I have an ETS downpipe, but when I ordered it I forgot to add the wideband bung on. Now I have to remove the downpipe from my car and get the bung weld on, but that's a lot of works. I'm thinking welding o2 bung on my test pipe instead, but a friend of my told me that it reads less accurate on the test pipe. Is that true? Can I just drill a hole on my downpipe without removing it?

 

Ah, I wouldn't worry about it. I mean the best reading is on your down pipe on a 15 degree angle as close to your turbo as safe so... If you have a safe tune you;ll be alright

 

Down pipe afrs are more accurate than test pipe afr readings. By how much, i am not sure.

 

I would be curious to know where you got that information from.

But to answer ThaoDao, it shouldn't make any difference.

 

I'm not sure but another variable could also be the wideband sensor + afr gauge brand. I have the Prosport Halo AFR that came with a Bosch 4.9 o2 sensor. It reads -1 lower than what my tuner was reading. (Ex: on 3rd gear WOT, gauge shows 11.xx and tuner's screen was 12.xx)

Tuner had his sensor on the left exhaust pipe. My wideband is on my DP. I have a MXP short DP

If your concern is geared towards monitoring vs tuning off of your gauge, I would note what your AFR readings are and monitor for changes

 

I welded a second bung into my test pipe for my wide band. I compared my readings to that of my tuner's reading from the tail pipe, the readings were a spot on.

 

Provided there are no leaks before the test pipe, the readings will be accurate, but they may be slightly delayed. On a map with fairly consistent fueling, it wouldn't have much effect.

 

AEM makes a kit where you can just tap in and use a band.