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Introduction and O2 Question


roger 04 rt

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roger 04 rt
Roger... looke like a fellow 550 Gami guy...Maybe we could start a Mike Busch lean of peak vs rich discussion :)

 

Good article, isn't it?

 

No argument here ... I don't think that these bikes like being lean and having their fuel ramped when they are. I might match the injectors and run lean if there was no O2 sensor. But since rhe fueling varies in closed loop operation, I think I'll just keep running on the rich side where there is much less sensitivity to fuel imbalance.

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Morning

 

Injector spray quantity is effected by commanded length of pulse, current (voltage) at the injector pintel lift coil, any resistance in the injector driver ground path, fuel pressure at each injector, resistance to flow at the injector spray nozzle, & a bit by temperature of the injector.

 

Even if all is matched per above that still doesn't mean matched fueling as spray pattern of each injector comes into play due to fine atomization of the fuel & how it mixes with the intake air as well as how the air flows past the partially closed throttle plate.

 

The BMW 1100 Ma 2.2 & 1150 Ma 2.4 system uses an injector spray initiated at bottom of piston stroke on each & every revolution. And if the tuning chart I have is accurate the 2.4 also uses an injector spray at TDC for cold starting enrichment (at least that seems to be available in the Ma 2.4 box)

 

The one (or 2) spray per each revolution is about all that is available on the 2.2 & 2.4 box as neither have a camshaft sensor input. Without a cam input or other 1/2 engine speed input no good (reliable) way for the Motronic to tell intake stroke from exhaust stroke.

Same with the lost spark ignition system. Without a cam sensor no reliable way to tell intake stroke from exhaust stroke so it gets one-spark-per-rev as the only input is sees is crankshaft position with no stroke definition.

 

The BMW 1200 with the BMS-K not only uses a cam sensor but uses a separate 02 sensor for each cylinder & the crankshaft input is more precise as it uses an inductive sensor with multi pulse inputs rather than the very primitive hall effect TDC/BDC (only) input of the Motronic Ma 2.2 or Ma 2.4.

 

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roger 04 rt

 

My write-up has lots of details about cleaning.  ...

 

Hey, I wonder how many riders out there are complaining about surging when their problem is dirty injectors cutting the fuel supply? ...

 

But I think the RC (Russ Collins) matched injectors are the way to go.

 

...

 

I was astonished to learn BMW uses a wasted spritz (analogous to the "wasted spark" design), flushing both injectors even at the perfectly wrong moment for one of them. ... 

 

Hi Ben,

I think the answer is some are having surging due to injectors. It's easy to measure valves and manifold pressure, but hard to measure injector performance--no easy way to do it at home--okay, I can think of some crude ways but for $25 per injector, I'll send them out.

 

I read your good injector write up and have looked at the RC site, thank you.

 

BTW, if memory serves me correctly, my 300HP FI aircraft engine has an even simpler injector control. So even if sequential time injection is best, I'm not sure that lack of it's at the route of the boxer's driveability problems.

RB

Edited by roger 04 rt
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roger 04 rt
...

 

Even if all is matched per above that still doesn't mean matched fueling as spray pattern of each injector comes into play due to fine atomization of the fuel & how it mixes with the intake air as well as how the air flows past the partially closed throttle plate.

 

...

 

 

Morning DR,

Lots of great detail there. So let's say I get the injectors and manifold balance close ...

 

Then, if one runs at lambda<1, with all the O2 (okay, most all) consumed by combustion, then I'm not so sensitive to injector variation (even if I add or subtract a little fuel, there's no O2 left to burn it). That means that I can fine tune power by tweaking the throttle adjuster to smooth the engine, relying on my hands, ears and butt.

 

Then, once adjusted, running in the lambda<1 (say 13.8 where the CO pot bikes run!), the power will be less sensitive to the Motronic Closed Loop fueling ramp. The better I match power the closer I can raise the AFR (lambda, sorry to keep switching between them) toward 14.7 and still stay smooth. That said, I like the feel of the 13.8 I've been running the last couple weeks compared to the 14.2, which was itself a big improvement.

RB

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Morning Roger

 

Even with the injectors performing as close as possible & all else in the fueling & ignition system as well as compression & valve timing being as even as possible you still have individual combustion chambers that can be a bit different, as well as intake tracts not being perfectly even, & for sure the exhaust flows different side to side just based on it's design of one side flowing into the other. That probably means a bit uneven back pressure & the reversion would definitely be different. If one cylinder has more residual exhaust in it than the other that will definitely effect the next ignition cycle.

 

Your approach of using something like the LC-1 then setting the entire mixture to a much easier to ignite & better flame propagation is probably the best way to go. As you have mentioned many times a richer mixture covers up a lot of combustion issues.

 

On your single 02 sensor set up you might be able to install separate 02 sensor bungs up closer to the exhaust valves then add a couple of wide bands there & monitor the exhaust 02 content on each side for comparison.

 

Your twin spark 1150 isn't too bad as far as runability & surging goes but I have yet to ride an 1150 single spark that is operating in closed loop that doesn't demonstrate some light throttle surging (not a one so far).

 

Some riders claim no surging in their 1150 single spark but when I ride that same bike I can easily induce surging. Some are definitely worse than others but that could be due to type of fuel used, to tuning issues, to carbon build-up on the valves or ports, to exhaust pipe flow differences, to variances in the combustion chambers or squish heights, to injector flow differences, to TB flow differences, to a multitude of other single or combined possibilities.

 

 

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roger 04 rt
...

 

Your twin spark 1150 isn't too bad as far as runability & surging goes but I have yet to ride an 1150 single spark that is operating in closed loop that doesn't demonstrate some light throttle surging (not a one so far).

 

Some riders claim no surging in their 1150 single spark but when I ride that same bike  I can   easily induce surging. Some are definitely worse than others but that could be due to type of fuel used, to tuning issues, to carbon build-up on the valves or ports, to exhaust pipe flow differences, to  variances in the combustion chambers or squish heights, to injector flow differences, to TB flow differences, to  a multitude of other single or combined  possibilities. 

 

 

 

On my particular 1150, I mentioned at the start of this thread that it was just not a "comfortable" bike in the 3000-4000 RPM range--no surging, just this vague feeling that it wanted the mixture richened, like my plane when it was over-leaned. This was especially noticeable when accelerating through the gears on a spirited, but normal ride. Just reducing the AFR to 14.4 (my first try) took that away.

 

I read a lot of posts on this site and others where riders comment that the R1150 likes "higher" RPMs, above 4000. Some even suggest that riding in the 2500 to 3500 is "lugging" the engine--perhaps true with the stock sensor, but not at all true with a mixture more to the Boxer's liking.

 

Back to your point about twin versus single spark, and my link to the GAMI injector article several posts back. The planes I flew all had dual magnetos and two spark plugs per cylinder for redundancy. Part of the run-up checklist is a mid-power test of the magnetos--run with both, then on left only, then on right only. It is amazing how much the power dips on one set of spark plugs.

 

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roger 04 rt

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.

 

ignition.jpg

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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.

 

Edited by roger 04 rt
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Peter Parts
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.

 

Maybe you should try a hotter plug.

B.

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roger 04 rt

Here is an example of two side by side, horizontally opposed engines running different fuel mixtures. Power Shot

 

One engine is running at Best Power and one is running at Best Economy. Stoichiometric mixtures (the point where are BMW Boxer engines run at cruise) are in between--a little closer to Best Power but let's not quibble, and lets work with Stoic is halfway between the two.

 

In the example of the article, two engines are running side by side on a twin engine, aircraft so the operating conditions are the same. For the exact same power, the Best Power engine is using 20% more fuel than the Best Economy engine! Pretty impressive but our engines won't run there as configured. But it let's us see that for the same power output, a Best Power engine would use about 10% more fuel than a Stoic engine.

 

Since it is power that produces any given speed, in a side by side case, if you add 10% more fuel you get 10% worse mileage, based on this aviation example.

 

In my case at 13.8, I am injecting 6% more fuel; and at 14.2 I'm adding 4% more. I know there are many other factors that can be considered but if I add 4% more fuel, I can get no worse than 4% less mileage (since I am still much leaner than the Best Power mixture in the low to mid 13s).

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Actually the operating conditions are not the same. These are turbocharged engines, and the left engine is running with more boost (higher manifold pressure). Higher boost increases efficiency, hence less fuel consumption for the same power.

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roger 04 rt
Actually the operating conditions are not the same. These are turbocharged engines, and the left engine is running with more boost (higher manifold pressure). Higher boost increases efficiency, hence less fuel consumption for the same power.

 

You are absolutely correct. The point is that they are operating at the same power but different fueling. I want to show that even the wide spread of best power to best economy is only 20% and that Best power to stoic is about 10%.

 

From other threads there is some concern that a few percent richer mixture could lead to 33% higher fuel consumption, which isn't possible in the operating range under discussion.

Edited by roger 04 rt
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roger 04 rt

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

Edited by roger 04 rt
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Peter Parts

You mention something in passing that I believe can settle a difference of opinion I've been having with certain important people for years.

 

I've been saying we ride mostly open loop since each time we budge the throttle, it ends closed loop operations.

 

No dispute about that. You mention that.

 

Unless you ride encumbered by a throttle lock or ThrottleMeister gizmo that inhibits free operation of the throttle, we trim and nudge the throttle maybe half a dozen times a minute (twice that for me, by actual count, even on dull roads).

 

But now you are able to report how big were your throttle nudges that were big enough to return the ECU to the map??????

 

Ben

 

 

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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.

This is exactly what I noticed while experimenting with a PCIIIUSB (wideband) Power Commander with my 1100. The stock calibration may be good for the cat but it is way too lean for best performance, or even a good compromise. Running at 13.8 shows a marked improvement along with a small hit in fuel mileage. It was a while ago since I last went on an experimentation binge but where I have it set now is 14.2 closed-loop with some additional richening in the open-loop map at the common 'surge' engine speed/throttle position range. An improvement in fueling can transform the oilheads but I've never been a fan of the Techlusion due to it's inability to do anything with closed-loop operation and general lack of control (or lack of precise feedback.) The PCIIIUSB is a great unit but pricey. What you're doing here is interesting.

 

Hi Dirtrider - I'm confused by the comment 'You can add a wide band to the Power Commander but it doesn't use the wide band to fuel to, it just uses the wide band as a input device to initially learn from.' The wideband Power Commander does indeed fuel from the wideband sensor output. It connects between the Motronic and the injectors/TPS and takes over closed-loop fueling from the Motronic (and adds/subtracts from the open-loop map if desired.) But I may be misunderstanding what you meant.

 

 

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roger 04 rt

Hi sMiller,

As you can see I've tried a few different mixes too. I found that 14.2 worked very well. Lately I've been running on 13.8. At that afr I really like the low rpm pull of the engine. I just went out for a ride on a nice morning here in the Boston area.

 

Riding along a winding local road at 40 mph, 5th gear, 2500 rpm. I crank the throttle open a quarter or third turn. The bike literally leaps forward, no lugging, plenty in reserve. For reference I weigh a couple hundred pounds.

 

The stock bike under those conditions is running stoichiometric Closed Loop. That means, in theory, all the fuel and all the O2 has been burned. You quickly open the throttle and the Motronic takes a while to catch up. There is no unburned fuel in the mix and the bike lags.

 

Running at 13.8:1, there is unburned fuel (about 6%) so when you open the throttle the added air interacts with the unburned fuel that would have gone out the exhaust and produces more power. Then the Motronic catches up. The richer mixtures are in effect a small accelerator pump function.

 

At least that's my thought at the moment.

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roger 04 rt
You mention something in passing that I believe can settle a difference of opinion I've been having with certain important people for years.

 

I've been saying we ride mostly open loop since each time we budge the throttle, it ends closed loop operations.

 

No dispute about that. You mention that.

 

Unless you ride encumbered by a throttle lock or ThrottleMeister gizmo that inhibits free operation of the throttle, we trim and nudge the throttle maybe half a dozen times a minute (twice that for me, by actual count, even on dull roads).

 

But now you are able to report how big were your throttle nudges that were big enough to return the ECU to the map??????

 

Ben

 

 

Hi Ben,

When I get some time I will take a look at how big the TPS deviation needs to be.

 

What I can tell you from earlier in the thread is that during spirited around town rides the bike is in Closed Loop about 45% of the time, and if it drops out due to TPS input, it gets back to closed loop quickly. Highway rides freehand are around 55% closed loop.

 

Also earlier in this thread you can see plots where the bike rpm is accelerating and the TPS slows down moving and it jumps back into the closed loop program. This was a real surprise.

 

So I would say use 50% as a good rough number.

 

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roger 04 rt

Ben. Have a look at this chart. Rpm, TPS, lambda. Look at how much TPS is varying in the right hand half of the chart and then see how well lambda (closed loop) stays on.

 

datastream.jpg

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Peter Parts

I have to confess that I don't understand that chart and hope you can take a moment to help me with some baby-steps.

 

Is it a a time series running from left to right? If that's right, how much time is shown?

 

RPM - is that running between 3000 and 4800 rpm, roughly? All in one gear?

 

What is "TPS" - is that voltage measured at the TPS? It seems related to RPM (as it should, of course) but I don't understand why they aren't going up and down together in some more orderly way?

 

Lambda - how/where do you derive a signal that says "the closed-loop is on or off" since it seems to have only two values like just on-and-off? Or some kind of O2 sensor voltage reflecting lambda value? What scale or just on-and-off?

 

I notice that after some of the nudges of the TPS curve, the "lambda" goes low (off?). But not after all TPS nudges and not after some slower movements or consistently - is that right?

 

Maybe stupid of me to not understand, but I would sure like to have your help with this chart.

 

Thanks.

Ben

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roger 04 rt

Hi Ben,

 

Not a problem, happy to explain. Answers below in parenthesis after each question. As an overview, I took this data using a GA-911 and a Netbook computer, riding from my house to the highway and then down the highway as part of learning before installing the LC-1. Are you a BMW MOA member? This page and the next has some data and narrative you might like: BMW MOA link. One caution, the link and the pasted narrative below had my early thoughts, they have evolves since then somewhat.

 

This is from a bmwmoa thread with that photo:

 

Made the highway run yesterday. Data below.

 

Data Points: 2,100

 

Driving RPM Range: 3,700 to 5,000 (roughly)

Injectors Fully Off: 3.3% of trip

 

Closed Loop O2: 47% of trip, up to 80% in steady throttle cruise

 

I observed two new things from this trip.

 

1. The highest correlation for closed loop operation is when the TPS (Throttle position) is steady. (I guess that shouldn't be a surprise.)

 

2. The Motronic will go into Closed Loop mode while the bike is accelerating through the gears. As each new gear was engaged, the Motronic started in Open Loop operation but would go Closed Loop while accelerating. This surprised me. When the bike is cold, it remains Open Loop. My thinking is this is why the motorcycle seems more driveable cold vs hot.

 

(I can only post one photo at a time so the shifting charts will follow.)

 

In the chart below (RPM, TPS and Lambda On/Off) you can see the effect of accelerating through a few gears in traffic on the left side (to 5th gear) of the chart (and dealing with changes in traffic speed). On the right half of the chart (to 6th gear). It is in closed loop a lot of the time.

RB

 

 

I have to confess that I don't understand that chart and hope you can take a moment to help me with some baby-steps.

 

Is it a a time series running from left to right? (Correct) If that's right, how much time is shown? (30 minutes, I think io remember.)

 

RPM - is that running between 3000 and 4800 rpm, roughly? (3700-5000 roughly) All in one gear? (every gear, normal ride, 5th, 6th on highway, which is right hand side.)

 

What is "TPS" - is that voltage measured at the TPS? (yes, scaled to fit the two axis chart) It seems related to RPM (as it should, of course) but I don't understand why they aren't going up and down together in some more orderly way? (when you open the throttle, it takes a while for rpm to build up. And once opened you can hold the throttle steady and rpm will continue to build.)

 

Lambda - how/where do you derive a signal that says "the closed-loop is on or off" since it seems to have only two values like just on-and-off? (that is right, it has two values, high is on and low is off. On the 1150 the motronic reports it to the gs-911.) Or some kind of O2 sensor voltage reflecting lambda value? What scale or just on-and-off?

 

I notice that after some of the nudges of the TPS curve, the "lambda" goes low (off?). But not after all TPS nudges and not after some slower movements or consistently - is that right? (yes, that was one of many things I learned as a took data. Given that an 1150rt ridden spiritedly is in CL half the time, I realized you could "fix" an 1150 without dealing with CL.)

 

Maybe stupid of me to not understand, but I would sure like to have your help with this chart.

 

Thanks.

Ben

Edited by roger 04 rt
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Peter Parts

Roger -

 

Very nice of you to try to clarify things for me and I had a close look at the link you provided (esp your post at 9:43), but I'd appreciate some specifics. There's no way to judge data except by understanding what is being collected.

 

Your trace is 15 minutes long? If that long, were you in one gear all that time and held the rpm pretty steady all that time? If it is 15 minutes, then things are happening in very slow motion between the traces?

 

Where does the "TPS" data come from? Did you measure voltage at a TPS pin? What's the scale or range? Why doesn't "TPS" more closely match "rpm"?

 

Your reply suggests the "lambda" curve is really some kind of picture of when the whole fueling system is spritzing or in abeyance??? The trace shows it going off for long periods of time while rolling. Do I have that wrong? From that kind of injector information, how can you tell if you are in closed-loop or map?

 

Thanks for help.

Ben

 

 

Edited by Peter Parts
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roger 04 rt
Roger -

 

Very nice of you to try to clarify things for me and I had a close look at the link you provided (esp your post at 9:43), but I'd appreciate some specifics. There's no way to judge data except by understanding what is being collected.

 

Your trace is 15 minutes long? If that long, were you in one gear all that time and held the rpm pretty steady all that time? If it is 15 minutes, then things are happening in very slow motion between the traces?

 

Where does the "TPS" data come from? Did you measure voltage at a TPS pin? What's the scale or range? Why doesn't "TPS" more closely match "rpm"?

 

Your reply suggests the "lambda" curve is really some kind of picture of when the whole fueling system is spritzing or in abeyance??? The trace shows it going off for long periods of time while rolling. Do I have that wrong? From that kind of injector information, how can you tell if you are in closed-loop or map?

 

Thanks for help.

Ben

 

 

Ben,

Did you see my specific answers to those questions, next to your questions in post 767380 in this thread?

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roger 04 rt

Ben,

 

Here are the answers from the earlier post below, slightly edited and colored for clarity:

 

I have to confess that I don't understand that chart and hope you can take a moment to help me with some baby-steps. (gladly)

 

Is it a a time series running from left to right? (Correct) If that's right, how much time is shown? (30 minutes, I think I remember.)

 

RPM - is that running between 3000 and 4800 rpm, roughly? (3700-5000 roughly) All in one gear? (every gear, normal ride, 5th, 6th on highway, which is right hand side.)

 

What is "TPS" - is that voltage measured at the TPS? (yes, scaled to fit the two axis chart) It seems related to RPM (as it should, of course) but I don't understand why they aren't going up and down together in some more orderly way? (when you open the throttle, it takes a while for rpm to build up. And once opened you can hold the throttle steady and rpm will continue to build.)

 

Lambda - how/where do you derive a signal that says "the closed-loop is on or off" since it seems to have only two values like just on-and-off? (that is right, it has two values, high is on (meaning the the fuel is being ramped by the motronic around 14.7:1) and low is off. On the 1150 the motronic reports it to the gs-911.) Or some kind of O2 sensor voltage reflecting lambda value? (not directly from a sensor just a status signal from the motronic saying that it is running the closed loop program) What scale or just on-and-off? (high is on, low is off, off means using MAP, scaled by AIT+barometric pressure+oil temp sometimes+adaptation values+battery voltage)

 

I notice that after some of the nudges of the TPS curve, the "lambda" goes low (off?). (yes, off) But not after all TPS nudges and not after some slower movements or consistently - is that right? (yes, that was one of many things I learned as I took data. Given that an 1150rt ridden spiritedly is in CL half the time, I realized you could not "fix" an 1150 without dealing with CL.)

 

Maybe stupid of me to not understand, but I would sure like to have your help with this chart. (if you haven't used a GS-911 it will take a while to get the hang of it but you will. Keep at it.)

 

Thanks.

Ben

 

Edited by roger 04 rt
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Peter Parts

OK.... the fog is lifting. I didn't see your replies at first. Thanks for going to the trouble of putting into red.

 

How does the GS-911 get a signal the ECU is closed-loop? Does the ECU output that information on a pin???

 

Then the GS-911 connects to the TPS wires?

 

I understand the contingency of TPS, rpm, etc. but the time-scale of relations seems odd. Given the half-hour time period, you must have been shifting gears dozens of times but the rpm trace doesn't reflect that any way I can see.

 

I think what is puzzling, also, is that these traces must be composed of many instantaneous sampled points. That would be 1500 over 30 minutes or once a second, roughly.

 

But it looks very different from the dyno traces many of us have run over the years; dyno traces have clear gear shifts, rpm changes, and torque outputs laid out in intuitive time sequence and orderly curves, just like riding down the road. But I am not yet able to read this chart as a half-hour trip?

 

Any further help greatly appreciated and I may be speaking for others who also are puzzled but are more reserved than I am about admitting my ignorance.

 

Thanks.

 

Ben

 

Ben

 

 

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roger 04 rt

Good, so let's keep going. You're correct this is much different information than a dyno run/plot. The GS-911 turned out to be a great tool for getting the Motronic to give enough information to learn a great deal about how it works. My aim was to confirm a method for accurately and reliably richening (or leaning) the fueling AFR for both Closed and Open Loop operation, and a method that worked in harmony with the Motronic, not against it.

 

The Motronic MA 2.4 has a single-wire serial data bus on the service connector. The GS-911 communicates with the Motronic over that bus. About once every 3/4 of a second, the 911 requests a status report from the Motronic of all its important values. Here is that list:

 

Time of sample

RPM

Oil Temperature

Air Temperature

Ambient Air Pressure

Battery Voltage

TPS Voltage

Ignition Angle

Ignition Dwell Angle

Fuel Injection Pulse Width

Lambda Sensor Voltage

Lambda Status (Closed Loop or Open Loop)

Tank Vent Status (On or Off)

 

The 911 also has a mode where it only requests Lambda Sensor Voltage so that it can make a pseudo-real time plot of the O2 sensor.

 

Below are some further answers.

 

OK.... the fog is lifting. I didn't see your replies at first. Thanks for going to the trouble of putting into red.

 

How does the GS-911 get a signal the ECU is closed-loop? (The Motronic reports it to the GS-911) Does the ECU output that information on a pin??? (Yes, on the serial bus pin on the service connector)

 

Then the GS-911 connects to the TPS wires? (No, the Motronic reports the TPS value over the serial bus.)

 

I understand the contingency of TPS, rpm, etc. but the time-scale of relations seems odd. Given the half-hour time period, you must have been shifting gears dozens of times but the rpm trace doesn't reflect that any way I can see. (If you look carefully at the left hand side of the chart you can see several instances of the TPS and rpm going up and down in quick succession, those are gear changes. On the right hand half you can see the rpm step down which was the shift from 5th to 6th.)

 

I think what is puzzling, also, is that these traces must be composed of many instantaneous sampled points. That would be 1500 over 30 minutes or once a second, roughly. (As I mentioned above it was 2,100 samples during that test ride, each sample being over a dozen different pieces of information.)

 

But it looks very different from the dyno traces many of us have run over the years; dyno traces have clear gear shifts, rpm changes, and torque outputs (but no motronic status information) laid out in intuitive time sequence and orderly curves, just like riding down the road. But I am not yet able to read this chart as a half-hour trip? (I was using a digital instrument, the GS-911 to get the Motronic to report what it was doing moment by moment--different than a dyno run, for a different purpose. There are some expanded plots over on bmwmoa that are easier to see some detail.)

 

Any further help greatly appreciated and I may be speaking for others who also are puzzled but are more reserved than I am about admitting my ignorance. (If you haven't used a tool or if you haven't used it for a planned purpose, it can be hard to see what is happening. Thank you for drawing out these answers and clarifications.)

 

Thanks.

 

Ben

 

Edited by roger 04 rt
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Peter Parts

Thanks again for going well beyond the call of duty in patiently explaining things.

 

I finally got off my butt and read about the GS-911. What a tool!!! And I have to admit, I would never have given the Motronic 2.4 credit for outputting all that data. Amazing.

 

It would be more judicious of me to say "If true... what a tool" since there are sometimes differences between claims and actual performance.

 

I sure wish I had one. But not likely I'll have my current OIlhead many more years*, so $300 hard to justify. Sad.

 

Back to digesting your great information.

 

Ben

*OK... I rode my 1961 R69s (highly sup'ed up) for 34 seasons. Wish I had it today. If I have my R1100S as long, I'd be selling it at 98 in 2038. Wouldn't that be a hoot.

Edited by Peter Parts
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roger 04 rt

This is one of those products that does what is says. They have even added features in the year I've owned mine. Last month they added more graphing and they doubled the sampling rate (just saw that today).

 

But you have to look at the matrix of features, by model. I don't believe that it supports realtime values for the 1100s.

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Peter Parts

The R1100S has the Motronic features of the R1150 series.

 

I am wondering if the GS-911 would reveal a lot about re-chipping - one of the real mod powerhouse methods? BeemershopMan himself mention the BB Powerchip (like I have sitting ready to be installed). Big questions about how chips modify spark, A/F, etc.

 

It might be possible to investigate these matters but it might be necessary to have some kind of standard "run" and compare before and after chips on that standard run.

 

A dyno is such a standard run, so to speak, because it programs the load.

 

Ben

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roger 04 rt

 

 

My guess is that a GS-911 wouldn't give that kind of insight as effectively as a dyno.

 

I went to the BBPowerchip site. It's amazing to me that the chip guys say almost nothing on their sites about how their products work. I did pick up this though since they don't seem to mind talking about why other products don't work:

 

"Note:

We warn people urgently not to use gasoline pressure regulators with a higher pressure. (from K-model).

The consequences are more excessive fuel consumption and soot formation and thinning of the oil of the engine.

Big air snorkel called air charger worsen the torque in the lower range,  these make only sense from stage 4 on.

Pieces of equipment like PowerCommander, Techlusion u. a. work after unfortunately not as desired our experience and almost always supplies drastic disturbances instead of to an improvement.

Special plug leads are insignificant and from our view pure financial waste , absolute no power gain."

 

Also BTW, here is what Dobeck Engineering says about its Techlusion product in its support forum:

 

"In order to make any fuel adjustment within light loads and normal cruising we must bypass the narrowband O2 system. Without bypassing the system as we add fuel the stock ECU would just pull it back out and cause bad drivability. We can not simply disconnect the O2 sensors because this will throw an [error code] on most vehicles."

 

So nothing important is being done by its connection to the O2 sensor.

Edited by roger 04 rt
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Peter Parts

Right - nice folks at Techlusion told me 5 yrs ago they were negative on the O2 sensor. Should be self-evident when you think about it.

 

And Bernard Bernt (BB PowerChip) is a pretty helpful guide, even if his English is no better than my German. But rumor has it that BBP is one of the few chips that addresses spark timing with its 6 progressive stages. The folks at Rhineland West (or something like that) kind of told me they also move the spark on their chip.

 

The folks who promote Laser exhausts on this continent, are low on my list of honorable dealers, and they generally do not claim to influence spark timing. (Maybe that is why BMW used their product - paradoxical as that may sound.)

 

But spark timing's about the only place to find the horses, aside from major surgery on the engine (like I've done before). BMW has always (speaking only of the last 50 years) kept a large safety margin - at the expense of power. Bless 'em. As long as you are very broadly within the A/F ballpark, it has little influence on horsepower.

 

If you have the BBP, you can make a handlebar mounted switch tied to the cat code plug socket and try each map as you roll down the road.

 

Ben

Edited by Peter Parts
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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.

 

 

 

 

Edited by roger 04 rt
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roger 04 rt
Right - nice folks at Techlusion told me 5 yrs ago they were negative on the O2 sensor. Should be self-evident when you think about it.

 

And Bernard Bernt (BB PowerChip) is a pretty helpful guide, even if his English is no better than my German. But rumor has it that BBP is one of the few chips that addresses spark timing with its 6 progressive stages. The folks at Rhineland West (or something like that) kind of told me they also move the spark on their chip.

 

The folks who promote Laser on this continent, are low on my list of honorable dealers, and they generally do not claim to influence spark timing. But that's about the only place to find the horses, aside from major surgery on the engine (like I've done before). As long as you are very broadly within the A/F ballpark, it has little influence on horsepower.

 

If you have the BBP, you can make a handlebar mounted switch tied to the cat code plug socket and try each map as you roll down the road.

 

Ben

 

As long as these "rechipped" Motronic run Closed Loop, these chips can only affect:

 

--fine tuning of the fuel map for a better closed loop starting point. But it's not clear to me why this is of value since the Motronic has a good capture range. Richen WOT.

 

--Change the spark-timing and dwell maps.

 

However, they don't say on their site that they do any of these things in the chip.

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roger 04 rt
Can a "chip" remove the feedback system?

 

Ben

 

Yes they could disable closed loop. But it would require a bootleg copy of the code or back-translating from the binary--an expensive, time consuming task. It doesn't seem likely to me.

 

Finding the fuel and spark data tables is certainly easier, unless you have a bootleg copy of the code, than reverse engineering the source code. The gains for an unmodified R11xx, according to their graphs (which also mention the use of cats), are above 6000 rpm. That being the case the chip MIGHT richen open loop mixtures above 80% throttle. They MIGHT also be able to advance the timing. An interesting note is that they mention gas mileage is about the same, suggesting that there is not fuel being added in most of the cruising rannge.

 

Dirtrider asked to to look at peak advance in my data sets. He thought it would be 43 degrees, sure enough, the peak value I found was 42.96. So do they advance beyond that or just go to that limit more often? It's anyone's guess since they don't say a word.

 

Other graphs on their site show gains for pistons, cams and exhausts. Believeable, and with closed loop adaptation, the 1150s might even be able to learn the increased VE and apply it to open loop. If that happened, other than for hypothetical spark advance, no modified chip would be needed.

 

The last possibility, and I want to mention it since I've read it in a reputable publication, is that the replacement chip is merely a copy. Looking at their site they would have to have reverse engineered, and remeasured a lot of VE configurations, given the scope of of their piston, cam and exhaust product line.

 

You might be able to use the GS-911 to measure before and after spark advance but it could be hard to correlate the data.

Edited by roger 04 rt
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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.

 

 

 

 

Where would you get matched injectors? Is there someone that bench tests injectors and offers matched sets?

Link to comment
Peter Parts
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.

 

 

 

 

Where would you get matched injectors? Is there someone that bench tests injectors and offers matched sets?

 

I posted about that recently somewhere around here.

 

http://www.rceng.com/

 

or just take three or so to the shop and match.

 

BMW are rumored to be not outside 10% which is little comfort, eh. Mine are just a few percent apart. Matching of injectors is both in terms of flow and for spray dispersion - so RC injectors might be better quality than stock from the start.

 

Ben

Edited by Peter Parts
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Peter Parts

Roger -

 

Your well-informed and well-intentioned posts are a treat. But in your writing, there are times when I have trouble separating statements "that any rational person would certainly agree with as plausible inferences" from things you know for sure as facts or from some kind of intermediate level of certainty.

 

Given the slippery nature of truth about the Motronics, that can be an important distinction.

 

An example is your comment about after-market chips and feedback or reverse engineering.

 

Ben

Edited by Peter Parts
Link to comment
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.

 

 

 

 

Where would you get matched injectors? Is there someone that bench tests injectors and offers matched sets?

 

I posted about that recently somewhere around here.

 

http://www.rceng.com/

 

or just take three or so to the shop and match.

 

BMW are rumored to be not outside 10% which is little comfort, eh. Mine are just a few percent apart. Matching of injectors is both in terms of flow and for spray dispersion - so RC injectors might be better quality than stock from the start.

 

Ben

 

Thanks for the RC Engineering link. I am not sure which injector is the right one for our bikes, but that seems like a reasonably priced solution for balanced, calibrated injectors. If anyone goes that route, I'd be interested in which injector you buy.

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Just a quick comment about balanced injectors. The GAMI article Roger referenced is talking about aircraft engines. These are large displacement, low rpm, low to moderate horsepower engines with mechanical fuel injection designed to run at constant speed for extended periods of time. I have no idea how mechanical injectors compare to our electronic models, but the differences could be significant. Aircraft fuel injection systems have no closed loop operation to try to balance out cylinders, another significant difference. I would be hesitant to go looking for a solution to a problem that may not exist.

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roger 04 rt

I don't disagree with Karl's conclusion but would like to point out some differences.

 

The author did reference an aircraft engine but he stated that his work was relevant to all spark ignition engines. I don't see that HP or RPM are relevant to the discussion, but I think it is a good point that none of us know whether our injectors match well or not. That is one of the reasons I mentioned the patent a couple posts ago.

 

Many of us have taken great care with valve adjustments and throttle body balance. At the same time we know little about two equally important parts of the fuel injection process: the O2 sensor and the fuel injectors. (For the O2 sensor we have no way to measure its AFR switch point or its response speed--more below)

 

Yes, the patent article talks about continuous flow injectors. The imbalance was a few to several percent. The good point of this kind of injector is that it is always on. The injectors we use in the r11xx bikes are turned off and on every 360 degrees. Not only can the fuel injectors have flow mismatch like the aircraft continuous flow type, but the time it takes to turn them on can vary (Edit: see this link that I found just after posting this Pulse Turn On Time), creating the possibility that at light to mid throttle the mismatch can be even greater than just the flow rate differences. But again, there's no way to test or adjust them at home. We adjust the valves and TBs but because we can't measure or adjust FIs, most of us have to ignore that half of the equation.

 

There are solutions: measure the injectors at a specialized shop, or run richer mixtures so that the engine is operated near Best Power where, due to lack of oxygen, injector imbalance is less significant. Out of curiosity, I'm going to have mine measured--sample of one pair--then decide what I think of any differences. In the meantime I'm running a slightly richer mixture and getting more low RPM torque and smooth running as a benefit.

 

Here are some additional thoughts on injector imbalance and O2 sensor interaction:

 

... On our two cylinder Boxers, if one cylinder is leaner than the other due to injector mismatch, three things can happen in closed loop: 1) Because the average of the two cylinders has to be 14.7, one cylinder is leaner than the other meaning the lean one has an excess of oxygen and while the rich side is depleted of oxygen. The spread between them is related to the fuel injector imbalance in a valve/TB tuned engine. 2) The time for the Motronic program to go from lean to rich and rich to lean is extended because only one cylinder is contributing the oxygen that the Lambda sensor responds to. 3) As the time for the cycle goes up, the fuel ramp in closed loop gets larger, meaning there is a greater modulation of the fuel supply.

 

The consequence in the leaner cylinder to the longer higher ramp of fuel, is a modulation of that cylinder's power output. While that is happening, the richer cylinder, depleted of oxygen, has an almost insignificant change in its power. The peak to peak variation of fuel can reach 8% or more (especially if the Lambda sensor is old and slow). So the leaner cylinder's power is fluctuating several percent. This can be felt.

 

Since there are still many surging R1100/1150s around, I offer this as food for thought, to be factored into diagnosis, not as a remedy for every bike.

Edited by roger 04 rt
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roger 04 rt
Roger -

 

Your well-informed and well-intentioned posts are a treat. But in your writing, there are times when I have trouble separating statements "that any rational person would certainly agree with as plausible inferences" from things you know for sure as facts or from some kind of intermediate level of certainty.

 

Given the slippery nature of truth about the Motronics, that can be an important distinction.

 

An example is your comment about after-market chips and feedback or reverse engineering.

 

Ben

 

Thanks for the kind comments. I try to use words like might or could for inferences or deductions and use words like data, measured or read for things that seem more certain to me.

 

Regarding the aftermarket so-called performance chips, I have background in control-system source code development and am familiar with the back-translation process. So I know the costs in manpower and time for that effort. So it's not impossible but it's not easy either, and they make so many exhaust types for a large mix of cars.

 

With so many R bikes around and my work on my own, I'm trying to expand the discussion though measurement, testing and research. How each owner uses the info is enviously up to them.

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Here's a curve of injector latency versus battery voltage

Sorry, how does this relate at the moment?

Anything past 15Vdc is pointless as our systems, bike or car (assuming it's your normal 12Vdc system) do not ever go past these voltages. Otherwise our batteries would be getting "cooked".

Any voltages below 12Vdc are irrelevant as well, as even if your bike/car would be for a short time below that voltage, once the engine is running/ the charging voltage will very quickly go above 12Vdc and head towards +13Vdc in the moment the engine get's revved above idle speed.

 

So our interested area of concern should be 12~15Vdc, where we are looking at around a 0.4ms window.

This latency would have a larger influence at higher rpm (at which the battery voltage/charging voltage will be higher and as such latency will be reduced again), due to the possible higher change in % angle before/after TDC.

 

I don't think that there is any relevance as if it would have...then I am sure the manufacturer would(uses) use a Regulator in the injector circuit to keep the voltage stable and as such have a "known" percentage of latency.

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roger 04 rt
Here's a curve of injector latency versus battery voltage

Sorry, how does this relate at the moment?

Anything past 15Vdc is pointless as our systems, bike or car (assuming it's your normal 12Vdc system) do not ever go past these voltages. Otherwise our batteries would be getting "cooked".

Any voltages below 12Vdc are irrelevant as well, as even if your bike/car would be for a short time below that voltage, once the engine is running/ the charging voltage will very quickly go above 12Vdc and head towards +13Vdc in the moment the engine get's revved above idle speed.

 

So our interested area of concern should be 12~15Vdc, where we are looking at around a 0.4ms window.

This latency would have a larger influence at higher rpm (at which the battery voltage/charging voltage will be higher and as such latency will be reduced again), due to the possible higher change in % angle before/after TDC.

 

I don't think that there is any relevance as if it would have...then I am sure the manufacturer would(uses) use a Regulator in the injector circuit to keep the voltage stable and as such have a "known" percentage of latency.

 

Hi Alfred02,

 

All good questions. My main reasons for showing that curve was to confirm the approximate turn on time, and to show that it varies with battery voltage. And of course I know as well as you that the higher and lower voltages on that chart are mostly irrelevant, although cranking voltages do drop, especially if you have a weak battery, I saw 11V the other day on mine (I need a new battery).

 

I'm going to answer your questions/comments in the context of an R11xx engine that doesn't run its best at a 14.7:1 closed loop mixture unless things are really well balanced. That's why we get our valves to less than one thousandth, and balance our throttle bodies at multiple RPMs, with a precision differential instrument. I noted earlier that we give almost no attention to fueling imbalances which are just as important to total cylinder power balance. (Nor the O2 sensor)

 

Your last point, if battery voltage variation was an issue the manufacturer would use a regulator, is valid. And it turns out the manufacture does regulate for battery voltage at the fuel injector. The way it is done is: the Motronic measures the battery voltage, and then looks up in a table what the "net dead time" is and adds that into the fueling calculation.

 

I added the curve to this thread becasue it shows just how large the "net dead time" meaning the time that the Motronic must add can be--roughly 1 mS at 13.8 volts. At idle, the injector fuel pulse is in the vicinity of 2 mS and at 3500 RPM cruise, about 3.5 mS. So the net dead time is half the idle pulse and almost 1/3 of the 3500 RPM cruise. Any net dead time difference between the injectors will have a significant difference: a 0.1 mS difference would be 10% of the fuel on time at idle, and 4% at 3500 RPM cruise.

 

Here is a picture that gives an even closer look at how they work.

 

injdeadtimes4.png

 

In the picture you can see that net dead time is comprised of:

--delay to start turning on

--time to ramp up

--delay to stop

--time to ramp down

 

Another point: the 7 mS time is the total injector time in my example too since our Boxers fire the injectors twice per combustion cycle--half the fuel twice, with two dead time cycles. So my 3.5 mS per injection, doubled is very close to the example given above.

 

So my points on injector imbalance are that there can be different flow rates and different net dead times, and both are important. And for those of us trying to balance our cylinder power AIR (valves and TB) are one side of the equation and FUEL accuracy is the other. Both are equally important, UNLESS you run a mixture richer than 14.7:1. If you run at 13.8, where all the European CO potentionmeter motorcycles were set, you are almost insensitive to small fueling differences, up to several percent. Then a good TB and Valve job gets it about right.

 

More food for thought.

RB

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  • 1 month later...
roger 04 rt

Yesterday afternoon I disconnected the Wideband O2 sensor so that I could measure the "raw" or Open Loop, Air Fuel Ratio (AFR) of the Motronic MA 2.4., with Pink Coding Plug. And then measure the Open Loop effect of the BoosterPlug. The motorcycle is running 93 Octane E10 fuel, which is important since it has shifted the curves upward by about 4%, meaning running 4% leaner.

 

In all the charts, there are two marker lines, one is at 14.7:1 (normal Closed Loop stoichiometric) and 13.8:1 (my richer Closed Loop target that creates more power). In the first photo there are two charts: the top chart is Open Loop, the lower Open Loop plus BoosterPlug.

 

The top chart below shows Open Loop AFR, after the Motronic is reset, and from a Cold start. For the first three minutes, you can see the AFR moving from 13:1 to the low 15s as the bike oil warms up. If I were running pure gas, the warmup would be in the 14.7 range, but E10 leans out the mixture. Much of the cruising time, the AFR is between 15:1 and 16.5:1--fairly lean. Notice in the histogram inset chart that the bulk of AFRs are between 14:1 and 16:1, even including acceleration.

 

The in the lower chart, the bike is warm, the Motronic is still reset but a BoosterPlug has been connected, dropping the air inlet temperature (AIT) signal to the Motronic by 20C. There is a similarly large spread of AFRs, but now they run between 13:1 and 15:1, about 6-7% richer. I was surprised at how much the AFR varies in Open Loop operation.

 

afropenbp.jpg

 

For comparison, look at the next photo, the conditions are reset Motronic, no BoosterPlug and Closed Loop at 13.8:1. The upper run is the first test run after reset and the lower run is the second run after reset. Since the Motronic is only Closed Loop about half the time in these charts, and comparing these two runs to the first photo (Open Loop conditions), you see Adaptation, the learning of Closed Loop applied to Open Loop conditions, and in the second run looking at the even tighter spread of AFRs, further Adaptation.

 

afrresetadapt1.jpg

 

Some conclusions:

 

1) E10 fuel results in leaner Open Loop operation

2) Open Loop fueling results in a wide variation of AFRs

3) The BoosterPlug does enrichen the fueling tables by 6-7%

4) Closed Loop operation tightens the fueling range

5) Closed Loop operation allows the Motronic to correct for E10, aging injectors and air filters, and variations in battery voltage and fuel pressure.

6) The Motronic is a learning, adapting engine controller that takes what it measures in Closed Loop operation and applies it to adjust Open Loop fueling. (The mechanisms and degree could be examined further.)

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This is most interesting Roger. This data has convinced me that I want nothing to do with late model Beemers or late model anything when it comes to motorcycles. At yesterday's Big Twin airhead get together several guys expressed their opinions pertaining to ECU controlled motorcycles and I must say I mostly agree with them.

Must be my age is showing. :D

Edited by JamesW
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roger 04 rt
This is most interesting Roger. This data has convinced me that I want nothing to do with late model Beemers or late model anything when it comes to motorcycles. At yesterday's Big Twin airhead get together several guys expressed their opinions pertaining to ECU controlled motorcycles and I must say I mostly agree with them.

Must be my age is showing. :D

 

Bosch and others have done themselves a disservice by being so secretive. At their cores, ECUs are fairly simple:

 

1. Read TPS (or Manifold Pressure) and RPM, look up an injector on-time

2. Adjust for air temperature, air pressure and battery voltage

________Adjust for Oxygen Sensor feedback

________Add fuel if the oil is cold

3. Fire the injector

 

The devil here is servicing the needs of the catalytic converter. It needs to get a flow of exhaust gas with a little bit of oxygen followed by no oxygen to keep the cat happy. That means constantly varying the fuel by a several percent around a 14.7:1 air-to-fuel ratio. A good byproduct is that as the ECU (Motronic) learns how much adjustment is needed to hit 14.7:1, it learns about engine "wear" (injectors, air filter, throttle bodies, cylinder carbonizing, etc.) and adds some corrections.

 

Although the engine is happier with the excess fuel of a 13.5:1 mixture, the cat is happy only around 14.7:1 with the result that the cylinder head and exhaust gas temperatures are hottest and the mixture is just lean enough to be sensitive to small changes in air and fuel--and we can feel it. At this point there are a couple choices:

 

--Keep our bikes super-tuned and live with the rough edges.

 

--Find ways to richen the mixture and enjoy performance more like "the good old days". (But knowing that the Motronic will do everything in its power to negate your attempts.)

 

I'm starting to grow fond of the Motronic 2.4 and think of it as the new, old days.

 

 

Edited by roger 04 rt
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... At this point there are a couple choices: ...

Or install a Power Commander USBIII with a wideband O2 sensor. In that case the Power Commander will take over closed-loop operation so you can set the value to be anything you like, and you also can tweak the open-loop map if desired. All easily settable by a laptop computer, and you can save and apply various configurations at will making testing very easy. You can even directly read realtime A/F ratio (as read by the wideband sensor), injector duty cycle, rpm, throttle position,. etc. on the laptop, or an external gauge.

 

As for me I ended up with a 14.2:1 closed loop setting (best compromise I could find between throttle response and fuel economy, and even at that it is notably better than the very lean stock setting) and I richened the open-loop mixture a bit in the 'surge range' (<5% throttle position and between 3-4000 rpm.) Everything else stock. This has worked well for me on an 1100RT.

 

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