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Discussion Starter #1
Hey guys.

Looking to find a method to validate the accuracy of my wideband o2 sensor.

Possibly using nitrogen as a zero reference and some form of verified test gas of a 10.0:1 fuel mixture.

Does anyone know if / how the manufacture actual QAs the accuracy of these sensors etc ?

Cheers :)
 

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Discussion Starter #4
A free a calibration is pretty much useless. How do you know these sensors don't drift / deteriorate over time?

I am looking at getting a test gas mixed by BOC but know what the mixtures needs to be for a 10:1 AFR.

Or how the little analyser even works. IE - The wideband itself just measures oxygen ? then goes into the controller that applies some equations to determine Lambda ?

In which case would i need a Ratio mixture of Exhaust gas to air OR a mixture of a certified amount of o2 that would equate to a ratio of exhaust mixture etc
 

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A free a calibration is pretty much useless. How do you know these sensors don't drift / deteriorate over time?

I am looking at getting a test gas mixed by BOC but know what the mixtures needs to be for a 10:1 AFR.

Or how the little analyser even works. IE - The wideband itself just measures oxygen ? then goes into the controller that applies some equations to determine Lambda ?

In which case would i need a Ratio mixture of Exhaust gas to air OR a mixture of a certified amount of o2 that would equate to a ratio of exhaust mixture etc
the oxygen content outside of your exhaust is pretty constant and thats what you need, not 100% pure o2 your looking to get a baseline for outside air, using that as a baseline it works more like a scale or transducer by setting its baseline at "100%" lean or outside air and then goes down from there to give you the proper air fuel ratio by the lack of said oxygen and assuming that the replacement for the oxygen would be hydrocarbons.

Do these sensors drift? very possible, however you would notice it in your tune if the sensor started trending leaner as if your tune stayed constant but your sensor was telling you were lean across the board obviously your sensor would be faulty.
 

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Discussion Starter #6 (Edited)
If i were tuning a engine with over 20k invested in it.... i would want some confidence that the lambda sensor is showing me real numbers.

Does anyone know what the makeup of exhaust gas actually is? mainly carbon monoxide i assume


Or i was thinking in using a certified mixture with Air displacer (Butane) vs Air of a 10:1 ratio ?
 

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If i were tuning a engine with over 20k invested in it.... i would want some confidence that the lambda sensor is showing me real numbers.

Does anyone know what the makeup of exhaust gas actually is? mainly carbon monoxide i assume


Or i was thinking in using a certified mixture with Air displacer (Butane) vs Air of a 10:1 ratio ?
How about talking with a professional that works with engines of that caliber and above to see what they might recommend if you don't trust your equipment?

IMHO, tuning an engine an that you have that amount of money into and only relying on a lambda sensor to tell you what is going is a bit foolish.
 

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If I had a 20k motor I think I'd have a few bosch lsu 4.2 sensors laying around in case I had a suspicion that one was going bad.
 

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Discussion Starter #11
Validating against another sensor doesn't really prove much.

Ideally the best way will be to validate against a traceable calibration gas. Just need to find out what can work to give a known lambda reference
 

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If i were tuning a engine with over 20k invested in it.... i would want some confidence that the lambda sensor is showing me real numbers.

Does anyone know what the makeup of exhaust gas actually is? mainly carbon monoxide i assume


Or i was thinking in using a certified mixture with Air displacer (Butane) vs Air of a 10:1 ratio ?
its a very simple system and it does work well, by knowing how much oxygen is in the exhaust you can calculate the ratio of oxygen to fuel is in the engine.

Look at what steve morris or nelson uses on there engine dyno's to tell the lambda of fuel in the engine and replicate that. From what ive seen, they use standard afr gauges one on each exhaust header to tell general AFR and egt thermocouples on each exhaust runner to make sure each cylinder is hitting correctly.

In fact its much better to have both rather than one or the other. With an AFR gauge you can tell that your injecting the "correct" amount of fuel, or the amount of fuel you want. However if you know the temperature of the exhaust then you know if your too hot, too cold, detonating or missing/breaking up. By datalogging these values you can easily see an off trend from the afr gauge, especially if you have two afr gauges. Chances of both sensors drifting at the same rate at the same time is near zero when they are on separate banks.

As far as calibration goes, i have never heard of a calibration gas being used like a halogen gas tester. I think one of the reasons is because free air is a very good calibration tool, instead of calibrating at 10.00 or 14.7 your calibrating at the far end of one range and then going down from there as far as oxygen content goes. However if you were dead set on calibrating the unit at a set lambda you could possibly do it in a closed chamber or vessel and adding the correct weight/amount of oxygen/inert gas to fit the desired ratio. an easier way would be to fit a small long tube with a propane burner and adjusting the oxygen inlet until it reaches your desired afr ratio. And in order to find that correct ratio, you would need to purchase a separate instrumentation grade gauge (or another brand new afr gauge just to set the burner correctly) and then set your air/fuel mix and insert your old afr gauge into.
 

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OP isn't too far off. The way it's done is typically with a calibration gas in a lab test cell.

The thing is, it's not the sensor's cal that's being calculated, it's the controller. With consumer grade stuff, the cal curve of the controller is fixed. With the high end labratory/test/motorsports stuff (we use a McLaren system at work) the calibration curve is derived based on the test bench and programmed into the controller. There's not really a DIY way to test, and that's why you'll only find it at pretty high levels of development and testing (i.e., manufacturers). The free air cal is about the best you can do, with the issue being that it only clamps one end of the curve and applies an offset. The newer 4.9 sensors use a different type of measurement though and do not use a free air calibration... if you're shopping around for a new wideband you really shouldn't be looking at anything that still uses a 4.2 for this and several other reasons.

The sensors are very consistent. If you have any doubt in it, the best thing to do is just replace it. Bosch LSU 4.9 sensors are rated (in high performance applications) for 500 hours in unleaded fuel or 50 hours in leaded. For normal street cars the life expectancy is up to 100k miles.

If you have $20k invested in an engine, risking your investment over a $40 sensor is silly. You just replace at the correct service intervals based on the specs of the sensor (or if you have any doubt based on high exh temp running, damage, etc.) and call it a day.
 

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Discussion Starter #15
Excellent reply Spadam & cervan !!

To me there is a difference between a validation and calibration - being that a validation is simply checking something against something else that you have absolute confidence in.

In this case Checking the o2 sensor / controller against a certified test gas of 10.0:1. Calibrating would imply that we apply a correction to the instrument under test (sensor/controller) if there is a substantial bias. We know that cheap (in comparison to industrial grade) electronics do not have this capability (zero trim only, not multi-point trims) so we would just replace the sensor and repeat the process.

However doing the bump validation would give us confidence if the sensor is reading accurately or not. Last time i checked no one ever supplies a calibration certificate with automotive instruments ?

I can quite easily and affordably get some calibration gas mixed up from BOC, however knowing what the makeup would be to give me say a 10.0:1 mixture is the issue.

Say a ratio of 10:1 Carbon monoxide to air ?
 

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I thought it was seemly the amount of oxygen left not what else was in the mixture.
Isnt that what the wideband is doing?
So if you had a seal box and pump in oxygen it should go full lean.
Then if you suck some out and pump in any other mixture shouldnt it start to read richer?
 

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I thought it was seemly the amount of oxygen left not what else was in the mixture.
Isnt that what the wideband is doing?
So if you had a seal box and pump in oxygen it should go full lean.
Then if you suck some out and pump in any other mixture shouldnt it start to read richer?
the sensor reads oxygen left over in the exhaust stream to give you the afr reading so technically yes you could put the sensor into a vacuum and it would read full rich.

I didnt know you had the ability to get test gases made for you, i would suggest 12 or 13:1 instead of 10 as that is the very far end of the spectrum and would give you very little information as to if you were too rich it would still read just 10:1 (unless your gauge can read below 10:1)
 

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If its any peace of mind for you, Ive been using the same sensor for over 4 years now. Even with leaded fuel from time to time. I have the AEM, I let it warm up before every start.
 
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