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#767948 - 03/25/12 06:13 PM Re: GS-911 wideband O2 project details [Re: NJNeal]
TestPilot Offline
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Registered: 05/27/07
Posts: 450
Loc: Williamsville, NY
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.
_________________________
Karl
2007 R1200ST

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#767987 - 03/25/12 09:42 PM Re: GS-911 wideband O2 project details [Re: TestPilot]
roger 04 rt Online
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Registered: 11/27/11
Posts: 1815
Loc: Massachusetts
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 (03/25/12 10:10 PM)

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#767989 - 03/25/12 10:02 PM Re: GS-911 wideband O2 project details [Re: Peter Parts]
roger 04 rt Online
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Registered: 11/27/11
Posts: 1815
Loc: Massachusetts
Originally Posted By: 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


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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#767995 - 03/25/12 10:51 PM Re: GS-911 wideband O2 project details [Re: roger 04 rt]
roger 04 rt Online
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Registered: 11/27/11
Posts: 1815
Loc: Massachusetts
Here's a curve of injector latency versus battery voltage



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#767999 - 03/26/12 12:10 AM Re: GS-911 wideband O2 project details [Re: roger 04 rt]
Alfred02 Offline
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Registered: 05/12/11
Posts: 790
Loc: NSW Mid North Coast Australia
Originally Posted By: 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.
_________________________
BMW 2014 R1200RT-SE/LC
BMW 2005 R1200RT-SE (Traded in 03-2014)
BMW 2004 R1150RT (Traded in 02-2012)

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#768021 - 03/26/12 06:41 AM Re: GS-911 wideband O2 project details [Re: Alfred02]
roger 04 rt Online
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Registered: 11/27/11
Posts: 1815
Loc: Massachusetts
Originally Posted By: Alfred02
Originally Posted By: 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.



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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#774600 - 04/29/12 07:01 AM Wideband O2 & Open Loop Fueling [Re: roger 04 rt]
roger 04 rt Online
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Registered: 11/27/11
Posts: 1815
Loc: Massachusetts
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.



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.



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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#774636 - 04/29/12 10:45 AM Re: Wideband O2 & Open Loop Fueling [Re: roger 04 rt]
JamesW Offline
Member

Registered: 11/23/04
Posts: 805
Loc: Baker City, Oregon
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. laugh


Edited by JamesW (04/29/12 10:46 AM)

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#774795 - 04/30/12 06:35 AM Re: Wideband O2 & Open Loop Fueling [Re: JamesW]
roger 04 rt Online
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Registered: 11/27/11
Posts: 1815
Loc: Massachusetts
Originally Posted By: JamesW
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. laugh


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 (04/30/12 07:05 AM)

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#774853 - 04/30/12 12:27 PM Re: Wideband O2 & Open Loop Fueling [Re: roger 04 rt]
smiller Offline
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Registered: 03/27/04
Posts: 12236
Loc: Asheville, NC
Originally Posted By: roger 04 rt
... 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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