Why does wideband need tobe 36 inches down exhaust?

[bob123131]

I have a buddy who owns a small shop, mostly custom european stuff. Anywase i do all my builds there and use his excellent welding skills to my advantage, but he is swearing up and down we should instal my wideband bung 8 inches down from turbo. We already had this fight once and met in the middle at 18 inches and even then it never seemed to read as well as when it was 36 inches away on my first set up. Anyway why is this and how can i explain it to him.

 

[gstryyder]

18-36 inches is recommended by manufacturers for optimum performance... and your sensor last much longer also.

 

[MJBean420]

Burn up the sensor...

 

[anteversion]

It will work at 8 inch of the turbo. But the sensor will no last a mounth on a daily driver car.

 

[donniekak]

It will work at 8 inch of the turbo. But the sensor will no last a mounth on a daily driver car.

Really? I've been putting wb02 sensors in the stock location in cars for years. The first one i did is still working. Many people running aftermarket engine management use the stock location for faster, more accurate readings. I have native wideband support, and do not run a narrow band sensor. If i ran closed loop operation with the sensor 36" doen the pipe, it doesn't cycle properly.

 

[bob123131]

Thats exactly what i don't understand, we do factory replacement of the sensors on some of the european veichles, with a factory wideband and it is the same part number bosch sesnsor. I know in some applications its only like 6 inches down max. I have never had one of these veichles come back in a month with a bad sensor, so what is the reason for the 36 inches and in the last post he said it is more accurate closer, so why wouldn't everyone with the money or a drag only application put them closer?

 

[black_gst]

Mine is in the front o2 location and if you read up in the wiki site for dsmlink you will see that they run theres in the front o2 location for several years with out issues

 

[daren_p]

As said, they recommend the 36" because of the potential heat. Heat will kill the WB sensor faster but as mentioned guys run it in the factory location & seem to get away with it. So its up to you. Closer will give you slightly faster response. Maybe this recommendation came from years back when WB sensor were crazy expensive & guys were trying to get the most life they could out of them?

 

[cbrfrenzie]

Bosch wideband sensors are specified to operate between certain temperatures, pressures and vibration limits.

The common Bosch LSU 4.2 and 4.9 sensors are designed to operate at an exhaust temperature <= 930 deg C (operating) and 1030 deg C (intermitent maxium), Exhaust pressure <= 4 bar, and a maximum vibration of <= 1000 m/s^2.

This has to do with the ceramic heating element inside the sensor, as its the controllers job to regulate the temperature of this ceramic element such that its at a constant 450 deg C. This is needed for the pump cell inside the sensor to either pump O2 in or out of the pumping cell. The amount of effort it takes to maintain a stoich mixture in this pumping cell is measured by the controller, and interpereted as the output Lambda.

Long story short, temperature and pressure affect the output of the wideband sensor, therefore Bosch put "operating condition limits" on the sensor to ensure its outupt is not skewed due to impropper placement or pressures.

Running the sensor too far away could also shorten the life of the sensor, as the heater now has to supply much more effort to maintain that 450 deg C ceramic element temperature, where if the sensor was closer to the turbo, the exhaust heat could do more of the sensor heaters' work, thus lengenthing the life of the sensor! (very minimally though)

Hope this helps clarify the "mysterious O2 sensor placement issues" people argue about!

 

[tsi87889095]

I have mixed feelings on this subject. I think it depends on the brand but my buddy has a 83 fire bird twin turbo with 1600hp and he runs his about 5 inches off of the turbo housing. He has yet to burn one up and he runs the hot rod drag tour which is a 1000miles and drag racing and i think his exhaust would be just as hot as ours if not hotter. I'm not saying any one is wrong with there opinion but this is something i read about all the time and there never seems to be a clear answer.

 

[burkgonzo]

Stock o2 location FTW

 

[jlr2196]

I'm running a Innovate LC1 natively wired into the ecu with the supplied Bosch O2 sensor in the stock location for 6 months (daily driven) without issue.

 

[97gst_spyder]

Mines in the front O2 location wired into the ecu. No problems.

 

[2gGSX]

I always thought it had more to do with the wiring burning up, per the guys from DSMLink:

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In my opinion, having as spot on a reading from the wideband as is possible takes precedence. If you have to second guess your wideband, you're going to have a hard time tuning anything.