Lambda Sensor.
Hi, Jimb.
No the Lambda doesn't supply a resistance it provides a voltage reading for the ECU to monitor.
Anything is possible, the potentiometer tricks the ECU into thinking that the (now disconnected) Lambda Sensor is producing one constant and unvarying voltage signal....until human intervention (you alter the potentiometer setting).
I personally would not go this route, instead prefering to fit a potentimeter into the fueling circuit (which is exactly what a Power Commander does) this is far safer as the Lambda Sensor will communicate with the ECU and allow some variation in engine fueling should a mixture running fault be detected, i.e. running too lean.
If you were to measure the Pulse width.....the length of time the fuel injector is powered up....you would soon see that by altering the pulse width, the amount of fuel injected can be controlled.
This means that the longer the injector is held open the more fuel is allowed into the inlet tract, whilst fairly obviously the shorter the open period the smaler the quantity of fuel etc etc.
HOWEVER..... the Lambda Sensor will be monitoring the oxygen content in the exhaust gases and communicating this fact by a voltage generated by chemical reaction within the Sensor. Consequently the ECU will still try to control the fueling to maintain a contant voltage signal from the Lambda Sensor.
This voltage signal is equated to a mixture level. The ideal chemically correct fuel to air ratio is 14.7:1 (14.7 parts air to 1 part fuel....at sea level) It just so happens that 14.7 = air pressure at sea level which also = 1 bar. The Lambda equivalent to this converts to 1 (number one) this then means that with a reading of less than 1 the mixture is rich and more than 1 then the mixture is weak.
Example: reading is 1.23 = weak mixture.
reading is 0.98 = rich mixture.
The ECU will receive signals from a 'good' Lambda Sensor that constantly vary or alternate from 0.98 to 1.01 approximately (they all vary to some extent due to mass production variations).
So ther you are....by the way my partners stripping wall paper from the kitchen so I'm keeping well out of the way as I can't stand DIY decorating, she says she wants to do it so ..easy life!
Back to the plot, why do you want to fit a potentiometer to your bike?
If you are experimenting then be careful as it would be far to easy to go roaring off up the road only to frazzle a piston or pistons due to an over sight.
The Lambda Sensor on your bike is heated by a current to enable it to reach its operating temp, quicker. This will get 'bloody hot' so if as you imply you want to attach it to the catalytic convertor but not have it read exhaust gas ( blanking plug in the hole job) then the ECU will receive insufficient data and probably select a limp home fueling table which will not produce the effect you are tryong to achieve.
Here a trick that I have used to great effect on electronic engine management systems that will extract a little more performance.
By fitting a resistor into the engine temperature circuit it is possible to trick the ECU into thinking its powering an engine that is constantly not hot enough, so it provides a richer mixture...this obviously affects fuel consumption some what.. as the ECU thinks the engine is still warming up, but thats where the Lambda Sensor trips up this idea. But the ECU will still supply an increased pulse width to the injectors for the richer mixture that a cool engine requires. Its a kind of win win loose situation.
Playing with the pulse width is what most 'power chips' do to some extent, whereas some alter the ignition map as well.
You could fit larger injectors and play around with fuel line pressures, but this would be expensive and require unlimted access to a rolling road.
Not many people have twigged this but the GS's air inlet pipe is a mini ram air and if you were to make this air pipe larger and combine it with a richer fuel supply then as speed increased so would the ram air effect which would boost power perhaps by 8-10 bhp depending upon engine condition and set up...ever the optimist I am....
So now we either have total confusion or complete understanding
and I hope that your question is answered.
If you want to proceed with your mods, you can leave the Lambda Sensor in place, just disconnect the wirng loom beneath the fuel tank and fit what ever to this end of the loom.
Beware my motto, below. There have been many good engines built by tuners that made it no further than the dyno. Just one or two degrees of ignition alteration at max rpm is all thats needed to total an engines top end (piston crowns) and just a tad too lean to melt piston ring land edges (one side of the piston crown usually furthest away from the spark plug)...!
