O2 sensor eliminator — why?

[Guth_imp]

Or more to the point, why do only some CB1100s exhibit poor fueling characteristics?

I was aware of the issue whenever I would ride my CB but let it slide. However, whenever I would ride my Hawk GT with its old school carbs I was quickly reminded of just how poor the fueling on the CB1100 really was. After bypassing the O2 sensor, there is no perceivable difference between the two in smoothness when running at a steady speed in the lower RPM range.

By the way, my experience seems to be independent of whether I was running the stock exhaust can or the Staintune.

Why the need? Primarily fuel control. The CB's computer (powertrain control module (PCM)) is programmed at the factory to deliver the proper air/fuel ratio for the operating conditions. This is the programming. Programming assumes everything is in proper operating condition. As the CB ages, things go askew. Garbage in results in garbage out. The CB no longer delivers the proper air/fuel ratio for the operating conditions. This is where the oxygen sensor (O2S/HO2S) comes into play. The HO2S is calibrated for the air/fuel ratio of the engine it's designed for - generiocally - 14.7:1 (stoichiometry/lambda). Median HO2S voltage - generically speaking - 450mV equates to 14.7:1. As defects appear they affect the HO2S' median voltage. The PCM will deviate from the programmed fuel injector on-time to compensate bringing the HO2S back to it's designated median voltage in turn bringing the air/fuel mixture back to it's designed ratio.


Let's say the fuel pump weakens and fuel pressure drops. This will result in a biased lean air/fuel ratio. A leaner than desired air/fuel ratio will skew the median HO2S voltage low. The PCM responds to a low median HO2S voltage by increasing the fuel injector on-time from it's original programming. Adaptive fuel strategy, integrator/block-learn, short-term/long-term fuel trim. This is what makes modern vehicles so great. Why folks feel the need to screw this up by removing the HO2S is beyond me.

The PCM is supposed to monitor HO2S performance and illuminate the malfunction indicator light (MIL, check engine) when there's a problem. This doesn't always happen. Japanese manufacturers are hesitant to turn on warning lights. Warning lights upset customers.

HO2S' can be tested using a digital storage oscilloscope (DSO). Artificially manipulate the a/f ratio full rich (propane) and measure maximum HO2S voltage. Artificially manipulate the a/f ratio full lean (vacuum leak) and measure minimum HO2S voltage. Snap the accelerator engaging acceleration enrichment and measure how long it takes the HO2S to transition from lean to rich. Min, max, rate of change. Minimum spec is 0-170mV. Maximum spec is 800-1000mV. Rate of change (170mV - 800mV) should be less than 100mS.

TMI

I'm guessing that your bike is running just fine. My bike on the other hand had become increasingly unsatisfactory as I described in the original post. I was the one having to adapt to changes, not the bike, lol. This lead to my experiment of installing the O2 sensor eliminator. It was cheaper than taking a chance on a new O2 sensor and more than likely less expensive than having the existing O2 sensor tested.

[avsbezzy_imp]

Why the need? Primarily fuel control. The CB's computer (powertrain control module (PCM)) is programmed at the factory to deliver the proper air/fuel ratio for the operating conditions. This is the programming. Programming assumes everything is in proper operating condition. As the CB ages, things go askew. Garbage in results in garbage out. The CB no longer delivers the proper air/fuel ratio for the operating conditions. This is where the oxygen sensor (O2S/HO2S) comes into play. The HO2S is calibrated for the air/fuel ratio of the engine it's designed for - generiocally - 14.7:1 (stoichiometry/lambda). Median HO2S voltage - generically speaking - 450mV equates to 14.7:1. As defects appear they affect the HO2S' median voltage. The PCM will deviate from the programmed fuel injector on-time to compensate bringing the HO2S back to it's designated median voltage in turn bringing the air/fuel mixture back to it's designed ratio.


Let's say the fuel pump weakens and fuel pressure drops. This will result in a biased lean air/fuel ratio. A leaner than desired air/fuel ratio will skew the median HO2S voltage low. The PCM responds to a low median HO2S voltage by increasing the fuel injector on-time from it's original programming. Adaptive fuel strategy, integrator/block-learn, short-term/long-term fuel trim. This is what makes modern vehicles so great. Why folks feel the need to screw this up by removing the HO2S is beyond me.

The PCM is supposed to monitor HO2S performance and illuminate the malfunction indicator light (MIL, check engine) when there's a problem. This doesn't always happen. Japanese manufacturers are hesitant to turn on warning lights. Warning lights upset customers.

HO2S' can be tested using a digital storage oscilloscope (DSO). Artificially manipulate the a/f ratio full rich (propane) and measure maximum HO2S voltage. Artificially manipulate the a/f ratio full lean (vacuum leak) and measure minimum HO2S voltage. Snap the accelerator engaging acceleration enrichment and measure how long it takes the HO2S to transition from lean to rich. Min, max, rate of change. Minimum spec is 0-170mV. Maximum spec is 800-1000mV. Rate of change (170mV - 800mV) should be less than 100mS.

TMI

Great educated answers. thanks for sharing!

[mininsx_imp]

It turns out that I've been doing a bit of lurking here on the forum. Reading with interest the posts of others who have installed an O2 sensor eliminator. The reason for this? My CB1100 had been exhibiting fairly poor fueling characteristics at levels below approximately 3000 RPM. Each ride would end the same way: with me cruising down the street all herky jerky 'til I pulled into the driveway and shut it down. Now to be fair, while this feels like a big deal to me when I'm on the bike, I have no idea whether or not someone watching me pass by would notice this at all (or whether or not they could hear the throttle hunting in my exhaust for that matter).

At any rate, I recently went ahead and ordered an O2 sensor eliminator. Got it installed in just a few minutes. Took the bike for a quick spin around the neighborhood, just putting along nice and slow. It was like night and day. The fueling was incredibly smooth. Next I'll need to get the bike nice and warmed up and see if that makes a difference. I'm hoping that the fueling will remain smooth and steady. That's all I'm really interested in. I'm not concerned about performance gains. I'm hoping that I don't see a decrease in gas mileage.

But my question is this: why the need for this small contraption? It would seem that most here are happy with the fueling on their CBs, some reporting that it's close to perfect. Some report otherwise, a few of which have turned to solutions like the eliminator unit. Could this indicate that some of us have had O2 sensors go bad (or seriously fouled)? I'd be curious to see how my bike would respone to a replacement sensor. However that would be a far more involved not to mention a much more expensive test than just installing an eliminator plug. I guess you could say that my curiosity has only been partially satisfied.

What think ye knowledgeable forum members?

I've got the same problem you have, the low RPM performance is all herky-jerky and definitely not smooth. It reminds me of how my old '74 VW ran with ethanol in the gasoline. Keep us posted on your results because I'm interested if this might be a solution to our problem. Oh, and how about a link to the one you bought?

[Gumby 1100_imp]

Mininsx,

Did you try the TPS reset procedure first? It seems to work for me and many others to smooth out low speed throttle response.
In case the procedure stops working for me, I purchased a Sensor Eliminator from Redline Superbikes in England:

[url=http://www.ebay.ca/itm/o2-Oxygen-Lambda-Sensor-Eliminator-For-HONDA-CB-1100-2013-2014-/321554121939?pt=LH_DefaultDomain_3&hash=item4ade1e84d3&vxp=mtr]http://www.ebay.ca/itm/o2-Oxygen-Lambda-...d3&vxp=mtr

Or this model which includes a screw and washer to replace the Lambda Sensor in the exhaust:

[url=http://www.ebay.ca/itm/o2-Oxygen-Lambda-Sensor-Eliminator-Set-Blanking-Plug-HONDA-CB-1100-2013-2014-/221639679815?pt=LH_DefaultDomain_3&hash=item339ac11f47&vxp=mtr]http://www.ebay.ca/itm/o2-Oxygen-Lambda-...47&vxp=mtr

[Lord Popgun]

Ack gave me one that just plugged into the connector, but I gave it to Ridem. Ack could tell you where he got it, but you may have to PM him.

[Xyzzy_imp]

How much does your mileage go down with the eliminator?

Side note: Have you ever checked out how many hoses there are in the PAIR system? I took the PAIR crap out of my VTX1800 and the fuelling was much better afterwards. There were special machined plates I bought to block the ports.

[Lord Popgun]

In case Xyzzy is asking me, I should have stated I never used it, just gave it away. Others will have to answer him.

[Chapomis_imp]

Guth, it seems yours got progressively worse, whereas my DLX has been that way since mile 1.

Has anyone tried to put the eliminator on a DLX ?

I think it may need 2. When I added 1 the fueling did not change, but the speedo stopped working.

dUh, do you still have spare ones ?

[Gumby 1100_imp]

Guth, it seems yours got progressively worse, whereas my DLX has been that way since mile 1.

Has anyone tried to put the eliminator on a DLX ?

I think it may need 2. When I added 1 the fueling did not change, but the speedo stopped working.

dUh, do you still have spare ones ?

It is a pretty safe bet that the DLX (Deluxe) will need TWO Sensor Eliminators as there are TWO O2 Lambda Sensors. I understand that there may also be a speed sensor plug behind the right side cover that looks very similar to the O2 Sensor Plugs. If the Eliminator was put in the speed sensor plug it would definitely affect your Speedo.

The Eliminators are available in pairs for many bikes that require 2 of them. However, it would seem that the vendors do not yet have a kit prepared for the 2014 DLX containing two Eliminators.

[Motogeezer1949_imp]

When I put the full Yosh on the DLX, I used the right side sensor in the pipe. Used an eliminator for the left side harness connection. Runs fine, no issues, no gas mileage change.