How is 02 sensor used by computer?

[CordovaJohn]

I understand the 02 sensor measures oxygen content in the catalystic converter. What I don't understand is how the computer uses this information. Does the computer adjust the timing and/or fuel flow dynamically in real time? Does it work more on averages over time? I have heard it selects the map. Is it used to build a map? The learning the computer does after reset - what is that based on?

If someone that understands could give an overview of how all this works (or give links to where it is explained) I would appreicate it. Thanks!

[towerworker]

Where art thou Boxermania?

[macx]

Just real briefly for starters.

Under heavy throttle the computer does not use info from the sensor but reverts to a
factory programmed fuel & timing control map, one of several depending on which
country etc you bought the bike.

The computer just uses sensor info during basically steady state rpm as in cruising.
Also could be thought of as under light load. Within a limited range, it responds to
hi or low oxy readings (versus what it's told it should see) by slightly richening or
leaning the mixture. When heavier throttle is applied (signalled thru the throttle
position sensor which tells the computer how much "load" - or opening of the throttle -
by a varying voltage signal) it reverts to the programmed map.

This is a relatively crude system, basically an "alpha n" system, and is only adaptable
- or better stated self adjusting - within a very narrow range during cruising. It does not
measure the actual amount of air the engine is taking in - or "mass" - which is dependent
on a variety of factors including temperature and humidity as well as cfm of airflow,
and adjust the fuel (and timing) accordingly. So you get pretty much what the engineers
designed into the bike irregardless of varying environmental conditions. They do try to
take all the variables into account during the design and testing process, but of course can
only come within a certain range of accuracy that way.

[boxermania]

towerworker....thanks for the intro.

Short and sweet - Our bikes use a narrow band O2 sensor which is a 1st gen device with limited service in this application. In essence it only works while the engine load is steady state, in other words, when the throttle is held steady for a fixed period of time, like on the highway.

Under the above condition, referred as "close loop operation” the ECU looks at the sensor signal and adjusts the pulse time to the injectors to reduce the amount of fuel injected to a pre-determined value in the interest of maximizing fuel economy, timing is not affected at all.

Once the need for acceleration is required the O2 sensor is out of the picture and a designated fuel map selected by the CCP plug, as there are several maps stored in the ECU to satisfy the different countries emission requirements, in the ECU takes over.

Hope this helps

[AirForceDirt]

So, with no CCP installed, which map is selected?

[Sunbeemer]

I believe without a CCP it defaults to the map for European bikes without the cat.

My question is, does the Motronic use the O2 sensor data to adjust the mixture even when the bike is cold? My bike runs so smoothly while it's still cold, but starts hunting at constant throttle (esp. ~2K-3K rpm in 2nd gear) when warmed up, so I figure that's when it goes into "closed-loop" mode.

[duke]

Where art thou Boxermania?

Waiting for his hug and the promised addition to the spanner guru list I suppose?!!? (see the other recent post RE: Oxygen sensors)



Sorry Boxermania, just could not resist ...

[CordovaJohn]

Thanks for all the info. It sounds like any problems accelerating under full throttle are not caused by the O2. (I assumed) my O2 got a lot of gas dumped on it when oil saturated the left stick coil. Have since replaced the two coils and all is better (for the 3 days I have ridden). In addition to just trying to understand how things work, I was just wondering if the O2 may need replacing, but it sounds like it probably does not. Thanks again.

[boxermania]

Yep....those stick coils are begining to rear their ugly head......I would say that most of the R's out there are at the time in their lives where the stick coils are the common failling component.

[jcridge]

+1 on the stick coils,

Old = 95% of all carburetor problems are ignition related...Lucas
New = 95% of all surging and performance issues are ignition related...BMW

Isn't it amazing after all theses years, we are right back where we started...fire, without it, we not that far removed from the caveman.