2009 GS lean mixture, harmful???

Discussion in 'GS Boxers' started by carlesonra, Jan 7, 2013.

  1. carlesonra

    carlesonra n00b

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    While checking valves on my 2009 1200GS at 40,000 miles, I noticed spark plugs showing a lean mixture. I have a K&N installed but no other change and realize manufacturers have clean running as a priority. Question is: are other riders showing light spark plug coloring which is kinda normal or Is this something that needs attention and if so what? I have not noticed any spark knock when pulling at lower rpm.
    Thanks for your time in responding.
    Bob Carleson
    Arroyo Grande, CA
    R1200GS, R80RT, DR650
    #1
  2. def

    def Ginger th wonder dog

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    It is generally understood that current piston engines are fueled lean to meet emission requirements. In the boxer engine, this can be troublesome causing detonation, higher combustion chamber temperatures, driveability issues and reduced engine output. Later boxers employ knock sensors to detect and offset the issue of detonation.

    In our attempts to improve performance, many boxer owners install free flowing exhaust systems, high flow air filters and other gadgets in an attempt to make more noise and more power.

    Upon doing so, we see questions and comments such as yours regarding the appearance of lean fueling conditions. And while few boxer owners report engine damage, there seems to be an increase of the installation of aftermarket pipes and air cleaners. These pipes and air cleaners promote more engine air flow but do nothing to increase fuel flow. If you insist on aftermarket pipes and air cleaners, be prepared to spend more on electronics to increase fuel delivery along with the increased air entering your engine.

    Over Christmas, my son trailered his Honda V-twin here to Alabama. One morning it would not cold start. Removal of the air cleaner showed why. The oil from the K&N had settled in the carburetor and choked off the pilot jet as well as left deposits on the carburetor slide. A spray with carb cleaner got things running again. But, it was evident from a plug check that the A/F mixture was way off.

    If you insist on aftermarket air cleaners, be sure they provide effective cleaning of the air entering the engine. Some studies show these aftermarket air filters pass considerable dirt compared to the OE paper air filter. You have been warned.
    #2
  3. Disco Dean

    Disco Dean Long timer

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    This is normal.

    Your bike will compensate for any modifications you do to the bike ie. exhaust or filter will not change the mixture.

    As noted here in a number of posts - BMW and other manufacturers run their bikes quite lean - in my experience BMW has always done this. Mainly for emissions regulations and pollution control.

    One of the reasons some use "booster" plugs and such to trick the bike into running a bit richer. Again posted on here quite a bit.

    Do not worry - and if you are really concerned take it in for diagnositics and they will be able to tell if all is well pretty quickly.

    Dean
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  4. 2712

    2712 Been here awhile

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    plus one on that:clap
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  5. Disco Dean

    Disco Dean Long timer

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    Def,

    The fuel and mixture monitoring sensors on the bike - of which there are a few - are all situated after the air filter and before the exhaust - cat and free flowing aftermarket cans.

    The computer in the bike continually monitors the system and adjusts the fuel mixture to suit - no change in air filter or exhaust will change the fuel mixture at the engine. The bike is continually compensating for this.

    That is why these bikes continue to be perfectly tuned when starting cold, or in colder or warmer ambient temps (barometric pressure) as well as not being affected by altitude - the wonders of electronic fuel injection.

    The BMW and other bikes even have a delay in this change depending on other factors like time you have run the bike while riding and consistency of your riding - ie. if you have done long hauls of highway riding the bike will delay the change in fuel/ignition due to riding style. That is why when you sometimes leave the highway and go through a few stops the bikes seems to be running extra lean or doesn't run right - until the computer figures out you are not on the highway again and changes - Harleys are notorious for taking a long time - all pre-programmed into the bikes.

    As I noted many posts ago - when we attempted to change to fuel mixture characteristics of our BMW R - race bike by modifying both the exhaust and air chamber/filter we could not do this no matter how aggressive we were - the bike adjusted for it in all respects. The only way to do this is by either tricking the sensors - or by reprogramming the computer.

    So aftermarket filters and exhausts (provided they have O2 sensors) and the filters actually filter the air - are completely safe and will not change the "leaness" mixture in the combustion chamber at all.

    The bikes are too smart.

    Now oil in the filter bunging up a carb is another issue and I do not use K&N because of those exact issues before and numerous testing that suggests either foam or standard oem paper is better but this isn't an air filter thread is it...:D
    #5
  6. Marki_GSA

    Marki_GSA Long timer

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    Sorry but your statements are completely at odds with my own and many others experience as far as the 1200 GS is concerned. Yes they can compensate but not indefinitely and a free flowing air filter at sea level will definitely take it out of bounds. There is only so much extra fuel in the map bins and once your outside the boundary your into mixture problems. O2 sensors by the way only trim mixtures in a closed loop situation I.E cruising. Outside this area they have no affect at all as they are only lambda sensors and not wide band sensors.
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  7. Disco Dean

    Disco Dean Long timer

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    As far as I know the BMW has a barometric pressure sensor (altitude) in the main comp unit, the O2 sensors, intake temp and pressure sensors as well as the knock suppression sensors and engine temp sensors to balance and accommodate the variables of operation. (As far as I know) Just my experience of course and I am not a BMW engineer or tech so do not have access to the actual figures and mapping comparisons - however my own experience on the track and the dyno with the BMW Cup bikes saw no change in the mixtures with various number of exhausts, cut and reformed air-boxes, and more than a few air filters including no filter at all. This was a few years ago. This involved many long hard hours in the shop and the only solution was getting access and clearance from BMW to use the BMW computer program to modify the mapping - they didn't want to do that of course.

    My comments also come directly from a very good friend and racing buddy of mine who is the owner of a multi brand BMW dealership and his main BMW tech. As I posed the same questions in response to our experience with the 1200 on the track to them and my sometimes rough running bike after long hauls.

    Maybe we didn't get outside of the parameters you talk about - perhaps - but with my own R1200GS "2006" I also saw no visible signs or change in spark plug colour with the addition of a K&N, OEM paper and now my oiled foam air filter - or my full cat-free Laser exhaust and headers. And that accounts for over 100k of mileage and many different filters and two exhausts - and approx 7 sets of plugs as I change them every year.

    As the BMW paper air filter as tested and commented on this forum flows more air than an oiled K&N or even my oiled foam filter - I would think that would richen the bike and not lean it out - but again no change.

    After all is said and done - I don't have specific data that I can show you to back any of my comments so they are just that. And, you know we could have screwed it all up too... you never know.:cry

    Take it for what you will.
    #7
  8. Marki_GSA

    Marki_GSA Long timer

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    The GS range to my knowledge doesn't have a MAP/barometric sensor. If it does it is very well hidden and doesn't show on the GS911 software. When I get time/weather I will do a back to back run with a wide band sensors and post the logs. Don't get me wrong, I am not saying your in the realm of engine damage. You can quite easily find yourself with less than optimal running though. Usually quite the opposite from what you wanted from tuning options.
    #8
  9. MotorradMike

    MotorradMike MIL-TFD-41

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    The OP has an '09 bike.

    Some of the responses in this thread are about older bikes, including one with a friggin' carburetor.
    Best leave the older BMW boxers out of it as they assume air mass by measuring throttle plate angle.
    Apparently, that has been improved upon.
    #9
  10. Marki_GSA

    Marki_GSA Long timer

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    Mine is an 09 and that's what I am referring to. The 2008-2009 bikes were the worst for running lean out of all of them. The cam head improved a bit over them
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  11. Chip Stevens

    Chip Stevens Been here awhile

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    Spark plug color is not the best way to determine fuel air ratios. In aviation we determine rich or lean off cylinder head tempature peak. If you google Gami Injectors and spend some time researching you will see that many turbocherged aircraft are running 50 degrees lean of peak where the tempatures are cooler then at peak. All this is irrelevant if you are running less then 75% power. Power is determined by RPM and manifold pressure. Much above 5000 ft a naturally aspirated engine can't get more then about 75%. In other words if you are below 5000ft running full RPM and full throtle for more then two minutes you aren't likely to do any damage rich or lean. chip
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  12. DrLax

    DrLax Go Big

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    I have an 09 GSA. OEM filter and stock exhaust. The plugs are light colored. It also pings at low rpm and high temperatures.
    #12
  13. def

    def Ginger th wonder dog

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    Mike, While my comments included an engine with a carburetor, the example was intended to show that oiled air filters can cause problems and pass more dirt than the OE filter. As for the newer BMW boxer engine management, they still run lean to please the EPA.
    #13
  14. roger 04 rt

    roger 04 rt Long timer

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    Most of Disco Dean's comments are correct.

    There is some good information in this thread and some wrong information. I've ridden around most of the last year with a GS-911 and Innovate Motorsport LC-1 Wideband O2 sensor logging AFRs continuously. My motorcycle is an R1150 but it would be hard to believe that the newer machines don't have all of the EFI features of the R1150. I've seen R1200 GS-911 data and there are more features reported.

    Here are some important things to know:

    1) there is not an intake manifold MAP (manifold absolute pressure) sensor. The Motronic's use the TPS and RPM to do the basic fueling.

    2) there is a barometric pressure sensor on the ECU and it does adjust for altitude.

    3) on a typical ride the motorcycle is closed loop 40-50% of the time. When closed loop the mixture is always a few points from lambda=1 which is 14.7:1 for pure gas and 14.1:1 for E10. This is true even if you add intakes and exhausts. My data says that closed loop has roughly a +-20% range. Very large.

    4) when closed loop, the Motronic learns how far off your particular engine is from standard: battery, fuel pressure, fuel type, airflow, sensor errors, etc. What it learns in closed loop it applies broadly to all Open Loop fueling—including WOT and warmup. The correction factors are called Adaptation Values and are referred to in the 1150 manual and for the 1200 I've seen them in the GS-911 documentation.

    5) closed loop adjusts very quickly, less than a few seconds in all cases. Long Term adaptation values take longer depending on how you ride. Steady driving at various speeds, RPMs and load helps it learn faster.

    6) All these bikes run equally lean from R1100 to R1200 but some run better on the lean mixture than others. For example the 1150s and 1200s from '04 on have two plugs per cylinder which help it burn the lean mixture. 1200s on have two O2 sensors. Closed loop AFR and adaptation get calculated per cylinder. This way you don't have one cylinder leaner than standard and one richer than standard.

    To remedy the lean running the simplest thing to do is to replace the stock lambda=1 sensor with a Wideband sensor that allows you to program lambda 4-6% more fuel works wonders. The cost is about $160 per O2 sensor. I've got all th info published in two Wideband threads here. So a mixture between 13.8 and 14.1 (for gasoline) leads to a great running bike--no pipes, no filters, no dyno tuning needed.

    If you want my opinion on why intake filters and exhausts affect running ... And since I haven't seen anyone log data on this ... I would guess that since the intake and exhaust systems are tuned, putting aftermarket parts on leads to LESS air in the cylinder in the mid range. Less air means less power. Until someone logs the AFR at various RPMs and loads, all we'll have are opinions.

    Regarding the aviation comment, its at about 7500 feet where naturally aspirated engines hit 75% power, however the guest of that comment is correct.
    #14
  15. roger 04 rt

    roger 04 rt Long timer

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    Light spark coloring is normal in engines with O2 sensors. As has been said many times. Through this thread.

    Interestingly, I have used a Wideband O2 sensor to add 6-8% to my fueling and the plugs still are light. (Below) how do your plugs compare to mine?

    The mixture set by the narrowband O2 produces the highest exhaust gas temperature. Go richer and the EGT drops and surprisingly to some (but not pilots of piston engines) the EGT gets cooler as you go leaner.

    Here is an Autolite Plug with 2,000 miles of mostly local driving at 13.8 which means 6% richer.
    [​IMG]
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  16. roger 04 rt

    roger 04 rt Long timer

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    As I mentioned a couple posts ago, all R series motorcycles have a barometric sensor buried in the ECU and the GS-911 does report it, see the data from an R1150 below. Ambient air pressure is column F.

    It's my opinion that changing the exhaust or intake changes the tuning dynamically of the air flow based on what I've read in numerous books. When an exhaust pulse leaves the engine a pocket of high pressure air leaves the cylinder when it hits a change in exhaust geometry (e.g. wider or narrower pipe, the catalytic converter, etc.) some of that pocket of air reflects and travels back to the exhaust valve, we're talking thousandths of a second here. If the reflected pulses pressure is high while the exhaust valve is still open, less air fills the cylinder when the intake opens. If the pressure from the reflectednpulse is low at that moment, more air goes in when the intake valve opens. These dynamic conditions change with RPM. When you put on an aftermarket exhaust or intake you may change these dynamics which BMW has carefully measured and accounted for the the VE (volumetric efficiency) also know as the Fuel table.

    [​IMG]
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  17. Disco Dean

    Disco Dean Long timer

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    Very cool and yes I was sure that the ECU had those functions (especially in the newer models of R bikes) From my experience the comments you make about "pulse' etc. is correct and most times are accommodated but are most important in very highly tuned engines. Most specifically in engines that take advantage of megaphone exhausts - when building a cam or engine timing in conjunction with the properly calculated taper and exhaust length & carb intake length one can in effect use the shock wave/pulse to hold gasses in the cylinder a little longer allowing for more aggressive valve overlap etc. making it possible to change up and be more aggressive with your cam timing and profiles - many many different factors to think about. However that is some very fine tuning and normally only reserved for racing applications as well as older megaphone exhaust systems. ie. Norton Manx singles or Honda 5 cyl multies. The benefits of doing this on a modern bike are largely negated when you have cross over exhausts, 4 into 2 into 1, cats, and non-megaphone exhausts. Much why we see very short exhausts on modern bikes. The added control of the ECU and fuel injection, along with the sensor control make this kind of thing a non-issue on modern bikes - so it is my understanding that the exhaust pulse and management of that for tuning purposes in modern bikes is not an issue worth addressing as it really is insignificant due to the above.

    If this was such a big issue the aftermarket exhaust industry and can industry would be non-existant. I know there is a lot of fashion and hype about that but in most cases a full exhaust will add hp without changing mixtures on a modern ECU bike. It of course changes the airflow and the tuning but the ECU accommodates for that appropriately in modern bikes. Maybe not bikes that are 15 or more years old but the R1200 for the most part (it is only my understanding) is not affected for mixture - It is affected and shows performance gains with better air flow (filters) =more oxygen and better exhaust flow = less back pressure more flow - easier to push that out the back end.

    Like you said - none of us really know unless we get the data on the specific bike and do the tests right... so it is cautioned speculation I think based on our combined years of experience... wow kind of scary that actually. But in the long run I think we are all pretty safe with these things - maybe not perfect but I think... safe. :1drink
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  18. roger 04 rt

    roger 04 rt Long timer

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    There must be some mid-range effects of intake and exhaust tuning on this bike. And it is certainly possible for tuning to effect the mid range (though admittedly I don't have any data on that effect on the R1150). I say that because the R1150RT and the R1150GS have much different intake tubes--for what reason other than tuning the intake?
    #18
  19. carlesonra

    carlesonra n00b

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    RogerRT
    Thanks for the post. My plugs are dual electrode which may be make a difference in read. That said, compared to your Autolite picture, my GS is showing lite grey even inside the plug, Based on the posts I have read here, I may be attempting to fix a normal burn as I have no spark knock or throttle issues with this machine; my old dirt bike days may be saying it is lean only in my mind. So, if it ain't broke don't fix it. The K&N may need another look though.

    Thanks to all for responding to my question.

    Carlesonra
    miscellaneous other motorbike
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  20. Marki_GSA

    Marki_GSA Long timer

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    If anyone is interested.

    Exhaust pulses are used to keep the fresh intake charge in the cylinder during the valve overlap (both intake and exhaust valves open at the same time). The reflected wave acts as a damn at the exhaust port and would be tuned to arrive in the mid to low rev, dependent on what your looking for and there are equations to work it out. In brief its longer header for lower RPM, shorter for higher RPM. Higher RPM offers less time for it to happen so is simply of less use if any there. It occurs when there is a change in pipe diameter or a sharp turn. It will never enter the cylinder itself and stop fuel air getting in simply because the port reflects it back. How much use it is depends on many other aspects of the engine tune. Decat headers for example often show an increase in the low-mid range power because of the different and smaller Y joint so a stronger pulse is sent back up. It also obviously offers less restriction in flow with no cat in line so pumping losses are reduced at high RPM.
    Intake length is partly about keeping the fuel in the inlet track. If you look at an engine with bellmouths (the intake pipes are simple bellmouths that exit in the airbox) on and look in while giving the throttle a good twist you will see a mist of fuel making its way out. Too short a track and the fuel can escape. As ever it isn't so simple though because there are pulsed involved here as well so a long intake track that will keep the fuel in at all times wont be the best for a high revving engine. Similar to the exhaust tuning longer is best for low-mid and short for high RPM.
    Aftermarket exhaust manufacturers exist because they are in part free from what a mass production design has to cope with. They can play to a point with the tuned length and general packaging to suit what a purchaser wants I.E race bike or slow plodder. Whether its better or worse for a particular person is dependent on them. They also dont have so many regulations to cope with such as they can sell an exhaust without a CAT where the main manufacturer cant.
    Both intake and exhaust tuning really do only offer small gains, even when tuned properly but they are noticeable to the butt dyno and a real dyno. As I said earlier though if not tuned properly they can make losses which is the opposite from what your actually trying to achieve. To get the best use from an exhaust and air filter change either a ECU fuel remap is required or something like a power commander fitted. There is a thread over on UKGsers with a company offering ECU remaps. There are dyno graphs posted that show even on a stock bike there are benefits to a remap showing useful gains never mind after component changes.
    #20