Is this a bung for a wideband sensor?

Shadetree930 · 01-04-2009, 03:52 PM

I had the left rear wheel off to do some minor fiddling and noticed this little whozit on my exhaust. Is this a bung that I could use to attach am LM-2 type piece of gear?

RarlyL8 · RarlyL8's Garage

No, the O2 sensor is just north of that nut. Most folks prefer mounting the LM-x sensor after the turbo.

Shadetree930 · 01-04-2009, 05:08 PM

Quote:

Originally Posted by RarlyL8

No, the O2 sensor is just north of that nut. Most folks prefer mounting the LM-x sensor after the turbo.

Darn. So what is it?

mark houghton · 01-04-2009, 06:06 PM

Quote:

Originally Posted by prials

Darn. So what is it?

My guess would be for an exhaust gas temperature sensor. And no, you do not want to put a wideband AFR sensor anywhere prior to the turbo. Too hot; it will toast the sensor is short order (so I've heard anyway). Lots of threads are available on that topic.

DailyDriven'88 · 01-04-2009, 06:42 PM

I believe its a port for a CO tester.

Chuck Jones · 01-04-2009, 06:53 PM

Your LM sensors are inserted into a threaded bung that usually has an allen type threaded insert cap on it that you screw in when you dont' have the sensor in place. Most LM units you buy have a bung included as part of the kit. You just have to have the exhaust pipe drilled and the bung welded in place....in the 3, 12, or 9 oclock position to keep the sensor out of the condensation that can form in the exhaust pipe and potentially ruin your sensor.

RarlyL8 · RarlyL8's Garage

While it is typical to see the LM-x O2 sensor mounted after the muffler I do not believe it is mandatory. The stock O2 sensor is seen in the picture above and is obviously located before the turbo. An O2 sensor is an O2 sensor. It doesn't care what it is hooked to. I have had my AFR O2 sensor screwed into that stock spot for 10 years with no ill results. I have never heard of an O2 sensor fracturing and destroying a turbo but that does seem a possibility.
No idea what the little bung is for. Often wondered myself.

x98boardwell · x98boardwell's Garage

Brian,

I think that spot is for an EGT sensor. They are typically very small.

My question, is I thought that the reason we put the Wide-band O2 sensor after the turbo was because the AFR reading was more accurate that way, not because of the heat.. Is this incorrect? Also, with the stock exhaust and the J-pipe the exhaust is probably not as hot as headers where it feeds right to the turbo in a shorter length tube which may be the reason for the "after the turbo" placement.

Thoughts?

Thanks,
Bryan

mark houghton · 01-05-2009, 08:53 AM

[QUOTE=RarlyL8;4397691] An O2 sensor is an O2 sensor. It doesn't care what it is hooked to. I have had my AFR O2 sensor screwed into that stock spot for 10 years with no ill resultsQUOTE]

I've often wondered at the same logic, but have seen so many cautions from others about these Bosch wide band sensors failing prematurely due to excessive heat. I wonder if that's the nature of wide band, vs. the more robust narrow band O2 sensors?
I still haven't installed my LM2 yet, and would sure like to avoid welding a bung on post-turbo if it's not necessary. You're giving me reason to consider using the bung already installed next to the stock sensor. WTF, the only risk would be the cost of a replacement if it toasted on me.

9dreizig · 01-05-2009, 09:54 AM

Hey don't forget, he's got an 87, which means CAT so the O2 sensor has to be before the cat and after the turbo.. a PIA I'm still trying to figure out where I"m going to put mine.

billjam · billjam's Garage

Quote:

Originally Posted by 9dreizig

Hey don't forget, he's got an 87, which means CAT so the O2 sensor has to be before the cat and after the turbo.. a PIA I'm still trying to figure out where I"m going to put mine.

My $0.02 ... (I am at work and bored!)

On my 86, I have deleted the cat and original narrow-band O2 sensor (hole plugged) and put my wide-band sensor just after the muffler. I couldn't fit it between turbo and muffler and this was only other option.
If it is at the right angle, it can be removed through a 25mm hole in the sheetmetal without dropping the engine.
I played safe and got a bit nervous about putting it before the turbo in the original location (where Rarly has it) due to talk of over-heating and possible turbo damage from a broken sensor. However, this is by far the easiest location for access.

I guess it also depends on whether you need to keep your original narrow-band sensor and cat in place.