Just curious Roger but are you thinking about adding or inserting a DC bias voltage to skew the narrow band O2 sensor waveform as presented to the Motronic?

Hi Jim, I'm analyzing 10,000 or so narrowband data points that I captured using the GS-911 before I mounted he Wideband O2 sensor. These points give me a good idea of the voltage range of the stock sensor in normal (14.7:1) open loop, closed loop and warm-up operation.

Although theory (and a lot of experience) suggest that there isn't enough useable AFR info at the rich end of of the narrowband curve, www.nightrider.com has a range of products that it (convincingly) claims will shift narrowband O2 sensors to 14.2:1. My experience with the LC-1 says that a lot of the richening benefit to driveability occurs at the 14.2 (lambda = 0.965) level.

What I'm not sure is whether there is any interest in a plug in adapter for the stock sensor. RB

Replacing the stock narrowband O2 sensor with a Wideband O2 Sensor and Controller may be more of a project than many would undertake. The more I've worked with it the more comfortable I've become in saying that it's quite straightforward and without complication. It's also possible though that you could get a modest shift of Lambda with the stock narrowband sensor.

If you go back to page 1 of this thread you will find the chart that I'm reposting below. This is a plot of all the O2 sensor voltages that the GS-911 acquired during an extended test run. It is that known that something in the vicinity of 450 millivolts (0.45 on the chart) corresponds to a Lambda of 1 (meaning an AFR of 14.7:1). What is not so well documented is what is the AFR on an Oilhead when the O2 sensor voltage is between 650 and 900 millivolts. If the AFR is only 1% richer in that range then there's not much that can be done with the Narrowband sensor. However if those voltages correspond to a mixture that is 3-4% richer then there is probably a circuit and set of bias voltages that would allow a slightly richer operation of the Oilhead with the stock O2 sensor.

Since I'm planning to have the LC-1 initiate a recalibration of the Wideband Sensor (another neat thing about the Wideband O2), I'm thinking of putting my Narrowband in temporarily to see what the Motronic will do with a modified sensor. In other words will it hold Closed Loop if I alter the biases and voltages?

If that worked, then I might take my exhaust to a welder and have a second bung added so that I can accurately measure the Stock O2 sensor under standard and modified conditions.

If anyone knows of a good quality welder in the Metrowest Boston area I would gladly take the recommendation.

Stock O2 Sensor

My gosh, I would think in your area good stainless welders would be easy to find. How about the yellow pages under metal fabricator or machine shop?

That helps, so I'm looking for a SS fabricator.

AEM makes a No-Weld O2 Sensor bung that is a clamp with bung and strip of adhesive. I thought about it for a while and decided against it.

There are surprisingly few good spots on the R1150RT to mount a second bung but It looks like the weld-in bung will fit on top of the cat/muffler about a half inch back from the attachment clamp. I found a photo (below) that shows the stock O2 sensor mounted on the inner side of the feed tube to the cat. It appears that there's clearance if I mount the bung on top and near the front.

An advantage of that spot is that it will free-up about a foot of the wideband sensor's cable that is used now to reverse course and clear the transmission. A downside is that I think the sensor would need to be removed before removing the exhaust.

While you're at it you could live dangerously and take your grinder with a thin cut-off wheel and open the top of the cat chamber and cut out that offending piece of crap called the cat converter. Then you would have lots of places to mount a bung.
Of course you would still have to find a stainless welder but think how wonderous it would be to just get rid of that offensive mechanism. Nope, haven't been drinking.

Took the grinder to my '04 when it was but a youngster.

I'm concerned that removing the cat material would alter the balance of the VE (fuel) table by changing the pressure at the exhaust outlet so I'll keep the Cat for the time being.

Here's where I'm thinking of mounting the bung and second sensor. If it works out, it might become the final home for the wideband.

That looks to be a good place and better than stock for sure and you could remove and replace much easier. Might be hard to remove exhaust assembly without first removing the O2 sensor but these are motorcycles not cars so nothing is easy due to compactness.

I don't think the cat converter is at all restrictive so about all you get with removal is a somewhat more mellow exhaust note. I wouldn't be concerned with changing back pressure. As I've said before the reason I opted to remove was the heat directly below the transmission but I really wonder if that's a valid issue. Guess I just had 50 bucks burning a hole in my pocket so I gave it to a welder. Guy did a neat job and you would never guess the catectomy was done. I do wonder how a richer mixture over time would affect free flow through the cat?

I've added a second O2 bung so that I can use the LC-1 Wideband sensor at the same time that the narrowband stock sensor is installed and feeding the Motronic.

The exhaust is back on with the Wideband sensor in the position near the catalytic converter, and the Narrowband sensor mounted in the new bung near the clamp. By connecting the Narrowband sensor to the Motronic and using the LC-1 as a recorder, I'm already getting data on the Narrowband/Motronic combo.

The first things that jump out at me:

—The stock Narrowband sensor is much slower than the Wideband, no question. That means the Motronic takes a lot longer to make corrections.

—The AFR spread is much larger with the Narrowband sensor. The larger spread plus the slower response shows fueling patterns that take seconds to change direction. Even in the quick data I've taken I've seen the mixture take 4 seconds to go from 15.4 to 14.2 while in closed loop. This is a long time and a fairly large change of mixture. The mixture change is large enough and slow enough that I'm sure it could be felt as su----g.

I'm going to do some riding with it tomorrow if the rain holds off and then post some plots and photos.