O2 Sensor Voltages
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O2 Sensor Voltages
I was wondering for those of you who have tuners or some form of a datalogger... What sort of Voltages are you seeing from your O2 Sensors at wide open throttle?
On mine I see 0.86 V on the one and 0.89 V on the other at WOT.
Does this seem normal? Please discuss.
On mine I see 0.86 V on the one and 0.89 V on the other at WOT.
Does this seem normal? Please discuss.
Elder User
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From: Olathe, KS
To further explain the answer. The sensor is a narrow band. So only reads to about 14.2 to 15.7 Google it for an accurate chart. Power is made in a range from about 12.2 to 13.5 depending on the motor. So the sensor is useless to tell you anything. A wideband is required to read that. There are some out that will go in place of stock, provide narrow band readings for the system and provide a display or datalog for the user.
Bear in mind that wide bands will have errors as well. The industry will not admit that many factors can and do make the O2 inaccurate at times.
Bear in mind that wide bands will have errors as well. The industry will not admit that many factors can and do make the O2 inaccurate at times.
Hotshot
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From: St Louis
Well, actually, I was referring to the fact that O2 sensor signals are used during closed loop operation only. At WOT, the PCM switches to open-loop operation. Hence, the sensor signals are not relevant during WOT periods.
However, it is normal to see voltages greater than 0.6V during WOT since, with the throttle open and the injectors at or near maximum pulse-width, the exhaust will be quite rich.
Steve
However, it is normal to see voltages greater than 0.6V during WOT since, with the throttle open and the injectors at or near maximum pulse-width, the exhaust will be quite rich.
Steve
Last edited by projectSHO89; Oct 15, 2007 at 07:16 AM.
Elder User
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From: Olathe, KS
Hey Steve, I was just reinforcing the reason it is ignored at WOT for advocate.
advocate
I could not paste the chart. So the link will show a A/F ratio chart for the narrowband o2.
http://home.netcom.com/~cmathes/air_fuel_ratio.html
quote "Note that the enrichment becomes fairly compressed at higher voltages i.e. small voltage changes = large ratio changes."
Here is a DYI site that has some really good info about engine management if you wish to browse. The box is short on CPU power which caused challenges for me with coding and sample rates. That was 2002-3 so a lot has changed. The features are pretty sweet.
The knowledge collected is outstanding for learning about fuel management.
http://www.megamanual.com/v22manual/mtune.htm#theory
And the forum for the site.
http://www.msefi.com/
advocate
I could not paste the chart. So the link will show a A/F ratio chart for the narrowband o2.
http://home.netcom.com/~cmathes/air_fuel_ratio.html
quote "Note that the enrichment becomes fairly compressed at higher voltages i.e. small voltage changes = large ratio changes."
Here is a DYI site that has some really good info about engine management if you wish to browse. The box is short on CPU power which caused challenges for me with coding and sample rates. That was 2002-3 so a lot has changed. The features are pretty sweet.
The knowledge collected is outstanding for learning about fuel management.
http://www.megamanual.com/v22manual/mtune.htm#theory
And the forum for the site.
http://www.msefi.com/
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Wow thanks for all the issue guys. With all the things I am learning on this thread I will have to take the whole week off for learning things!
I just figured that I was maybe too rich. I remember before that at WOT i would be around .7X V and now I am at the end of the scale right below .9 V. But since the computer does not use O2 sensor readings at WOT I do not know for sure now... My tailpipe does look a little black, before I was sure that it wasn't like that.
I heard that O2 sensors will "slide" rich when they start to go bad, so that was my reasoning behind this.
I just figured that I was maybe too rich. I remember before that at WOT i would be around .7X V and now I am at the end of the scale right below .9 V. But since the computer does not use O2 sensor readings at WOT I do not know for sure now... My tailpipe does look a little black, before I was sure that it wasn't like that.
I heard that O2 sensors will "slide" rich when they start to go bad, so that was my reasoning behind this.
Elder User
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From: Olathe, KS
btw, What is the vehicle?
It possibly is rich, I understand Ford tends to be well on the rich side at WOT anyway. I am working up a Wide Band for my truck now. With the Sniper special forces tuner I just purchased, I have the ability to richen or lean So am eager to see where it is at. Had an ex manifold off recently and appears to me to be plenty rich. Even with the wide band I still take the results with a grain of salt. It is very easy to fake out the o2.
During cruise it the o2 should be within the chart. Does not mean the o2 is good. just that the system is correcting properly to the o2 reading. The o2 also needs good airflow so idle can be misleading.
The sensors usually do "slide" rich. Primarily cause they get clogged up.
Happy reading
It possibly is rich, I understand Ford tends to be well on the rich side at WOT anyway. I am working up a Wide Band for my truck now. With the Sniper special forces tuner I just purchased, I have the ability to richen or lean So am eager to see where it is at. Had an ex manifold off recently and appears to me to be plenty rich. Even with the wide band I still take the results with a grain of salt. It is very easy to fake out the o2.
During cruise it the o2 should be within the chart. Does not mean the o2 is good. just that the system is correcting properly to the o2 reading. The o2 also needs good airflow so idle can be misleading.
The sensors usually do "slide" rich. Primarily cause they get clogged up.
Happy reading
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It's a 2003 F150 Supercrew Lariat with the 5.4L. I am using a Diablosport Predator and it does seem to show a lower voltage at WOT compared to what I was seeing with the factory tune loaded. Everything is stock on the truck other then the tuner and I replaced the 4 cats (they were melted/clogged) with 2 high flow magnaflows and put on a dynomax super turbo muffler in the stock location.
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Elder User
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From: Olathe, KS
Regrettfully not familiar with your tuner. It may have added fuel... One way to estabilsh if it the o2 is changing would be to put the stock tune back in for a run to measure it. If it goes back toward original readings you know it is the tuner adding fuel. They would do that to be "SAFE" with the motor. Not always in your best interest. The tailpipe change is a definite fact to be investigated. If the tuner has fuel control then a run on a dyno where they have a sniffer and someone who can tune is in order.
Did you look at the o2 sensor chart? Bigger question is did it make sense??? What the chart does not show is affect of temp change on the o2 as well. the only area of any accuracy is the center of the graph. On the edges it is a very course reading. then factor that the o2 changes with temp variations, consistancy goes away. Your exhaust changes will affect flow, pressure and temp. All three of which can alter the chart.
Did you look at the o2 sensor chart? Bigger question is did it make sense??? What the chart does not show is affect of temp change on the o2 as well. the only area of any accuracy is the center of the graph. On the edges it is a very course reading. then factor that the o2 changes with temp variations, consistancy goes away. Your exhaust changes will affect flow, pressure and temp. All three of which can alter the chart.
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