Originally Posted by NJ-Brett
Some systems have dual throttles, one cable operated, one stepper motor operated, both have position sensors.
I am not sure why they do it, maybe its the CV carb of fuel injection.
Also, closed loop usualy is the system looking at the OXY sensor, it always looks at all the others.
Most bikes are only closed loop over a small range, mid throttle, mid rpm's, where the EPA measures.
Most bikes also do not have idle speed control, but have a way to bump the idle up on cold start.
I am very interested in learning more about the Honda systems.
The IAC is a stepper motor that allows extra air into the engine to control the idle speed. The throttle closes sightly further which decrease emissions on decel. When the RPM drops low enough the IAC takes over to control the idle speed. There is a minamum air flow spec that the throttle stop screw is adjustent determines. It is preset by the factory and painted so tampering can be determined.
2013 models have different emission standards they need to meet. That is why the stock muffler contains a catalitic converter for example.
In open loop it watches the TPS, MAP, CKS, IAT and the ECT sensors mainly. It uses these values to determine what base programing cells in the computer to use.
In closed loop it moniters the O2 sensor also, using it to provide the information the computer needs to achieve the desired air fuel/ratios. The adjustment to fuel control are done by the short term adaptive memory. The long term adaptive memory watchs the trends and adjustments the short term memory makes and then adjusts it's values so the short term memory stays near the center of its adjustment range. The long term memory stores this so it's dialed for the next time it goes into closed loop. The short and long term memory has the ability to add or remove the amount fuel the engine sees by adjusting fuel injector pulse width as needed.
I think closed loop operation has been increased for 2013. It probably handles hot idle and 0% to about 50% throttle openings. It won't go into closed loop until the OS sensor reaches the proper temperature. There are some other perimeters involved also.
Cold operation and 50%+ throttle operation is done in open loop on base programing.
The computer has multiple memory cells it uses for both closed and open loop operation. These cells store the base programing for open loop and the adjusted programing for closed loop operation. There is also a limp in mode if a sensor the open loop needs to moniter fails. Sometime limp in mode equals tennis shoe mode because it lost the crank sensor signal or such.
Tennis shoe mode means your walking. Limp in mode means it will get you to home but thats about it.
Hope that helps. I'm done for know...