The only output that hasn't been explained yet is the IAC.
I think that this is coming out perfect. Very simple and basic for the beginner so you don't feel overwhelmed the first time you look at the datalog like I did!...lol
Almost ready to datalog?
IAC...as it says....IDLE AIR CONTROL
When you make a mixture more rich or lean it effects the idle. By opening the throttle plates, the idle can go up and down if you add more air in, or take air out of the mixture.
The car has to idle at a particular RPM under numerous conditions. The IAC does that.
For example, if your in neutral, the load on the engine is zero and the idle will be what it is.
What happens when you turn on the air conditioning? The computer know the idle should be say 1000 RPM. So it makes the idle 1000 RPM. When you go from Neutral to gear, the motor steps down again, so the IAC brings the idle back UP to where it's supposed to be.
How does it do that? Well picture a screw inside a pipe. The screw has a cone shaped head called a Pintle. The pintle fits inside the pipe which is also cone shaped on the inside. So the screw goes in and out of this cone shaped tapered recess in the pipe, depending on the idle.
So the ECU is looking at the INPUTS, sensors, and the RPM and saying......HMMM....the RPMs are high/low based on the input of the sensors I need to add/subtract air.
There is a hole in the throttle body which is opened or closed by the IAC moving in or out. When the IAC retracts the pintle the hole is opened, allowing more air into the system, raising the RPMS. When it is closed, the mixture is richer.
So it, the ECU, backs out, or runs in, the IAC until the idle meets the pre programmed designated idle. Once there, it stops.