The Mechanic
Guest
The Lambda probe [one wire] oxygen sensor and HEGO (heated ex. gas oxygen sensor 3 plus wires) are usually referred to as the LAMBDa control circuit. This is a CLOSED circuit feedback system (lambda loop) in that the signal from the LAMBDA sensor in the exhaust can directly affect the fuel quantity injected. The ECU controls the amount of injected fuel by varying the injector pulse width (how long the injector is held open hence more or less fuel srayed) and subsequently combustion temperature. Too lean a mixture caused by insufficient ex. back pressure or an air leak equates to potential burnt valves.
Take the Lambda sensor out of the ECU information loop and the only thing the ECU can do is resort to random access of the fueling and ignition map to try and keep you the rider moving.
Faults that mainly cause problems to the LAMBDA sensor are:
1. Excessive heat from the down pipe and surrounding metalwork added to vibration, can make the sensor wires become work hardened, this affects the electrical resistance and subsequently the feedback to the daer old ECU. This is known as a slow lambda sensor-- it doesn't respond to temperature change quickly enough and hence causes indifferent fuelling when it should be more accurately controlled. Rough engine performance and stuttering. Where do BMW site the Lambda underneath the transmission and the bashplate does a good job of deflecting what little cooling air there is to help the wires. Sit idling or trickling in traffic too long and the sensor wires will be like their sitting next to a welders torch! Most car Lambda sensors at least receive a little more air than that, even in traffic.
2. Contamination from the exhaust gases can coat the sensor and reduce the reaction time. This sometimes referred to as a cool Lambda. Rule out anti-freeze, but consider fuel additives and silicone sealer as potential death to the sensor; along with many other foreign liquids and chemicals that seem to be gayly chucked in with abandon. Of course to much angine oil will also create its own problems.
Construction:
The LAMBDA sensor or probe (call it what you will) contains amongst other things ZIRCONIUM DIOXIDE (Zr02). This is applied as a ceramic and is housed in a gas permeable electrodes of PLATINUM, a further ceramic coating is applied to the side of the sensor exposed to the exhaust gases as a protection against residue from the combustion process. Not a fail safe!
Principle of operation:
At temperatures in excess of 300 degrees C, the ZIRCONIUM (sounds like some far off planet) DIOXIDE will conduct the oxygen ions. NOTE the sensor must not be subjected to temperatures above 850 degrees C otherwise damage may/will occur!
The sensor is designed to be responsive very closely to a LAMBDA value of ONE. As one electrode of the sensor is open to reference value of ATMOSPHERIC air, a greater quantity of oxygen ions will be present on this side. Due to ELECTROLYTIC action these ions permeate the electrode and migrate through the electrolyte (Zr02). This builds up a charge rather like a battery. The size of the charge is dependant on the OXYGEN percentage in the exhaust. A voltage of 400mV is the normal figure produced at a LAMBDA value of one.
The closely monitored CLOSED LOOP feedback of a system using LAMBDA sensing allows VERY accurate control of the engine fuelling. Close control of emissions is therefore possible.
What the f**c*s an ION?
Ions, this represents an electrically charged atom or group of atoms formed by the loss or gain of one or more electrons. Good innit.
Tip:
Whether a single wire sensor or HEGO (the GS has 3 wires so its a heated bugger, it will get hot without the engine running provided the ignitions on) should the wires be stiff and feel very unlike wires but mores like welding wire covered in plastic then get the thing replaced becausethe work hardened wires will give rise to high resistance for both types of sensors. Slow heat up if at all and distorted data signal- current.
Remember that no one rides around at idle, so checks at idle speed are non-sensical, and no one rides around flat out all day as some might lead you to believe; its for this reason that you should not leave the sensor out or disconnected. Those specialists that do give this instruction ( to leave out the sensor)want the ECU to be guided by their programme at some or all of the time, they know what they are doing with their kit but this does not mean it will be alright for other mods by other people.
I see from other threads that some GS owners have lost valves, but there is scant details as to tell tale signs before the fault, also no real info on previous mods or fettling.
Valve clearances set too tight will most certainly cause burning but that also manifests itself with bad running, starting and loss of performance which getrs worse. Air leaks in the exhaust system will cause lean running and air leaks in the front pipe to cylinder head will cause the exhaust gas temperature to soar way above the design limits for the valve, hance melt down/burning. An air leak at the inter-connecting link could produce this system.
My GS front pipes went so blue on the way back from collecting her new that when we stopped for food I nearly fainted with shock £9600 for cacky blue pipes takes me back to Bonneville days but they only just blued slightly on the first bend from the cylinder head. So I've made the decision to leave everything bog standard, so if mine go BMW will foot the bill.
I can hear the clank of spanners and the sound of rummaging for those discarded engine mangement components, yep and theres the rustle of warranty paper work being examined by some worried owners. Thinking of buying a second hand GS check it very carefully for signs of the dreaded finger trouble, TUNING!
See you on the road sometime guys and gals!
Take the Lambda sensor out of the ECU information loop and the only thing the ECU can do is resort to random access of the fueling and ignition map to try and keep you the rider moving.
Faults that mainly cause problems to the LAMBDA sensor are:
1. Excessive heat from the down pipe and surrounding metalwork added to vibration, can make the sensor wires become work hardened, this affects the electrical resistance and subsequently the feedback to the daer old ECU. This is known as a slow lambda sensor-- it doesn't respond to temperature change quickly enough and hence causes indifferent fuelling when it should be more accurately controlled. Rough engine performance and stuttering. Where do BMW site the Lambda underneath the transmission and the bashplate does a good job of deflecting what little cooling air there is to help the wires. Sit idling or trickling in traffic too long and the sensor wires will be like their sitting next to a welders torch! Most car Lambda sensors at least receive a little more air than that, even in traffic.
2. Contamination from the exhaust gases can coat the sensor and reduce the reaction time. This sometimes referred to as a cool Lambda. Rule out anti-freeze, but consider fuel additives and silicone sealer as potential death to the sensor; along with many other foreign liquids and chemicals that seem to be gayly chucked in with abandon. Of course to much angine oil will also create its own problems.
Construction:
The LAMBDA sensor or probe (call it what you will) contains amongst other things ZIRCONIUM DIOXIDE (Zr02). This is applied as a ceramic and is housed in a gas permeable electrodes of PLATINUM, a further ceramic coating is applied to the side of the sensor exposed to the exhaust gases as a protection against residue from the combustion process. Not a fail safe!
Principle of operation:
At temperatures in excess of 300 degrees C, the ZIRCONIUM (sounds like some far off planet) DIOXIDE will conduct the oxygen ions. NOTE the sensor must not be subjected to temperatures above 850 degrees C otherwise damage may/will occur!
The sensor is designed to be responsive very closely to a LAMBDA value of ONE. As one electrode of the sensor is open to reference value of ATMOSPHERIC air, a greater quantity of oxygen ions will be present on this side. Due to ELECTROLYTIC action these ions permeate the electrode and migrate through the electrolyte (Zr02). This builds up a charge rather like a battery. The size of the charge is dependant on the OXYGEN percentage in the exhaust. A voltage of 400mV is the normal figure produced at a LAMBDA value of one.
The closely monitored CLOSED LOOP feedback of a system using LAMBDA sensing allows VERY accurate control of the engine fuelling. Close control of emissions is therefore possible.
What the f**c*s an ION?
Ions, this represents an electrically charged atom or group of atoms formed by the loss or gain of one or more electrons. Good innit.
Tip:
Whether a single wire sensor or HEGO (the GS has 3 wires so its a heated bugger, it will get hot without the engine running provided the ignitions on) should the wires be stiff and feel very unlike wires but mores like welding wire covered in plastic then get the thing replaced becausethe work hardened wires will give rise to high resistance for both types of sensors. Slow heat up if at all and distorted data signal- current.
Remember that no one rides around at idle, so checks at idle speed are non-sensical, and no one rides around flat out all day as some might lead you to believe; its for this reason that you should not leave the sensor out or disconnected. Those specialists that do give this instruction ( to leave out the sensor)want the ECU to be guided by their programme at some or all of the time, they know what they are doing with their kit but this does not mean it will be alright for other mods by other people.
I see from other threads that some GS owners have lost valves, but there is scant details as to tell tale signs before the fault, also no real info on previous mods or fettling.
Valve clearances set too tight will most certainly cause burning but that also manifests itself with bad running, starting and loss of performance which getrs worse. Air leaks in the exhaust system will cause lean running and air leaks in the front pipe to cylinder head will cause the exhaust gas temperature to soar way above the design limits for the valve, hance melt down/burning. An air leak at the inter-connecting link could produce this system.
My GS front pipes went so blue on the way back from collecting her new that when we stopped for food I nearly fainted with shock £9600 for cacky blue pipes takes me back to Bonneville days but they only just blued slightly on the first bend from the cylinder head. So I've made the decision to leave everything bog standard, so if mine go BMW will foot the bill.
I can hear the clank of spanners and the sound of rummaging for those discarded engine mangement components, yep and theres the rustle of warranty paper work being examined by some worried owners. Thinking of buying a second hand GS check it very carefully for signs of the dreaded finger trouble, TUNING!
See you on the road sometime guys and gals!
