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+--- Thread: oxigen sensor tutorial (/showthread.php?tid=4980)
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oxigen sensor tutorial - max - 03-23-2019
Very in-depth explanation about the function of an oxigen sensor in an engine, long and short term fuel trims and reset purpose.
https://www.youtube.com/watch?v=oRX2V6_a3dc
This video finally made clear to me how an oxigen sensor works and why it's output produces a variable wave instead of a straight line graph.
In short; the sensor operates within a narrow band and measures the exhaust gas, tells the ecm if the value is too rich or too lean and tries to keep the optimum stoichiometric air/fuel ratio at 14:1.
The ecm then adjusts the short term a/f ratio to maintain this value which is important for the functioning of the catalytic converter.
Over time the ecm learns this trend and produces an internal "map" of values for various engine speeds and other inputs, this is called "long term fuel trim" and is stored in memory to provide a base line for a/f control.
If there is a fault in the fuel system ( vacuum leak ) the ecm re-learns the "map" and changes some values in it, once the fault has been repaired these "wrong" values need to be reset by disconnecting the battery for 10 minutes which does a reset and then re learns a new set over time.( not sure about this but a good possibility )
This may be important info for the ones that remove the battery from the bike for storage!
As i am not knowledgeable enough to give any advice, may well be wrong in what i just stated and may not relate to our bikes i want you to not rely on my explanation, however there may be some info here that explains IF there is some unexplainable subtle behavior change with battery replacement.
Not trying to panic anyone, nothing is wrong, just some careful subtle advice with a little back ground.
If there is a better or more correct explanation out there i am sure we would like to hear it.
RE: oxigen sensor tutorial - GoldOxide_imp - 03-23-2019
Sure, if the "user" map is not stored in non-volatile memory (I do not know if it is or is not), then when the battery is restored, factory settings are probably used as the basis of the re-learn sequence and subsequent new "user" map.
RE: oxigen sensor tutorial - Toro5xi_imp - 03-23-2019
It’s not only the fuel trims which are lost but also settings related to the IAC, Idle Air Control. I have changed battery’s on cars and they will stall or nearly stall until the idle speed settings are relearned. In the dealer ship we would keep the ECM powered via the DLC, data link connector, to avoid losing settings. Another method is to use alligator clips and an external battery connected to the battery cables when changing out the battery.
The long term fuel trim is accessed via the scan tool and a good indicator as to the health of the engine and engine management systems. The short term fuel trim is designed to switch from lean, low voltage, to rich, high voltage as measured by the O2 sensor so not usually used for diagnostics other than to verify the system is switching constantly from slightly rich to slightly lean as you mentioned for the catalytic converters to eliminate hydrocarbons, carbon monoxide and nitric oxide.
As you mentioned the long term fuel trim percent indicates if the system is adding or subtracting from the hard coded fuel maps to compensate for dirty air cleaners, weak fuel pressure, manifold leak etc. Typically if that percent exceeds 10 percent in either direction the check engine light is set and a trouble code is stored.
Finding and correcting diagnostic codes is not always easy as the code will say if the engine is running lean or rich but the technician has to often eliminate many different possibilities before finding the root cause. That being said I enjoyed driveability work.
RE: oxigen sensor tutorial - jimgl3_imp - 03-23-2019
so would it just be wishful thinking to think one could do a tsr and full exhaust with o2 sensor and reset the ecm by battery disconnect and it would relearn with the new intake and exhaust, eliminating the need for dynojet or similar module?
RE: oxigen sensor tutorial - Toro5xi_imp - 03-24-2019
That is a good question and I don’t have enough knowledge of emissions work on motorcycles to give a comprehensive answer. The O2 sensor only directs the fuel injector pulse width when the car or bike is running in closed loop operation. I have been told on motorcycles that they operate in closed loop for a small percentage of time in comparison to automobiles, which is more my background.
Just to add more background and indicate why custom fuel maps are designed is that maximum power is achieved at richer ratios than stochiometric or 14.7 to 1. When custom fuel maps are uploaded the O2 sensor must be disabled or the computer will try and adjust the fuel ratio back to stochiometric in essence disabling the custom fuel map.
RE: oxigen sensor tutorial - max - 03-24-2019
Toro thanks for all your valuable input, i was hoping guys like you would add to the story, i have also heard the ox sensor is only used at low speed.
I am considering mounting a small voltmeter on the bike so i can see the output of the o2 sensor and see if that is true and having a look at providing the ecm with something like 0.7 volts ( middle of the range ) to simulate the sensor and reduce/eliminate the slightly hesitant behavior of the otherwise lovely engine.
Main reason for posting was the insight it gave me in the workings of the fuel trims and i thought some of us may appreciate the video i stumbled across, any thoughts?
RE: oxigen sensor tutorial - Toro5xi_imp - 03-24-2019
Hi Max
The voltage meter hooked up to the O2 sensor is a great idea. There is 1 wire that you can back probe which sends the voltage signal to the ECM that you want to tap into. The wiring diagram will tell you which wire you want to back probe.
I thought the fueling on my 2014 CB was very good so never really dug into it. You sound like you are interested in this stuff. It might be worth looking at the calibration of the TPS, throttle position sensor. I am not specifically aware of it on the CB but I had a Bandit where it was possible to change the position of the TPS so the ECM thought the throttle was open more than it actually was so more fuel was added.
This stuff makes logical sense if you just understand the ECM is taking input from the various sensors, then references a vlook up table to see how long the injector needs to be on to provide the proper quantity of fuel to obtain the 14.7 to 1 ratio we have talked about. We used to put holes in the vacuum hose running to the MAP sensor, manifold absolute pressure, so the ECM thought the engine was under a greater load than it actually was and add more fuel to richen the mixture.
Where it gets tough is that some cars use a speed density system, some rely on the mass air flow sensor, and they all use different sensors. Without access to factory flowcharts or other documentation it is difficult to know where to start. I am sure it has gotten more complicated over the years but it is very logical from a cause end effect stand point. For instance at start up the ECM needs to know the temperature of the air to compute or infer the air density. Denser air needs more fuel to obtain the proper ratio we have been talking about. If the ECT, engine coolant sensor, has failed or is no longer calibrated properly than the ECM will use the wrong air mass quantity and thus add the wrong quantity of fuel.
Sorry for the long winded post I guess I am just trying to encourage anyone who is interested in this stuff not to be intimidated. Once you understand the basics it really makes a lot of sense.
RE: oxigen sensor tutorial - dave - 03-25-2019
Thank you Max.
RE: oxigen sensor tutorial - max - 03-26-2019
Cheers Dave,
(03-24-2019, 07:20 AM)Toro5xi_imp Wrote: Hi Max
The voltage meter hooked up to the O2 sensor is a great idea. There is 1 wire that you can back probe which sends the voltage signal to the ECM that you want to tap into. The wiring diagram will tell you which wire you want to back probe.
I thought the fueling on my 2014 CB was very good so never really dug into it. You sound like you are interested in this stuff. It might be worth looking at the calibration of the TPS, throttle position sensor. I am not specifically aware of it on the CB but I had a Bandit where it was possible to change the position of the TPS so the ECM thought the throttle was open more than it actually was so more fuel was added.
This stuff makes logical sense if you just understand the ECM is taking input from the various sensors, then references a vlook up table to see how long the injector needs to be on to provide the proper quantity of fuel to obtain the 14.7 to 1 ratio we have talked about. We used to put holes in the vacuum hose running to the MAP sensor, manifold absolute pressure, so the ECM thought the engine was under a greater load than it actually was and add more fuel to richen the mixture.
Where it gets tough is that some cars use a speed density system, some rely on the mass air flow sensor, and they all use different sensors. Without access to factory flowcharts or other documentation it is difficult to know where to start. I am sure it has gotten more complicated over the years but it is very logical from a cause end effect stand point. For instance at start up the ECM needs to know the temperature of the air to compute or infer the air density. Denser air needs more fuel to obtain the proper ratio we have been talking about. If the ECT, engine coolant sensor, has failed or is no longer calibrated properly than the ECM will use the wrong air mass quantity and thus add the wrong quantity of fuel.
Sorry for the long winded post I guess I am just trying to encourage anyone who is interested in this stuff not to be intimidated. Once you understand the basics it really makes a lot of sense.
I thought the fueling on my 2014 CB was very good so never really dug into it. You sound like you are interested in this stuff. It might be worth looking at the calibration of the TPS, throttle position sensor. I am not specifically aware of it on the CB but I had a Bandit where it was possible to change the position of the TPS so the ECM thought the throttle was open more than it actually was so more fuel was added.
Have seen video's of someone doing a similar thing to a ktm, increase the tps "idle voltage" by 0.2 volt and get more grunt, not sure if that bike had an o2 sensor or not that would fight that situation, actually not looking for more HP on this bike, i actually "tootle" around more than anything but i can feel a need to improve the slight hunting it has between 2000 and 3000 rpm which would indicate the o2 sensor playing a part in that range and many have had success with their sensor eliminators.
Although i can put one on and have temporarily done so with the desired effect i am cautious to what might happen with the cat converter and the o2 sensor itself, so i like to find another way to stabilise the ecm fuel control whilst maintaining all inputs in line.
To do this i need a better understanding of what the consequences are, hence the video that i thought might be handy for others as well
(03-24-2019, 07:20 AM)Toro5xi_imp Wrote: Hi Max
The voltage meter hooked up to the O2 sensor is a great idea. There is 1 wire that you can back probe which sends the voltage signal to the ECM that you want to tap into. The wiring diagram will tell you which wire you want to back probe.
I thought the fueling on my 2014 CB was very good so never really dug into it. You sound like you are interested in this stuff. It might be worth looking at the calibration of the TPS, throttle position sensor. I am not specifically aware of it on the CB but I had a Bandit where it was possible to change the position of the TPS so the ECM thought the throttle was open more than it actually was so more fuel was added.
This stuff makes logical sense if you just understand the ECM is taking input from the various sensors, then references a vlook up table to see how long the injector needs to be on to provide the proper quantity of fuel to obtain the 14.7 to 1 ratio we have talked about. We used to put holes in the vacuum hose running to the MAP sensor, manifold absolute pressure, so the ECM thought the engine was under a greater load than it actually was and add more fuel to richen the mixture.
Where it gets tough is that some cars use a speed density system, some rely on the mass air flow sensor, and they all use different sensors. Without access to factory flowcharts or other documentation it is difficult to know where to start. I am sure it has gotten more complicated over the years but it is very logical from a cause end effect stand point. For instance at start up the ECM needs to know the temperature of the air to compute or infer the air density. Denser air needs more fuel to obtain the proper ratio we have been talking about. If the ECT, engine coolant sensor, has failed or is no longer calibrated properly than the ECM will use the wrong air mass quantity and thus add the wrong quantity of fuel.
Sorry for the long winded post I guess I am just trying to encourage anyone who is interested in this stuff not to be intimidated. Once you understand the basics it really makes a lot of sense.
Don't think it was long winded, i am very happy to hear other's opinion especially coming from a knowledgeable source like the settings for the tps etc, all this helps me to complete the puzzle, i have done some programming and know some basics so i can follow all this theory, but i am not "fluent" in programming like csory is, fortunately i do have a wide background in electronics and some good friends are a great resource which enables me to evaluate some pitfalls ahead of time
One day i wondered how a micro processor worked and with the help of a friend made one that you could step the clock step by step with a push button, you could see the bus and adress lines change with every push, fascinating for me to watch it add 2 and 3 and display 5 in binary.
Very basic for some but i found it interesting and it helped me get an insight in some of it, like playing with electronic lego.
very interesting to hear your input
RE: oxigen sensor tutorial - Houtman_imp - 03-30-2019
On quick and only question : can you eliminate the O2 sensor when installing a 4 into 4 Pipe Master ? and will the engine run "perfect "