I think I understand what you are saying Scott, But you are not being simple enough for this dummy.
What sensors decide this? If the after market fuel controllers are able to change the status, then isn't it fooling the computer into thinking the o2's are sensing something else?
What sensors beside the o2's feed the computer for fuel adjustment? If an after market fuel controller can cause the computer to add more fuel, then the computer is capable of adding more fuel.
If it is getting this info from the o2's alone, then isn't it reasonable to think that if you back out the o2's from the exhaust stream a tad or put a variable resister in the o2 line, couldn't you do the same thing?
I don't want to cause confusion or you to think I doubt your word, I am just trying to understand where the computer gets its information from.
1st question, yes. On a Star bike with an AIS
the computer may be expecting to see an O2 voltage averaging say around 0.2 during idle and light cruise which is very lean but okay because of the air coming from the AIS. If the fuel controller is made to work without the AIS then it will adjust fuel flow so the O2 reads around 0.45 volt which is a 14.7:1 AFR and send a different voltage reading (the one it's expecting) to the stock computer.
The other sensors are the MAP
(manifold absolute pressure) sensor, engine temperature, atmospheric pressure, air temperature, engine speed and the TPS
. The input from the temperature sensors is obvious - the computer needs to know the intake air temperature and the engine temperature.
The computer FI system sensors convert atmospheric pressure and manifold pressure to a voltage signal. Everything is measured in absolute pressure which at sea level averages 29.92 inches of mercury. In the simplest terms the computer compares the difference between the surrounding air pressure and the pressure in the manifold and makes a determination about engine load. The TPS plays a part also but let's take an example of cruising on the highway with the throttle lock set. Without the MAP sensor on the FI system the computer wouldn't be able to sense more load when the bike starts climbing a hill (same throttle setting, more load and the pressure difference increases). The equivalent on the CV carbureted bikes is the slide diaphram.
A resistor in the O2 circuits. That can be done and has been done with the VStar 950's and 1300's because they run lousy with aftermarket filters and pipes. Why anyone would want to change those bikes is beyond me. The stock exhaust on the 950 is pretty mean sounding already and the 1300 will already outrun the Roadie and maybe the 950 as well.
What you would have to do is measure the O2 sensor output with the AIS connected. The sensor is sending voltage readings at the rate of about 8 times/second and they're always above or below the desired reading. If the reading is very low then there won't be enough room to lower it with a resistor. The idea is to provide a resistor that lowers the voltage enough so that when the computer gets it it richens the mixture enough so that the voltage from the O2 sensor before the resistor is around 0.45 volt (14.7:1 AFR). This may be exactly what some of the aftermarket fuel controllers do, I don't know.
As far as acceleration mode goes the O2 sensor is ignored anyway but with the volumetric efficiency increased the stock computer may be approaching the limits of its map.
I'm going to stop here. Let me know if I was vague in some area.