Question #3,980,134 for Steve

[wurk_truk]

OK.

I wish to learn a bit on HOW the O2 feedback system works.

06-08. Lets start there. A Nernst cell O2 sensor MAKES its own voltage. 450mv is Stoich/14.7AFR, right?

So, In MY mind... the O2 is a simple 2 wire, with one wire being the reference wire and the other being the return from the O2. And... as the O2 changes, so does the voltage on the output wire. Lean 200mv. Rich 800mv, etc. Right? So, then how does the CLB offset work? In MY mind, I always thought that the reference wire had some voltage placed upon it and the O2 sensor added to it. How else are we able to 'drive' an O2 beyond its means? I guess that could be done from the output side as well. This IS DC voltage (0-1vdc) and THINK voltages can be added, just like 2-12vdc batteries outputting 24vdc when in series, right? We drive the second battery to 24vdc simply by applying 12v to the negative terminal.

So, if we add in 200mv on the reference wire to both O2s, NOW the 450 is added in and the ECM 'sees' 650, all the time the O2 is still 'saying' 450... 450...450... right? (but by us adding that 200mv in the system... we ARE driving that O2 further to its edge of 800mv, right?)  Or. conversely, we could make the output wire always have 200mv on it, and the O2 pushes its own 450, etc into the system.  Either way, the reference will see 650.  (actually THIS sounds more likely as this would really push the nernst cell's voltage up.).

I THINK I am correct on this but await an answer before I ask the REAL question (dealing with 09 up sensors). I want to be sure my thoughts are correct before I go further.

TIA

[FBRR]

I'll let Steve answer most of your question, however, with regard to CLB, THAT is NOT added to the "reference voltage" of the O2 senosr. That is a software function to "decide" the voltage point between RICH and LEAN. While 450 is the mean value for "stoich", the CLB is merely an offset applied in the software to decide when to change STATE between rich and lean.

So if the "switchpoint" is left at 450, anything above is RICH and anytime the O2 sensor reading goes lower it's "LEAN."
So you have "closed loop" about the 450 volt point in sensor reading output! When you "add" a CLB ( closed loop bias) voltage, all you have done is change the point where the software "decides" to go RICH or LEAN. Add 200 and the system will not recoginze the O2 voltage is RICH until the sensor output is greater than 650 (450+200). But you have not added that in any REAL sense, just changed the point in SOFTWARE when the closed loop fuel control makes corrections!

When you choose a value greater than 450, the system is biased on the RICH side. A fuel correction will not happen until the O2 sensor signal "has already been rich" for some amount of time crosses the switch point voltage (450+CLB)! So the system is slightly richer "longer" before a fuel control change in state occurs. And conversely, when the system is RICH state ( above the 450+CLB offset) and the fuel control drives the system "lean", the real A/F ratio is still on the RICH side of stoich (at 650 setting) when the fuel control senses "lean state", switches RICH again". That is how the CLB biases fuel on the RICH side. All you are changing with the CLB is the sensor voltage point where the software fuel control changes state from RICH to LEAN and LEAN to RICH. ( quickly, fuel is always being ADDED and SUBTRACTED by the fuel control based on "O2 sensor" output. When the system STATE "reads RICH"/ the sensor voltage is above the switchpoint! and fuel is removed, when the system state "reads LEAN"/the sensor voltage is below the switchpoint and fuel is added!

So while the "table value" for CLB is "voltage", that value is not a real voltage offset, but is added by the software to the SWITCHPOINT for closed loop fuel control, to decided when the system is rich ot lean. ( The raw O2 sensor signal is un affected by any changes to CLB! It is only added in the software when calculating the switchpoint)

I tried to explain this (CLB offset votage) in several ways in the above, for explaination in how the CLB is used.
(Fuel control is a little more complicated than the examples used, but you get the point)
Hope that helps!

[HarleyFranco]

wurk_truk,

I like to think of the clb as the working voltage of the O2 sensor.  All it is is a switch, if you supply more working voltage it will switch at a richer air fuel value, and if you supply less voltage it will switch at a leaner air fuel value.

Hope this helps.

Frank

[strokerjlk]

I tried to explain this (CLB offset votage) in several ways in the above, for explaination in how the CLB is used.
(Fuel control is a little more complicated than the examples used, but you get the point)
Hope that helps!

you did fine. hang around more, some of us look forward to your knowledge.
thanks 

[wurk_truk]

  100%.  I really enjoy your posts and learn quite a lot.

Crap... I DO get it.  We aren't driving the NB O2s dead with added voltage... we drive em dead because we make them live at 700+ voltage (from the nernst cell) because we WAIT (with software) until they will toggle closed loop at THAT point, instead of 450mv.

Got it!!!  Thank you very much.

Now, maybe you can answer another question.  Starting with 09 touring and going to 11 touring bikes, Harley Davidson changed something.  When we data log from the ECU, as opposed to logging the ACTUAL voltages from the O2s, we NOW see a 900mv offset.  Instead of reading 450mv, the ECU reports 1350mv.  And... adding a CLB to that it is easy to log +1500mv .  Would you know 1) is THAT voltage all internal to the ECM? And is simply how it is logged thru the ECM?  2) and do the NB O2s STILL only output 450mv at 14.7 with an offset like this??

(I haven't logged, nor checked O2 voltages on a 10 bike as of yet.  And...  I do NOT have analog loggers, just digital loggers from work.  But... MY view is a nernst cell is a nernst cell and 14.7 IS 450mv.)

TIA.

[FBRR]

Wur_turk,
Those changes in the "O2 sensor" readings over the years are due to ground potential offsets.

The "Other" change between model years, is some are based on "Air/Fuel" as table values so "mean .450" is Stoich A/F,
which changes with fuel! And later years the fuel control is based on "Equivalence ratio". Where an Equivalence ratio of 1.00 equals STOICH! It's a software change that makes using Ethanol fuel mixtures easier to comprehend from a calibration point.

[ViennaHog]

I'll let Steve answer most of your question, however, with regard to CLB, THAT is NOT added to the "reference voltage" of the O2 senosr. That is a software function to "decide" the voltage point between RICH and LEAN. While 450 is the mean value for "stoich", the CLB is merely an offset applied in the software to decide when to change STATE between rich and lean.

So if the "switchpoint" is left at 450, anything above is RICH and anytime the O2 sensor reading goes lower it's "LEAN."
So you have "closed loop" about the 450 volt point in sensor reading output! When you "add" a CLB ( closed loop bias) voltage, all you have done is change the point where the software "decides" to go RICH or LEAN. Add 200 and the system will not recoginze the O2 voltage is RICH until the sensor output is greater than 650 (450+200). But you have not added that in any REAL sense, just changed the point in SOFTWARE when the closed loop fuel control makes corrections!

When you choose a value greater than 450, the system is biased on the RICH side. A fuel correction will not happen until the O2 sensor signal "has already been rich" for some amount of time crosses the switch point voltage (450+CLB)! So the system is slightly richer "longer" before a fuel control change in state occurs. And conversely, when the system is RICH state ( above the 450+CLB offset) and the fuel control drives the system "lean", the real A/F ratio is still on the RICH side of stoich (at 650 setting) when the fuel control senses "lean state", switches RICH again". That is how the CLB biases fuel on the RICH side. All you are changing with the CLB is the sensor voltage point where the software fuel control changes state from RICH to LEAN and LEAN to RICH. ( quickly, fuel is always being ADDED and SUBTRACTED by the fuel control based on "O2 sensor" output. When the system STATE "reads RICH"/ the sensor voltage is above the switchpoint! and fuel is removed, when the system state "reads LEAN"/the sensor voltage is below the switchpoint and fuel is added!

So while the "table value" for CLB is "voltage", that value is not a real voltage offset, but is added by the software to the SWITCHPOINT for closed loop fuel control, to decided when the system is rich ot lean. ( The raw O2 sensor signal is un affected by any changes to CLB! It is only added in the software when calculating the switchpoint)

I tried to explain this (CLB offset votage) in several ways in the above, for explaination in how the CLB is used.
(Fuel control is a little more complicated than the examples used, but you get the point)
Hope that helps!

Great technical explanation and very well written. Thanks