AFR reading and O2 sensor position

[Emanuel]

Hello, does anybody know if there is a relation between WHERE the O2 sensor is placed and the actual AFR reading. Or put in another way, does the AFR reading change putting the O2 sensor closer of farther to the exhaust valve?

In order to get separate readings for left and righr cylinder on my B11 i used the "threaded holes" present in each header, a few inches after the header bend.

Since is a different position than the "usual" on the crossover, I was wondering if the values I get are reliable...

 

[kiwi dave]

I didn't know the B11 came with two Lambda sensors, mine certainly don't. Are you intending to use twin sensors with a power commander and autotune?

You could always try both positions and compare, but unless you have leaks in the exhaust system, I would expect identical results.

 

[Emanuel]

The B11 does not have two sensors.

I am just using two WB sensors and data logging equipment to collect afr data.

 

[PP-1753]

Position is not important. The location of the single Lambda is there because that's where the pipes join and the "average" AFR is read from that point. As you state, using 2 x Wide band Lambdas in the position you do, is probably the correct way to do it - I also know of others who have gone down this road and put in the bungs accordingly.

A single Lambda is always a compromise for fueling, and that is why there is a table in the map to allow for R/H cylinder mapping on its own. Getting it right though is a black art - people have been chasing fuelling perfection for a long time and the results are many and varied.

Let us know your progress, Emanuel.

 

[Ralf Rokita]

The position of the Lambda probe has to generally in a short distance in front of the catalytic converter.
As mentioned from Tony it has to measure the O2 concentration of both pipes after joining.

The other aspect is that there are endotherm reactions in the exhaust gas working between exhaust valves and catalyst. In order to adjust the AFR to Lambda = 1 (and only at this point the catalyst is able to convert NOx vs. HC and CO most effectively, the probe position must be very close in front of the converter.

The tip of the sensor needs to be in the axhaust streaming. Don't recess the tip out of the gas flow!

Best regards,
Ralf

 

[GTM®]

It is recommended to place the 02's as close to the cylinder head as possible, to avoid closed throttle reverse-pulse air contamination. I generally install them within 6-9" off the exhaust port.