very long....
 
Ín an ideal world, the narow band is also all you need. The wide band however is much better used for tuning as the sensor voltage is linearly related to the AF mixture and as such you can draw conclusions based on the signal

The way these sensors work is simple, it's a zirconia element that is eprmeable for O2 when ehated up )reason these things must be warmed up). As with everything in nature, there's always a desire to attain an equillibrium. Now, this also happens when it comes to concentrations (think about osmosis like in plants), the exhaust gas is low on O2, outside air ahs a somewhat fixed amount. When the O2 sensor is heated up, O2 from outside wants to permeate through the zirconia element to dillute the exhaust gas, in other word to raise the O2 conc. to the level of outside air. Now, this will never happen but the driving force for this to happen depends on the concentration difference 9chemical potential). See how the O2 content in the exhaust gas is affecting this? As O2 passes through the zirconia element a charge is created, this charge is related to the conc. difference.

This is the voltage output (yes these things generate voltage) for a narrow band sensor

NarrowbandOutputGraph.jpg


See, it's only linear around lambda =1 and drops off logharithmic very fast on both sides. Now you CAN!! change this signal by chopping up the x axis and resclaing it. I've seen it done by a buddy of mine, he used it to create a linear bar graph type AF meter. Now, with scaling you also increase the measuring rror and such.

The wide band signal is much more useful:

WidebandOutputGraph.jpg
 
mrvette said:
I know there is a thing about wide band O2 sensors and the more common narrow band that fit in a typical car.....they want some 200+ bux for a wide band sensor...so the question is....

I hear that it senses a balance between outside air and gasses.....
Click to expand...

Most of the cost of your FIRST WB sensor is in the controller/power box. I bought a replacement WB sensor last year for about $40.

A big advantage of WB sensors is that you can use one to tune your system to something other than 14.7:1 A/F. Max power is at around 12.6:1 and max economy is around 15.4:1. If you run a supercharger or turbo, they are a must...

The back end of a WB sensor is open to the air. It senses the difference between the exhaust oxygen content and the oxygen content of air.
 
Z-man said:
mrvette said:
I know there is a thing about wide band O2 sensors and the more common narrow band that fit in a typical car.....they want some 200+ bux for a wide band sensor...so the question is....

I hear that it senses a balance between outside air and gasses.....
Click to expand...

Most of the cost of your FIRST WB sensor is in the controller/power box. I bought a replacement WB sensor last year for about $40.

A big advantage of WB sensors is that you can use one to tune your system to something other than 14.7:1 A/F. Max power is at around 12.6:1 and max economy is around 15.4:1. If you run a supercharger or turbo, they are a must...

The back end of a WB sensor is open to the air. It senses the difference between the exhaust oxygen content and the oxygen content of air.
Click to expand...

Do you have a part number for the loan sensor and a schematic of the controller box???:bounce:
 
Hey Bullshark, there's an wideband O2 sensor that delivers an output GM would understand. Do you think those are more accurate or provide any benefit?
 
Jsup said:
Hey Bullshark, there's an wideband O2 sensor that delivers an output GM would understand. Do you think those are more accurate or provide any benefit?
Click to expand...

Jsup, I recall reading about this awhile back when I was formulating my opinions wrt the old GM.....err....stuff. ;) It is my understanding that this approach involves reconditioning the UEGO output signal so as to be compatible with the 0-1 volt GM ECU hardware input range. It also involves reprogramming the ECU's bin file to now read and interpolate the new linear 1-0v range. This kills all the signal resolution and is much more sensitive to signal to noise. I seem to remember reading about one aftermarket signal conditioner that incorporated inverting the signal to effectively get a 2 volt range, but this is still not that much better and is not near as good as the 0-5v standard. Yes, better than the narrow band HEGO, but still half azzed.:skeptic: I admit I am not up to speed on the latest so shootin from the hip :hunter:

Bullshark
 
Bee LEE Vit or Not....I can read MOST of those schematics and make some sense of them....

I had thought about doing just exactly the same thing to the GM computer, and going all that route....but in practical reality....

What I was fighting was that raggedy assed idle combined with a ignition problem finally solved with ceramic plug boots.....

that raggedy idle was water in the gas....still dunno HOW, just is/was....

car runs fine...NOW...so the questions now are just what increased performance or fuel economy can I expect by upgrading to brand X computer, and IF I did so, maybe to go to a LT1 computer, say '96 or so....sequential, aluminum head 355, same induction I have now....I can make cam/crank sensors easy enough... so what are the gains???

:fishing:
 
heated O2 Sensors

Hi Gentleman,not sure if this is the right way to go about asking questions about O2 sensors,but can somebody tell me where I can get a heated sensor that is OK for my 1984 Corvette.I have purchased some from the USA,but they seem to make my engine run real rich all the time.They are Denso part No234-2000,I was told that these would do the job,but they don't,gone back to the original single wire one.
Thanks for any help offered.
Gordon
 
Over here, Bosch is selling # 13190 heated normal O2 sensor....about 60 bux, last I remember, I have on on my pass side header collector for years now...

:)
 
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