I am just finishing up my downpipe and before I send it off to get it coated....where should I weld the bung for the wideband O2 sensor? Stock location right in front of the cat? A little after the turbo? This is a speedpro unit + wideband. Thanks for the help.

Jason

 

I usually mount them as close to the turbo as you can get and still have easy access. This is generally within 10" of the turbo.

 

from the techedge website, http://www.techedge.com.au/vehicle/wbo2/default.htm
Wideband Sensor Positioning
The wideband sensor must be carefully placed in order to prevent damage to the sensor itself. Also, if you use the sensor's output directly to drive your ECU then you should be doubly careful. Please follow all of these "rules" :

The sensor should always be placed on the engine side of a catalytic converter, unless you are testing the effectiveness of the convertor itself.
The gas temperature to the sensor should never exceed 850 degrees C (about 1560 degrees Fahrenheit).
The sensor should never be run without power to the WB unit (a hot sensor burns off carbon residues)
Always have the long axis of the sensor perpendicular to the gas flow (stops sensor clogging)
Position the sensor vertically or at most between 10 o'clock to the 2 o'clock position (this avoids cracking the internal ceramic structure should moisture condense internally)
The sensor reads the partial pressure of gases in the exhaust and infers the AFR, rather than by measuring some magical AFR directly. This may be an issue on forced induction, and in particular, on turbo-charged engines.

AFRs will indicate richer than they are, causing you to run leaner than you think.
Lean AFR's will be richer (or less lean) than indicted.
A solution is to ensure you locate your sensor away from the turbo, and certainly on the exhaust (low pressure) side of the turbo rather than the engine side.

 

youre saying that the improper mounting of the sensor will have the sensor output a signal to the control saying an overly rich condition when that is not in fact the case?

edit: i just read the techedge site, it makes sense b/c the pressure differences are to blame for the fualty reading.

just keep it reasoanbly close to the turbo, but after, simple enough. I think the reason tony doesnt have a problem is because the turbo is actaully a "sink" for thermal energy, so by the time the exhaust gasses leave the turbine they are much cooler than on the other side.


[Modified by FFgeoff, 10:01 AM 1/6/2003]

 

Tony1:

My stock 1-wire is about 3" from the turbine. Too close for WB? Thanks.

 

we run it pretty close like that on our race car and it seems to work fine.

 

it shouldnt be too hot immediaetly after the turbine because the turbine itself is a thermal "sink" and sucks a lot of heat energy away from the exhaust gasses. By the time the air has left the turbine it has already cooled down a ton, using the heat to spin the turbo.

 

my friend put his wideband o2 at the end of his downpipe and has experienced carbon fouling. He has had to replace his wide band o2 sensor three times already.

 

did he ever have the o2 in his downpipe with the controller disconnected? that is the usual cause for carbon fouling. if the sensor isnt active, it gets fouled

 

this sensor was from the Speed Pro ECU, so it was constantly on. it was a street car with large injectors, so it was probably running rich during normal driving. When you took out the sensor there were visable carbon deposits on the sensor. On another car with Speed Pro, the sensor was placed about 6 inches from the turbine, and that sensor was always clean. That is the original sensor from 98' with lots of daily driving & race gas use and has yet to be replaced.

 

Is this position where the "X" is ok? It is about 4 inches from the turbo.


Thanks, Jason

 

yeah, it looks fine, thats where i have mine, have a look..

 

That position is fine. I have mine about 2" further down, right at the first bend of the downpipe.

 

That's pretty close, would be nice for a race car. Mine was about that close and became welded in after about 10k miles. You want it as close as possible, but with a need to minimize welding, I was told to put mine between 10-18 inches away. Mine is currently about 10 inches away.....

 

Oh man Sweet!!! My one wire is in about the same spot!! This is where I am going to put my WB. Thanks!!

 

Sweeet. Thanks alot guys.

JAson