Who Has Cut Down O2 Bungs?

[Ohio HD]

Those that have cut down O2 bungs on their exhaust, did you get any benefit from it at all? I can probably sink my O2 sensors by about an 1/8" into the pipe further. The only thing is it still won't be all the way into the pipe, but it will expose more of it to the exhaust stream. I have to get the tools to cut them down, the largest cutter I have is 0.937", and the OD of the bungs is 1.010". So I wanted to ask if anyone did see any benefit cutting theirs down. If I have to add new locations, I will, but if cutting them might do it, I'll try that first.

[Sporty 48]

Those that have cut down O2 bungs on their exhaust, did you get any benefit from it at all? I can probably sink my O2 sensors by about an 1/8" into the pipe further. The only thing is it still won't be all the way into the pipe, but it will expose more of it to the exhaust stream. I have to get the tools to cut them down, the largest cutter I have is 0.937", and the OD of the bungs is 1.010". So I wanted to ask if anyone did see any benefit cutting theirs down. If I have to add new locations, I will, but if cutting them might do it, I'll try that first.

This little diddy is how I remember it:
Measure 3 times, cut once.
Or was that cut 3 times and it is still too short?
No matter how many times I trim that O2 sensor block (or piece of wood) it is still too short.
Why would you trim anything before you check the spec?

[Ohio HD]

Those that have cut down O2 bungs on their exhaust, did you get any benefit from it at all? I can probably sink my O2 sensors by about an 1/8" into the pipe further. The only thing is it still won't be all the way into the pipe, but it will expose more of it to the exhaust stream. I have to get the tools to cut them down, the largest cutter I have is 0.937", and the OD of the bungs is 1.010". So I wanted to ask if anyone did see any benefit cutting theirs down. If I have to add new locations, I will, but if cutting them might do it, I'll try that first.

This little diddy is how I remember it:
Measure 3 times, cut once.
Or was that cut 3 times and it is still too short?
No matter how many times I trim that O2 sensor block (or piece of wood) it is still too short.
Why would you trim anything before you check the spec?

I know what the spec is, it can't be met with these pipes as built, or most likely by any other pipe on the market. Stock Harley pipes don't meet the spec either.

The 1/8" I can cut from the existing bungs, will still not meet the spec. I'm just trying to ascertain if anyone that has reduced the bung lengths in their exhaust, have gotten any positive results for their tune.

[Evo160K]

Ohio HD,
There have been several threads here that address your question.  You might try the search function.  One discussed a couple of ways/tools to cut the bung down as you're suggesting.  Another started by Steve Cole discusses specifications, it's a very worth while discussion and may include the ways/tools I mentioned.  You might check his threads.

In my case I needed 45 deg, stainless bungs with the exposure required and ended up having them fabricated.

[Ohio HD]

Ohio HD,
There have been several threads here that address your question.  You might try the search function.  One discussed a couple of ways/tools to cut the bung down as you're suggesting.  Another started by Steve Cole discusses specifications, it's a very worth while discussion and may include the ways/tools I mentioned.  You might check his threads.

In my case I needed 45 deg, stainless bungs with the exposure required and ended up having them fabricated.

Evo, I have been reading everything here, and have gotten the depth spec from Steve, as well as have a copy of the Bosch catalog that speaks to the depth and location preference. If I have to make new bung locations I will, but want to try and modify the depth to see if it helps or even takes care of the situation.

If you look at the pics attached, it's amazing to me that the O2 sensors even pick up the exhaust at all, but the bike runs pretty decent, just has some lean spots in lower RPM's. I'm sure that the entire range would be improved with better exhaust sampling from the O2's. I may be able to sunk the sensors another 3/16" that may be pushing it. But it also may put the sensor in the stream enough to read correctly.

I looked at my OEM pipes, the rear is really not that bad, the front is exactly like these are in the picture. I have a spot face tool I use for the tops of valve guides when setting up really high lift cams in Shovels with valve seals. It'll only cut a 0.937" diameter, and I need to cut 1.010" diameter.

I can understand that the higher RPM's are getting a better reading, as you get exhaust back pressure at higher RPM, causing the pocket the O2's are in to get filled, and then can sample. At lower RPM, the exhaust scims on by.


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[HogBag]

Ohio
The bung needs to be on the other side of the pipe about 1/2 inch shorter to let the sensor sit well into the exhaust flow and sample at low revs.
Sorry man but that's the worst location for the sensor on a aftermaket exhaust I've seen. Who's pipe is it ?

[Hilly13]

Ohio
The bung needs to be on the other side of the pipe about 1/2 inch shorter to let the sensor sit well into the exhaust flow and sample at low revs.
Sorry man but that's the worst location for the sensor on a aftermaket exhaust I've seen. Who's pipe is it ?

Aint it just!

[Eleft36]

[ [/quote] 
I can understand that the higher RPM's are getting a better reading, as you get exhaust back pressure at higher RPM, causing the pocket the O2's are in to get filled, and then can sample. At lower RPM, the exhaust scims on by.
[/quote]

I not an engineer or any kind of scientist, but my simple logic tells me that there nothing else in the pipe while the engine is running but exhaust gases.    If not, what is being sampled and how does it get there? Assuming no leaks.


Al

[Ohio HD]

Ohio
The bung needs to be on the other side of the pipe about 1/2 inch shorter to let the sensor sit well into the exhaust flow and sample at low revs.
Sorry man but that's the worst location for the sensor on a aftermaket exhaust I've seen. Who's pipe is it ?

Aren't they awful? This is a D&D Fatcat, if anyone needed a new pipe and wanted to tune it for closed loop, Id 'strongly recommend buying another brand.

Biggest problem isn't picking the best location, it's picking a location where they'll work, and not be sticking outward into the  bike frame or ?. John was kind enough to post his pics of his after relocating them (post #12) , that's about the best that I can see can be done to them.   

http://harleytechtalk.com/htt/index.php/topic,50510.msg530384.html#msg530384

[Ohio HD]

[

I can understand that the higher RPM's are getting a better reading, as you get exhaust back pressure at higher RPM, causing the pocket the O2's are in to get filled, and then can sample. At lower RPM, the exhaust scims on by.
[/quote]

I not an engineer or any kind of scientist, but my simple logic tells me that there nothing else in the pipe while the engine is running but exhaust gases.    If not, what is being sampled and how does it get there? Assuming no leaks.


Al
[/quote]

With any type of gas, when it's traveling through a conduit, if there's a change in direction to the conduit, you get a negative pressure area on the inside radius of the conduit. So you're sampling at less than optimal at that point, if that's where you're trying to read. When the flow rate increases, the negative area decreases some due to back pressure, and your readings will improve.

[wolf_59]

Ohio if that bung is threaded all the way through I would try to trim it to where it just covers the end of the threads of the sensor before installing new bungs.

[Ohio HD]

Ohio if that bung is threaded all the way through I would try to trim it to where it just covers the end of the threads of the sensor before installing new bungs.

Wolf, that's what my thoughts were as well, that's why I was inquiring to see if anyone had any positive results cutting the bung down, in a situation like mine. I can't take it a deep as I would like, simply because I'll end up in the weld on one side, and if I go deeper there, I can't get a socket on the sensor at some point....     

As I had said, I'm truly astounded that it runs this good. But I also remember as soon as I stuck this pipe on, to combat a separate problem with the OEM exhaust, I was having issues. And since this is my first try at tuning FI, I just figured I was doing things way wrong. Guess I didn't do too bad under the conditions. I'm just pissed at myself or not questioning the height and location, I mean it's not like I didn't see them.   

[wolf_59]

I haven't cut any O2 bungs back but have done a few O2 conversions using a 18X1.5 mm half nut, they're about .030 thicker than the threads on the sensor and just thread them on to a plug chuck them up in the little lathe and round the corners off, locate a place to install them on the pipe within the 4-6 in range from the head, drill the pipes and enlongate the hole so the bung sets down in the pipe on the ends and sets on top of the pipe on the sides weld it up

[BVHOG]

Cant find the thread but hardtail made a tool for doing this.

[wurk_truk]

Cant find the thread but hardtail made a tool for doing this.

http://harleytechtalk.com/htt/index.php/topic,38168.0.html

[Ohio HD]

Yep, I have his pics, and am going to order a spot facer large enough if I can't find one today. I have one that'll cut 15/16", I need one inch.





Brian

Sent from my iPhone using Tapatalk


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[Ohio HD]

Cant find the thread but hardtail made a tool for doing this.

http://harleytechtalk.com/htt/index.php/topic,38168.0.html

That's the one.

[Ohio HD]

Well, the rear, which is by far the worst, I can get like I said, maybe 1/8". But D&D gave me only two more threads than the sensor now uses. So shortening them is out, I have to fabricate some 5/16" long bungs, and try to find a spot that isn't going to interfere with the rest of the bike, and doesn't look like total crap.

I had tried to contact D&D, I wanted their take on all this, they're non responsive, so that tells me what they think of their customers when they have an issue. I may try to call next week, I only had time for email this past week. So they won't ever see another dime of my money. And if I can't get this "Potty mouth"ty exhaust the way I want it, I'll move on to something else. My time is worth much more than an exhaust system, and I've already wasted a lot of it trying to get a tune so far.

[hrdtail78]

I have good luck cutting them down.  I have done D&D also.  Somewhere I have posted back to back scan data (generic O2) from a cold start.  It shows the time it takes for the O2 sensor to become active.  Happens a lot faster with trimmed bungs.  Having only one or two threads on the short side doesn't bother me.  You still have plenty of thread engagement on the other side.  Problems that can occure is the exposed thread now gets carbon on it and can make it hard to unthread without working it back and forth.  I don't think the LSU's or other broadband sensors are affected has much, but these are built to read from the end of the sensor. 

I would try trimming.  Really can't hurt.  If it doesn't work.  You are back to cutting them out and welding new ones in.

[N-gin]

I benefitted greatly.
I have the ThunderHeader on my dyna around the original bungs were a bunch of snot left from the welds also the bungs were so tall the tip of the sensor was just barely in the exhaust stream.
I cut my bungs about 3/8 inch and cleared any overhanging welds. I also concaved the area around the O2 using the thickness of the weld and bung area. After that my readings were a lot more consistant.
Before I would go out and do Vtunes and constantly make corrections. The readings were never consistant and always around 8% out with each tune.. After the mod I Vtuned twice and all the eareas were within 1-2% of each other.

[Evo160K]

Ohio HD,
If you want to try to modify your bung in the existing location, before relocating it, would it make sense to use your 0.93" cutter then go back and trim/file off the remaining outer ring?

[Ohio HD]

I have good luck cutting them down.  I have done D&D also.  Somewhere I have posted back to back scan data (generic O2) from a cold start.  It shows the time it takes for the O2 sensor to become active.  Happens a lot faster with trimmed bungs.  Having only one or two threads on the short side doesn't bother me.  You still have plenty of thread engagement on the other side.  Problems that can occure is the exposed thread now gets carbon on it and can make it hard to unthread without working it back and forth.  I don't think the LSU's or other broadband sensors are affected has much, but these are built to read from the end of the sensor. 

I would try trimming.  Really can't hurt.  If it doesn't work.  You are back to cutting them out and welding new ones in.

I was headed down that road, to trim, and if it didn't work, then replace them. But I now think that I'll just replace them. The front O2 location isn't to bad, and if it could be lowered enough, may be fine. The rear, well, it's not going to work well no matter what I've decided. It's right in the inside center of radius, and exhaust gas must almost completely miss it. I think I'll just move them, I made up a couple of new bungs, and with the thickness of the exhaust pipe, these will put the entire sensor into the exhaust stream.

The next time this motor starts, unless I have to delay it, it;ll be a fresh 107 top end. So I want to make sure that it's able to read the exhaust correctly, and I'm able to tune it.



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[Ohio HD]

Ohio HD,
If you want to try to modify your bung in the existing location, before relocating it, would it make sense to use your 0.93" cutter then go back and trim/file off the remaining outer ring?

Well I tell you, great minds think alike. I was thinking the same thing this afternoon, but I've decided to replace them. The rear is in such a bad place, I don't think it'll work out where it is.

[Ohio HD]

I benefitted greatly.
I have the ThunderHeader on my dyna around the original bungs were a bunch of snot left from the welds also the bungs were so tall the tip of the sensor was just barely in the exhaust stream.
I cut my bungs about 3/8 inch and cleared any overhanging welds. I also concaved the area around the O2 using the thickness of the weld and bung area. After that my readings were a lot more consistant.
Before I would go out and do Vtunes and constantly make corrections. The readings were never consistant and always around 8% out with each tune.. After the mod I Vtuned twice and all the eareas were within 1-2% of each other.

Good to hear! I think I'm just going to replace them and be done with it. If I don't, I know me, I'll always wonder could it run better if I replaced them, and used a new location for the sensor....     

[Evo160K]

This "how-to" video from Zipper's may be useful.  It helped me.

Thundermax O2 Sensor Bung Installation