WB AFR shows something differnet to O2's
Thread Starter
TECH Resident
Joined: Aug 2003
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From: England UK
WB AFR shows something differnet to O2's I've noticed something since I've played with idle timing. I wanted the car to sound lumpy on idle. Have around 20 degrees of idle timing, runs fine
Now normal driving I see my O2's ocilating, and WB AFR showing around 14.6. If I go WOT I see what I expect, O2's around 900mv and WB around 12.5 AFR.
Now the odd thing, in idle O2's are occilating, but WB shows 17. Now I can smell its rich, due to timing, if I turn timing back both types of sensors show simular results.
Its like the WB is giving an odd reading of unburnt fuel, but O2's things things are good. Does O2's measure oxygen in the exhaust and WB measure some other gas? because they must be measuring something different, they are only 2 inches apart.
Now normal driving I see my O2's ocilating, and WB AFR showing around 14.6. If I go WOT I see what I expect, O2's around 900mv and WB around 12.5 AFR.
Now the odd thing, in idle O2's are occilating, but WB shows 17. Now I can smell its rich, due to timing, if I turn timing back both types of sensors show simular results.
Its like the WB is giving an odd reading of unburnt fuel, but O2's things things are good. Does O2's measure oxygen in the exhaust and WB measure some other gas? because they must be measuring something different, they are only 2 inches apart.
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Joined: Aug 2004
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From: Portland Oregon
O2 and WB are the same type of sensor, they sense the same thing. You said you smell it's rich, can it be so lean that you are smelling burnt fuel. Really lean may smell like fuel. ???
I have the opposite puzzle at idle. My O2's think it is lean and the STFT keep adding fuel until the WB is showing 12.2. I believe the WB is accurate, but why do the O2's think the idle is lean? I think the O2's don't get a strong signal at idle, and they get confused.
I have the opposite puzzle at idle. My O2's think it is lean and the STFT keep adding fuel until the WB is showing 12.2. I believe the WB is accurate, but why do the O2's think the idle is lean? I think the O2's don't get a strong signal at idle, and they get confused.
Thread Starter
TECH Resident
Joined: Aug 2003
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From: England UK
17 is very lean shown on my WB, it does this in idle, however my O2's are occilaing, although not a perfect wave form. They are Bosch 13111's, I have LT headers. The WB is next to the narrow band, as i have no cats. So the smell at 17 AFR smelling rich to me, i know its lean, but perhaps I cant tell the different in smell. Smells good 
, gives a good headache in traffic.
Car runs good driving at low RPM, I see narrow bands occilating and WB occilating around 14.6.
I'm wondering is there is a difference in sensor performance, as low RPM,s there isn't a lot of exhaust gas, perhaps norrow bands are good at low exhast flow and the WB needs a little more.
, gives a good headache in traffic. Car runs good driving at low RPM, I see narrow bands occilating and WB occilating around 14.6.
I'm wondering is there is a difference in sensor performance, as low RPM,s there isn't a lot of exhaust gas, perhaps norrow bands are good at low exhast flow and the WB needs a little more.
What are the STFT and LTFT's doing.
The WB will still read accurately, at least not off too far, at idle.
All non-catted cars stink, we are all used to the cats doing their job of cleaning the exhaust gases up.
Post your tune and a log file.
The WB will still read accurately, at least not off too far, at idle.
All non-catted cars stink, we are all used to the cats doing their job of cleaning the exhaust gases up.
Post your tune and a log file.
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Launching!
Joined: Dec 2005
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From: nj, edison
neither sensor is going to be accurate at idle with a larger than stock cam and narrow lsa {108lsa-112lsa] . the wb will oscillate much less than the nb at idle, but it will read artificially higher. this condition is due to reversion.
mine shows an avg. of 15.5 and a low of 14.7 and high of 16. a motor can tolerate leaner conditions at idle. you could let it idle for a while an ck. the plugs to see how clean they look. I'm not sure if the plug condition will be accurate at idle. if you had an egt probe it would be another parameter to more accurately and safely tune idle.
the way i tuned idle was to simply monitor vacuum and tweak the afr up and down with real time feature{binary controls}. i believe the vacuum will drop a hair as you lean it out.
what is baffling, is that when under real time control the wb afr stays flat to what ever value you command. one other factor you could use to determine how lean you are is to measure ect rise time.
mine shows an avg. of 15.5 and a low of 14.7 and high of 16. a motor can tolerate leaner conditions at idle. you could let it idle for a while an ck. the plugs to see how clean they look. I'm not sure if the plug condition will be accurate at idle. if you had an egt probe it would be another parameter to more accurately and safely tune idle.
the way i tuned idle was to simply monitor vacuum and tweak the afr up and down with real time feature{binary controls}. i believe the vacuum will drop a hair as you lean it out.
what is baffling, is that when under real time control the wb afr stays flat to what ever value you command. one other factor you could use to determine how lean you are is to measure ect rise time.
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