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General Wideband gauge reading backwards

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greekgodchaos

15+ Year Contributor
493
107
Jul 4, 2007
Vancouver, Washington
So here's the deal: l have an Innovate wideband setup with a non-Innovate gauge. When the sensor has been calibrated, and gas soaked rag is wrapped around the sensor, it reads as 20 lean; when the rag is removed, it then falls down to 10 rich. I checked the units signal output and it functions properly between 0-5, 0v with a gas soaked rag and 5v with free air. So the gauge is reading the signal backwards...is there a way I can invert the voltage so the gauge can read correctly? I did also buy an Innovate wideband gauge setup and, as you would expect, it works properly. The reason I want to get this issue fixed is so I can have 3 matching gauges...not 1 52mm and my other 2 60mm's.

TLDR
I need a way to invert 5v to -5v, OR, have 0v be represented as 5v, and 5v as 0v.
 
The O2 sensor itself should be altering current flow, not providing a 0-5v signal. The 0-5v is being generated by the gauge (really the controller inside the gauge body) that is reading the changing current flow from the sensor.

What gauge/controller are you using exactly? Have a model number? I assume the sensor is a standard Bosch LSU 4.2/4.9.
 
The 0-5v I'm measuring is coming from the yellow analog output wire from the LC2 unit, which goes to the gauge. The sensor I'm using is a Bosch LSU 4.9, and is set that way in LM Programmer. The gauge I'm wanting to use is a defi wideband gauge, with very straightforward wiring. The innovate gauge reads right no problem, so it's the defi gauge that is reading it backwards.
 
An oxygen sensor does not measure the amount of fuel in the exhaust. When it reads rich that means there is less oxygen in the exhaust and lean is vice versa. That's why when you have a miss fire you go lean. Wrapping up the sensor in a rag soaked in gas does nothing but get gas everywhere.
Now why its reading 10:1 after the rag is removed is weird. I'd suggest putting it in an actual running exhaust stream and then rechecking. Another way to test is to have a container upside down and stick the sensor in it and remove the oxygen inside either with a flame or using another gas to displace the oxygen inside.
 
OK I understand the setup now. I cannot find a manual or data sheet on defi wideband gauges but if you believe inverting the signal would resolve your issue it can be done using an op-amp and some basic supporting circuitry.

A reddit user asked to do exactly what you are attempting, LINK.

As Brian stated above, I would consider running it in the exhaust stream just to rule out any oddities of it being in an abnormal operating condition.

Does the Defi gauge have a controller it can be paired or are you set on the LC2? Not sure if that would help but it is possible the controller the Defi is meant to run with is reverse polarity from the Innovate.
 
The gauge is just a standalone item. My car isn't running at the moment, I am very close to firing up the new engine and I wanted to know that the wideband gauge is working right before I fire it up for the first time. At the moment I am set with the LC-2, considering I now have 2 LC-2 units in my possession.

I should mention that the wideband gauge is a défi knockoff.

As far as that Reddit link, that's basically all Chinese to me. Are there any standalone devices that I can just buy to to invert the signal?
 
Last edited:
An oxygen sensor does not measure the amount of fuel in the exhaust. When it reads rich that means there is less oxygen in the exhaust and lean is vice versa. That's why when you have a miss fire you go lean. Wrapping up the sensor in a rag soaked in gas does nothing but get gas everywhere.
Now why its reading 10:1 after the rag is removed is weird. I'd suggest putting it in an actual running exhaust stream and then rechecking. Another way to test is to have a container upside down and stick the sensor in it and remove the oxygen inside either with a flame or using another gas to displace the oxygen inside.

Actually, the wideband does measure fuel too. At any AFR richer than stoich there is no longer any oxygen in the exhaust to measure.
Kevin Jewer explains this very well on his website.

https://www.sixsigmatuning.com/pages/general-wideband-o2-sensor-info

Jim
 
As far as that Reddit link, that's basically all Chinese to me. Are there any standalone devices that I can just buy to to invert the signal?

I did some googling and I do not see anything that would be an off the shelf device for this application unfortunately.
 
Oh well. I decided to concede defeat and have abandoned the Défi AFR gauge. Ordered a Défi EGT gauge to replace it and a small 2"x1" LCD display for the AFR that works with the LC-2.

Thanks for the input y'all, I very much appreciate your help!
 
Actually, the wideband does measure fuel too. At any AFR richer than stoich there is no longer any oxygen in the exhaust to measure.
Kevin Jewer explains this very well on his


website.

https://www.sixsigmatuning.com/pages/general-wideband-o2-sensor-info

Jim

While that may be correct it would be measuring fuel that is burned not raw fuel. An oxygen sensor is basically an oxygen pump that compares oxygen test sample in the exhaust stream to outside air. I believe that they are galvonic batteries which the amount of air it senses is proportional to the amount of voltage that the battery creates. The processor then determines based on its software what the afr is. They wideband kits are all different flavors and there's many different sensors so mixing parts maybe the cause of issues.
 
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