ok so i'm trying to get tuned next week and am pretty sure the tuner I'm going to use puts the wideband sensor in the muffler outlet. I was thinking that putting the sensor in the downpipe would be far more accurate. So I am thinking of putting an extra bung in my downpipe before I hit the dyno. Anyone tried using the sensor in both locations and seen a big difference in AFR readings?

dyno is church's
setup is boosted Y7@10psi

thanks!

 

i have my sensor about 5 inch off the turbo on the downpipe. sensor life is shorter there but more accurate

 

I've noticed a little differentiation in AFR readings from tail pipe compared to DP.... .2-.3 afr. I personally like the o2 in the dp because it gives a more accurate reading of AF/R vs RPM....where as at the tail pipe the reading wont be accurate to the RPM its reading. (understand what Im saying?) basically the time lapse that the gasses take to get to the sensor in your tail pipe throws off your afr/rpm graph.... so when your afr dipped into the 9's it will show on your dyno plot slightly after your power dips.

 

cut and pasted from the DIY techedge website

Remember that the sensor must always be installed with its wires pointing upwards by at least 10° to the horizontal (to avoid condensation cracking the sensor). The sensor should be placed where the gas temperature past the sensor is always less than 750°C but we recommend you install where the maximum temperature is closer to 500°C. This often means the sensor is located at least 1 meter (3 feet) or more from the closest exhaust valve, or a similar distance from the turbo outlet. Never place the sensor on the high pressure side of a turbo setup as this is way too hot and the high exhaust back pressure will give you misleading readings (rich shows richer than it is, so you tune too lean under power - not good for long turbo engine life). Remember that the stock narrowband sensor position will almost always be too hot and a good installation will usually require a new bung be welded in, preferably before the catalytic converter.

Placing the sensor at the back of a vehicle in a tail pipe "sniffing" position can cause the sensor to be excessively cooled unless special measures are taken. We suggest you make a special tail pipe adapter where a 20 mm diameter pipe expand out to 30 mm where the sensor is located, and then closes back to 20 mm. The 20 mm sections should be at least 250 mm long. This setup reduces the gas speed past the sensor and gets the sensor tip out of the direct gas flow without affecting the response speed too much

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RTErnie &raquo;</TD></TR><TR><TD CLASS="quote">I've noticed a little differentiation in AFR readings from tail pipe compared to DP.... .2-.3 afr.</TD></TR></TABLE>

When I go dyno tuning that's about the differnce I notice...most of the time it's like .1-.2. It's not enough for me to be worried about it. If it wasn't accurate I and MANY others wouldn't use it to dyno tune . If you are thinking about it just to get more accuracy, don't worry about it. If it's to keep it there forever, then absolutly. A WB in a DP all the time is by far the best gauge in my book.