Hello. I am wanting to know what difference is there in AFR when changing wideband sensor location from near the header to close to the tailpipe. Will the sensor read richer in the tailpipe compared to closer to the header or is it the opposite?? I am just asking for knowledge because after searching couldn't find an answer. Looking forward to any helpful responses, thanks.

 

Really hard to tune a car from the tail pipe if the exhaust has a catalytic converter installed. AFR's will be off/leaner!

Without a catalytic converter in the exhaust. The AFRs could also be leaner if there is any sort of leak in the exhaust piping or there is a back draft of fresh air getting into the pipe and reaching the WBO2S. Other wise the AFR should be the same.

The difficulty in tuning via a tail pipe mounted wideband O2 is the longer distance from the combustion process. Meaning the time it takes for any changes you make in the fuel or ignition maps to travel the length of the pipe and reach the sensor are longer. Unless you calculate for that distance any changes you try to make will take time to read on your computer.

If I remember correctly there are tuning software applications that will make the adjustments based on the WBO2 location. I can't remember what tuning software/hardware it was, Innovate maybe??

 

Thanks for the response. So that means the closer i move the sensor towards the headers, the richer reading they'll show? For example when street tuning with sensor very close to the headers, if i want an actual afr of 13.0, i should be tuning for around 12.0 afr on the wideband? Again thanks for the help.

 

Not really, It means that the closer the sensor is to the combustion chamber the faster you will see accurate data/AFRs on your datalogs. If you are using live tuning, the changes you make will be seen right away if you use the stock O2 location. if you use it in the tail pipe you will have to wait a few seconds for the wideband to read those changes. If you want an AFR of 13 you tune for 13, no matter where the O2 sensor is in the exhaust.

That is, unless you have a catalytic converter in between the combustion chamber and the wideband sensor. Then yes there would be a difference of AFR. How much of a difference depends on how well your catalytic converter is working. I have read articles that say it can be between 0.5 - 1.00 AFR leaner. So if you were tuning for 13:1 you would want to see 12.5:1(12:1) I have never actually tuned an engine with a wideband after the cat. So I am not 100% on these numbers.

 

Okay thanks for clearing that up. So when tuning individual cylinders, the sensor is right in the header which is pretty close to the exhaust ports. So i would be aiming for the same afr as if having a single sensor located 18 to 30 inches down the exhaust pipe?

 

I am going to assume that you only have the one O2 bung in the header. Do not tune individual cylinders with a stock O2 sensor location if it is located in the header primary tube close to the cylinder. That will only give you AFR's for that one cylinder not all 4.

If you want to get the best all around tune using one wideband sensor, you want the sensor in the header collector. where all 4 cylinders merge into one. The AFRs will be the same in this location. If you want 13:1 tune for 13:1, again, do not use the individual cylinder tuning.

In order to do individual cylinder tuning you have to install an O2 bung on each of the 4 primary header tubes and read/tune each cylinders AFRs with a wideband sensor individually. Not that it can't be done, but with only one sensor it will take some time!

 

and its not necessary unless you tuning a nascar motor or something

what wideband you using?
sensor placement also affects the sensor life.
i know lol i have 3 dead sensors already

 

I am not tuning individual cylinders. I was just wanting to know whether the sensor gives false readings if it is too close to the exhaust ports, since when tuning individual cylinders(which i'm not) each sensor is in the header too close to the exhaust ports.

 

If it is in the stock location, you will be fine. Only thing that would happen if you put it closer,would be that you could overheat the sensing element in the O2 sensor.

AFRs will not change because it is closer or further. Only thing that could alter the AFRs in the exhaust would be a crack or leak in the exhaust pipe or a catalytic converter.

 

Okay great. Thanks for helping out and making things clear.