2004 R1150RT Wideband O2 Sensors

[Roger 04 RT]

Adding this info from another thread so that Wideband O2 stays up to date.

Below is a chart of a startup sequence and drive off. You can see the richness starting on the left, moving to closed loop at 14.2:1 AFR on the right. In between are some lean splikes from deceleration enleanment and from fuel overrun cuttoff (biggest splikes). You can also see a restart just right of center where it goes quickly through a rich sequence (idle lever not up). You can also see some rich blips as I roll the throttle on.

[Roger 04 RT]

Here is a plot of AFR for my '04 R1150RT cold started with the throttle and cold start levers in three positions. Ambient temperature was 35 F.

1) For the left hand third of the plot, the cold start lever is on, the engine is idling smoothly and the AFR is in the 12s. Notice that the mixture is appearing to get slightly richer in the first 40 seconds. This is because the fuel is being atomized and burned better, leaving less oxygen in the exhaust. Less O2 is interpreted by a wideband oxygen sensor as a richer mixture.

2) In the center part of the chart, the cold start lever is abruptly switched off. At first the mixture seems rich due to less air going in. But after a few cycles, with less air going through the TBs and the engine still cold, the rich mixture isn't atomized as well, the engine misfires, and the O2 sensor reads the un-consumed oxygen as a leaner mixture. I will say that a different way: there was enough fuel but not enough air and all the fuel didn't burn, leaving unburned O2 in the exhaust which was read by the sensor as leaner.

3) Cold start lever still off but throttle cracked open for smooth idle. Better combustion so the AFRs return to the 12s as the fuel and oxygen burn more completely.

Bottom line: cold engines need more fuel AND a bit more air to idle well. The oil temp sensor reading tells the motronic to add fuel, the rider uses the cold start lever to add air.

[jammess]

Hello Roger,
I have a question. What would be the result if one were to simply remove the stock O2 sensor and plug the bung hole, disconnect the two heater leads, and leave the O2 sensor connected and just suspended in open air? Would the sensor send a continuous lean indication to the Motronic which would result in a continuous rich AFR? I mention disconnecting the heater wires because it would be easier to find a place to tie the sensor without risk of cooking something. Would the Motronic think that the O2 sensor has malfunctioned and just revert to maximum lean because it wants to see a continuously changing AFR?

I'm too cheap to invest in a wide band set up and that is mostly because I can buy pure gas so easily. That said I would like to richen the mix a bit but don't want to spend money doing it.

[Roger 04 RT]

Hello Roger,
I have a question. What would be the result if one were to simply remove the stock O2 sensor and plug the bung hole, disconnect the two heater leads, and leave the O2 sensor connected and just suspended in open air? Would the sensor send a continuous lean indication to the Motronic which would result in a continuous rich AFR? I mention disconnecting the heater wires because it would be easier to find a place to tie the sensor without risk of cooking something. Would the Motronic think that the O2 sensor has malfunctioned and just revert to maximum lean because it wants to see a continuously changing AFR?

I'm too cheap to invest in a wide band set up and that is mostly because I can buy pure gas so easily. That said I would like to richen the mix a bit but don't want to spend money doing it.

Without being heated, and in open air, the O2 sensor produces no voltage and looks like an open circuit to the Motronic. The Motronic senses that nothing is connected and uses the fuel table directed by the Coding Plug. So I don't think it would accomplish what you want.

Because Closed Loop operation with the O2 sensor installed allows the Motronic to learn about changes to fueling (injectors & fuel pressure, which can vary several percent), air flow (filter aging) and even battery voltage, I'm not a fan of disconnecting it. Because the Coding Plug tells the Motronic what intake tubes, cams and heads you have, it makes good sense to leave that alone. So the choices for a bit richer for $0 look pretty limited and have been discussed in many other posts.

[jammess]

Without being heated, and in open air, the O2 sensor produces no voltage and looks like an open circuit to the Motronic. The Motronic senses that nothing is connected and uses the fuel table directed by the Coding Plug. So I don't think it would accomplish what you want.

Because Closed Loop operation with the O2 sensor installed allows the Motronic to learn about changes to fueling (injectors & fuel pressure, which can vary several percent), air flow (filter aging) and even battery voltage, I'm not a fan of disconnecting it. Because the Coding Plug tells the Motronic what intake tubes, cams and heads you have, it makes good sense to leave that alone. So the choices for a bit richer for $0 look pretty limited and have been discussed in many other posts.

Well duhhhh...I read up on O2 sensor operation and you are correct. I should have educated myself before that stupid question. I guess there is no good way (cheap) to fool the Motronic unless maybe buy a 555 timer chip and build an O2 simulator but without proper test equipment what would be the point? Answer: No point! I have spent mucho dinero this winter on my motorcycles what with a new (used) final drive for my '81RT and purchasing my brand new '94 R1100RSL then a new fuel pump, fuel filter, strainer, quick fuel line disconnects, clear windscreen, passenger backrest, and luggage rack with mounting kit to accommodate the backrest. My better half is at her limit.

The 555 timer might not even work because maybe the Motronic wants to see a continuous change in O2 sensor output as in the mixture going rich then lean then rich then lean continuously. Not sure how this ECU would react to a continuous lean O2 simulated signal and then with no way to actually measure the resulting air fuel mixture.... I'm done.

Well, almost done. Roger, do you know of anyway that one can easily detect when the Motronic goes closed loop with a dvm? A high/low indication would be great. Also, does the Motronic enter closed loop when fully warmed up and at idle on the center stand? I have been thinking about constructing a 555 timer circuit and subbing it for the O2 sensor but I need a way to detect closed loop. My circuit would cycle at a rate of one alteration per second and be capable of being adjusted from .2v to .9vdc. I would adjust for about .35 volts and go for a ride with new set of plugs then check plug color after 50 miles or so but I need to be able to detect closed loop operation or I think my time would be wasted.

[Roger 04 RT]

...

Well, almost done. *Roger, do you know of anyway that one can easily detect when the Motronic goes closed loop with a dvm? *A high/low indication would be great. *Also, does the Motronic enter closed loop when fully warmed up and at idle on the center stand? *I have been thinking about constructing a 555 timer circuit and subbing it for the O2 sensor ...

The Motronic 2.4 can be read but I don't how the GS-911 does it. The MA 2.4 is closed loop after warm up at idle. Let us know what you come up with.

[Roger 04 RT]

Now that I can program my Closed Loop AFR where I want, I've started to think about the "best" place. I've been running between 13.8 and 14.2:1. I've also been thinking about why such a small mixture shift, only several percent, makes such a big difference to performance and smoothness. Yesterday I came across an article on EGT, CHT, AFR and mixtures that answered many of my questions. Here is a link to that three part aviation article: Understanding Best Power/Economy -- Back to the Future . The article also explains how you might get a "lean" mixture to run smoothly. (Chart from the article below.)

Some key points from the article:
-- In the engines they have studied, cylinder to cylinder AFR variation can reach 8-12%. So at the extreme, one cylinder could be as rich as 13.8:1 and the other as lean as 15.6:1 at the same moment.

-- Rich of Peak EGT (richer than about 14.7:1) operation is much less sensitive to AFR variation due to the depletion of oxygen by combustion. In other words, once the oxygen in the cylinder is used up, a little more or less fuel doesn't effect the horsepower of the cylinder/engine.

-- When operating Lean of Peak (leaner than 14.7:1), difference in fueling leads directly to differences in cylinder/engine power. There is still oxygen available, adding a little fuel adds a bit of power.

-- Roughness in leaned engines is usually due to cylinder to cylinder power imbalances, not lean misfiring.

-- Motors with very well balanced air intakes and fuel injectors can be run Lean of Peak more effectively.

-- Considering cylinder head temperature, 14.7:1 is the hottest AFR.

Some thoughts after reading the article:

-- A shift of AFR to 13.8:1, will add several percent to BHP in the cruising range, but not at high powers where the Motronic already runs richer mixtures. (N.B. CO pot R1100s are specified to idle between 13.8 and 14.1, so I guess the engine is okay operating there.)

-- After balancing airflow at idle, for motorcycles using a stock narrowband O2 sensor, it might be better to adjust the right cylinder throttle plate for smoothness (equal HP) at 3000-4000 RPM, rather than exactly equal manifold pressure. How could that be done?

-- There is value in having a very well matched set of injectors. What is the best shop for getting these?

-- For a stock setup, Open Loop operation will be smoother than Closed Loop since the fueling isn't varied. Adding a BoosterPlug will add power and smoothness when the O2 sensor is disconnected by getting closer to a best power mixture, also adding some insurance against leanness caused by E10 fuel.

-- My LC-1 Wideband O2 sensor will smooth out Closed Loop operation with a shift to 4-6% percent richer than 14.7:1. Example below.

When the R1100/1150 engine goes into closed loop operation, the fueling is ramped a few percent below 14.7:1 and a few percent above. Given the above points, *I can imagine a case as follows:

A) Cylinder left is 5% leaner than Cylinder right
B) Motronic Closed Loop AFR range: +/- 2.5% (est.)
C) Therefore in Closed Loop the left cylinder runs between 14 and 14.7, while the right cylinder runs between 14.7 and 15.4.

Although this is hypothetical, and you could imagine better and worse scenarios, in this case the left cylinder is always Rich of Peak, its power doesn't vary much during the Motronic's Closed Loop operation. But the right cylinder in my example is always Lean of Peak, so as the Motronic ramps fueling up and down, the power in the right cylinder varies. (Sounds like surging.) Even with these imbalances, a shift of 5% to 14:1 Closed Loop AFR will keep Closed Loop operation rich of peak for both cylinders at all times.

Here are some interesting charts from the article:

[Roger 04 RT]

For anyone interested in RT spark timing, here is the ignition plot from a short ride I took in January.

The left axis is degress for dwell and timing, and also degrees C for engine temperature. The right axis is RPM. The data was taken from my GS-911 and is for an '04RT. It looks like I might have made the ride with the Cold Start lever up all the time.

[Roger 04 RT]

Idle dwell at 8 degrees. Even spread for most of the ride between 10 and 40 degrees , max advance is 43. Cold spark timing at 12 degrees advance.

Notice that this spirited twisty ride was mostly under 4000 RPM.

[Roger 04 RT]

For those who are interested in more of the electronic details, some new data.

Yesterday I was able to borrow an oscilloscope for a few hours. It was very interesting to see the raw waveforms being sent by the LC-1 (Innovate Motorsports) to the narrowband input on the Motronic ECU. The persistence of the scope I used wasn't long enough for photos so I'll just attempt to describe what I measured.

As a baseline, if I was examining a functional narrowband sensor during Closed Loop operation, I would see a waveform that simply alternated between 100mV for half a second or so and then 900 mV for half a second or so, in a repeating cycle until the Closed Loop mode ended--usually due to a change of throttle. The Motronic would be creating this alternation by steadily increasing its injector pulse width until the O2 sensor jumped to 900mV. Then in would start slowly decreasing the pulse width until the O2 sensor voltage abruptly fell to 100mV--this is what creates Closed Loop operation. The frequency of this alternation would be about once per second or so. (As an aside, if the fueling table said that the average pulse width for 14.7:1 was, for example, 2.00 mS; but the average pulse width for Closed Loop was 2.08 mS; then the Motronic would "learn" an "adaptation value" of +4% and it would start there next time, it would also add 4% to similar Open Loop fueling. Also, in Closed Loop I might have seen a +/- 3-4% spread between richest and leanest values, for a 6 to 8% swing in fueling.

What I learned by looking at the LC-1 real time waveforms (there are two analog outputs--one for the motronic and one for the gauge) was the following:

1) As I have the LC-1 set up, the Motronic is able to alternate the mixture once per second, just as with the narrowband sensor--this is good, it means the LC-1 solution is compatible with the Motronic.

2) In Closed Loop, the Motronic tries a new step every 30 to 50 mS (50 thousandths of a second).

3) Each Motronic fueling step is about 1%. So if it started at, say, 2.00 mS it next tries 2.02 mS, then 2.04 and so on, same step size on the ramp down.

4) The LC-1 is nearly instantaneous in its response. As a result, I observed a narrow spread of +/- 1% to +/- 2%. The stock narrowband O2 sensor is 2 to 4 times as large because it responds more slowly, which creates a variation that is probably felt as surging.

5) Because the LC-1 is so fast, the 100 mV to 900 mV transition isn't a single jump from one voltage to another, it is a series of 100 or 200 mV steps. The Motronic handles this difference without a problem.

Going back to point 4) has given me the idea that by using an LC-1, I might be able to run without surge or hesitation or weakness at AFRs above the 13.8 to 14.2 that I've tested so far. Next I will try 14.7:1 (stock AFR) and then 15.2:1 to see how those mixtures run. Maybe we can "create" some more gas mileage for those who aren't interested in the power increase that 13.8:1 brings.

I will probably look at this some more next time I borrow a scope.

RB

[Roger 04 RT]

For anyone interested to read about air balancing vs fuel injector balancing vs richer mixtures. The Background on page 7 of this Fuel Injection Patent is interesting reading.

It makes four key points:
--Rough running under lean conditions is caused by power imbalances between cylinders
--Air Imbalance is not the main cause of these power imbalances
--Fuel injector differences directly result in power imbalances.
--Fuel injector imbalances can be solved by carefully matching injectors, or by running mixtures richer than stoichiometric (14.7:1 AFR)

The Wideband O2 project has taken the richer mixtures route so far. Although I'm considering getting a matched set of injectors and seeing how much the AFR can be pushed in the lean direction.

[Roger 04 RT]

I know that a few of you have wondered what fuel mileage would be at the richer 13.8:1 AFR I'm running.

Just ran my first gas mileage test using the LC-1 Wideband O2. All the driving was on local trips, no highway, up to 25 miles per trip, some as short as 5 miles, plenty of lights.

I burned 2.48 gallons, for 106 miles. That's 42.7 MPG, give or take.

I still plan to take a highway trip and see what the mileage is.

[happy wanderer]

I know that a few of you have wondered what fuel mileage would be at the richer 13.8:1 AFR I'm running.

Just ran my first gas mileage test using the LC-1 Wideband O2. All the driving was on local trips, no highway, up to 25 miles per trip, some as short as 5 miles, plenty of lights.

I burned 2.48 gallons, for 106 miles. That's 42.7 MPG, give or take.

I still plan to take a highway trip and see what the mileage is.

That is pretty darn good for in town riding. It should be quite a bit better humming down the highway.

[Roger 04 RT]

I've been running with an LC-1 and BoosterPlug, kind of a belt and suspenders approach. The LC-1 for Closed Loop and the BoosterPlug for Open Loop. For some time I have wanted to see how the LC-1 and Motronic performed without the BP shifting the stock Open Loop AFR tables 6% richer because I know that on the 1150RT Adaptation Values get built from Closed Loop and get applied to Open Loop. Confirming it worked that way would mean that the BoosterPlug was a nice-to-have (since I own one) in my application, not a need-to-have.

A key to these tests is a cold start, watching how the Motronic and LC-1 transition from cold (enriched and Open Loop) to warm (no afterstart or warmup enrichments, and Closed Loop). Therefore both tests were begun immediately after start and on the same course. (Note: In the upper chart, second half, I was modulating the throttle more than in the second half of the bottom chart. Otherwise, they are for the same course.)

I got out for the first two of several rides. In the attached photo, you can see the first ride (top chart) after the Motronic is reset with no BP, and then a day later, the second ride. In the first ride after reset (in my theory, before the Adaptation Values referred to in the BMW Service manual can be rebuilt) you can see a lot of deviations from 13.8:1. If you look carefully on the left of the top chart you can see the mixture starting at about 12:1 and then watch what happens while the bike warms up at about the 3 minute mark (same point below). You can also see the histogram on the right, it being the distribution of all AFRs during the ride.

In the below chart, second ride from a cold start, you can see better adherence to 13.8 and a tighter histogram. (Ignore the spikes that go to the top of the chart, they are Overrun Fuel Cutoff.) It also gets to 13.8 right away, before the bike has warmed up and before it can be in Closed Loop, in the first minute or so. (Notice the dips to lower AFRs, that's where I'm shifting!) The only surprise in the lower chart is the blip to 14.7:1 (Open Loop target AFR of the reset Motronic) between 1:40 and 3:20 minutes. This was after a stop sign and reacceleration, before CL had started and perhaps (my deduction) in an area of the Adaptation Values table that had not built sufficient data yet.

I plan to make many more rides and watch this closely and will have some more data over the coming weeks.
RB

In the photo, there are two horizonal dotted lines. The top line is 14.7:1 (Open Loop Table before Adaptation) and the bottom line is at 13.8:1 (My AFR target set by the LC-1).

[wjg4oh]

Roger, I really appreciate your generosity in sharing your data on the forum. It sheds a lot of light on an area about which there is much conflicting information. Your data and explanations are clear enough that even a non-technical person like me can follow along, and understand and evaluate for myself what you are doing and what the results are. Very nice!

I've been trying out some of your ideas on my own 2001 R1150GS. First, I found the bike performed better (more power, no evidence of surge) during the first couple of minutes after a cold start when the Motronic is running a more enriched mixture and before it goes to Closed Loop. Then, as you suggested, I disconnected the O2 so the motor would run Open Loop all the time and installed the Booster Plug (thanks for the loan) to enrichen the Open Loop tables in the Motronic. The bike ran beautifully! The surging was gone, throttle roll-on and roll-off were smoother, and the bike ran stronger in the mid-range. (I ran all of these tests with the Cat Code Plug in.)

Yesterday when I was out I decided to do a comparison just to refresh my memory -- I removed the BP, left the O2 disconnected, and reset the Motronic. The surge returned and as near as I could tell the mid-range wasn't as strong, and the throttle on/off was more abrupt. If I'm understanding this correctly, the bike was back at the 14.7 AFR programmed into the Motronic Open Loop tables, confirming that the engine runs better with a richer mixture as provided by the Booster Plug when running Open Loop. I couldn't really tell any difference between Open Loop without Booster Plug, and stock Closed Loop configuration.

If I'm understanding your latest post correctly, it just might be possible that if/when I install an LC-1 on my bike the Motronic might be able adapt the Open Loop tables to function at the same target AFR as the wideband O2 is set at and, if so, could save me the cost of a BP. I'm looking forward to seeing more of your test data with the LC-1 without the Booster Plug to see if you can get the same level of performance as running Open Loop with the Booster Plug. If so, it seems I would have two options -- disconnect O2 and install Booster Plug, or install LC-1.

Keep up the great work, Roger.