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[porthole]

In the process of changing a tire, decide to change the swing arm bearings, that means pulling all kinds of extra stuff off, especially the 2 into 1 D&D Fat Cats.

The front exhaust valve is nearly white, the O2 sensor is black
The rear exhaust valve is black and the O2 sensor is a light tan.

The bike is running a Revolution Performance Precision EMS.

Ideas as to why the colors would be opposites?

Ideas as to why the front cylinder would be much leaner then the rear on a O2 processed engine?


Front exhaust

[porthole]

Rear exhaust

[porthole]

O2 sensors

[porthole]

O2 sensors

[glens]

No answers, just an observation.  It looks like the rear cylinder sensor is well-bathed in the exhaust stream while the front sensor has only the very tip exposed to good flow.  No doubt if the sensor ain't getting a good sample then its ability to offer quality input is going to be limited.  I don't know if the sensor could be let into the exhaust a little by reaming the bung down and have that be sufficient or not.  It might be as far into the pipe as physically possible but the bung is not located in a good place to begin with.  Think of how a winding stream lets sediment deposit on the inside of the curves...

[HOGMIKE]

In the process of changing a tire, decide to change the swing arm bearings, that means pulling all kinds of extra stuff off, especially the 2 into 1 D&D Fat Cats.

The front exhaust valve is nearly white, the O2 sensor is black
The rear exhaust valve is black and the O2 sensor is a light tan.

The bike is running a Revolution Performance Precision EMS.

Ideas as to why the colors would be opposites?

Ideas as to why the front cylinder would be much leaner then the rear on a O2 processed engine?


Front exhaust

Nice pictures.......can you post some pictures of your plugs?
I agree, something to be concerned about, you would think BOTH cylinders would look similar, not what you see there!
 

[porthole]

Sensors do not need to be "bathed" in a good stream. If the pipe is full of gas and heated to the proper temp, the sensors work.
O2 sensors work like a mini fuel cell, outputting a voltage based on a oxygen content difference between the exhaust and a reference (air).

The bungs on the pipes are both the same depths, the rear exhaust bung is located about 2" further downstream.

Something I just noticed is that the ceramic coating on the pipes is two different shades

[porthole]

Nice pictures.......can you post some pictures of your plugs?

Yeah later today. have to go back to the dealer this morning because the rep did not put two of everything in the bag 

[Steve Cole]

Sensors do not need to be "bathed" in a good stream. If the pipe is full of gas and heated to the proper temp, the sensors work.
O2 sensors work like a mini fuel cell, outputting a voltage based on a oxygen content difference between the exhaust and a reference (air).

The bungs on the pipes are both the same depths, the rear exhaust bung is located about 2" further downstream.

Something I just noticed is that the ceramic coating on the pipes is two different shades

I'm not sure who gave you the above information but it is not correct. At low engine speeds the exhaust comes in pulses and after the main pulse of exhaust travels down the pipe all kinds of things are happening. Have poor sensor position will and does cause just exactly what you are showing. Here is a link to a Bosch catalog that will explain how sensors are to be positions in the exhaust and those sensor you have are made by Bosch so I would follow there recommendations it you want it to work correctly.

http://www.bosch.com.au/content/language1/downloads/Oxgen_Sensor__Cat_WEB.pdf

Go to page D4 and D5 to see how to make the bungs and properly mount your sensors. D4 lower left diagram shows proper installation into the pipe and D5 shows how to make the bung along with proper mounting procedures.

[porthole]

So by that I am to assume that D&D does not know where to correctly locate the bungs?

[glens]

O2 sensors work like a mini fuel cell, outputting a voltage based on a oxygen content difference between the exhaust and a reference (air).

I agree it acts like a power cell, producing electricity due to oxygen level difference across the element, but I'd not say fuel cell.  It really is closer to a simple chemical "battery".

Your sensors' complete systems not only put out signals based on oxygen content differential, but pressure differential as well.  The document referenced earlier may go into that, but the sensor's own closed-loop controllers cause somewhat of a pressure differential as needed (either direction) to get the cell itself to stay at the equivalent of "stoich" engine fuel burn, and the controllers put out their signal based on what it took to create that condition.   Your sensor systems don't measure the pressures, so it's possible the output is just a WAG at times if other than a "hard-coded" pressure differential actually exists.

Does D&D know how to "do" lambda probe bungs?  I don't know.  If you're using one of their complete systems, gasket to muffler tail, unmodified, then by your photos I'd say perhaps they don't.  If all they did was emulate a stock headpipe's bungs but didn't emulate the amount of backpressure in the system then that may be the problem.  To get yours to work correctly the mounting may have to be a bit more unsightly.

An additional possibility may be that you're using -'09 bung locations with an ECM programmed for '10- locations, with the time in the cycle for the sensor poll being too late and the main mass of gas already beyond the sensors.  But that's just a WAG on my part.  Some of the ECM's sensor poll timings are pretty critical, like the MAP.  I don't know about the O2 sensors but imagine that'd be pretty critical too, especially at the lower engine speeds.

Is that front sensor mounted in a location that makes for an eddie?  Exhaust gas will follow the outside of a curve as much as possible, just like water does.

[Steve Cole]

So by that I am to assume that D&D does not know where to correctly locate the bungs?

For the most part all the exhaust guys have not been installing the O2 sensor bungs properly and it does cause issues. This has been going on for years and I've been told by more than one manufacture they do not care. They want to keep from blocking the exhaust flow. Just understand that what your seeing is a perfect case of poor O2 placement. If you look at the 2012 release from HD even they said they were moved for better load speed response and you have to work with it as a system not just mount an O2 and call it good. Many tuners have been turning OFF the O2's simply because they could not understand the problem or know how to fix it.

[uscanuck]

For the most part all the exhaust guys have not been installing the O2 sensor bungs properly and it does cause issues. This has been going on for years and I've been told by more than one manufacture they do not care. They want to keep from blocking the exhaust flow. Just understand that what your seeing is a perfect case of poor O2 placement. If you look at the 2012 release from HD even they said they were moved for better load speed response and you have to work with it as a system not just mount an O2 and call it good. Many tuners have been turning OFF the O2's simply because they could not understand the problem or know how to fix it.

If you don't have the capability to modify the bung depth or location, at least in the short term, would you be better to program the bike to run in open loop until you can get it corrected?

[Steve Cole]

If the O2 sensors are not working correctly you only have a couple of choices. Fix the issue or turn them off. Once OFF you loose the ability for the system to do any correcting for variations in fuel quality that we see these days. This is NOT an issue that is caused by the O2 sensor yet an issue cause by the improper mounting of them and hoping they will work.

[Twolanerider]

Duane, strictly in the FWIW department Fatcats are on all three bikes here.  All with systems that use that same Bosch sensor (EMS on the SEEG and SERK and the T-Max Marelli conversion on the old SERG).  My plugs all look even.  On the SERG and the SEEG have had occasion to actually see the valves and sensors while doing other things after they'd been in servicve for many miles.  They too are even or very very close to it.