Closed Loop, Open Loop operation

I remember reading that someone stated that idling was a closed loop operation like WOT. I remember in previous trouble shooting that if I disconnected my AFM that it would idle, unless I touched the throttle leading me to believe that this is true.

My concern is that my AFM maybe bad, and that if disconnecting my AFM and my car idles proper, (which it doesn't do now), then I would assume that my AFM is giving a bad signal leading to my running problems.

I have the BGB and plan to test the AFM, but I thought this might be a simple test for some who may not have purchased the BGBs yet. Plus I'm a bit curious to understand the ECU operations as well.

I am pretty sure cold start works off of maps, but I'm not sure that normal idle does. When monitoring A/F's at idle, I see the normal fluctuation up and down. From memory, it will settle out at ~14.7:1 once it decides where that is. After a blip in the throttle, it will readjust until it figures out where 14.7 is again.

GT4CE":3qmyetz1 said:

I remember reading that someone stated that idling was a closed loop operation like WOT.

Click to expand...

I think we should clear up terminology a little.

Closed Loop = Feedback Control System. (The O2 sensor is a common feedback element.)
Open Loop = No-Feedback Control System.

WOT is Open Loop.
My experience is that idle is Closed Loop, like Chris mentioned.

___Scott___":1d6rsegg said:

GT4CE":1d6rsegg said:

I remember reading that someone stated that idling was a closed loop operation like WOT.

Click to expand...

I think we should clear up terminology a little.

Closed Loop = Feedback Control System. (The O2 sensor is a common feedback element.)
Open Loop = No-Feedback Control System.

WOT is Open Loop.
My experience is that idle is Closed Loop, like Chris mentioned.

Click to expand...

Yes, this is correct.

Thanks I had a feeling I got that one backwards, physics doesn't have situations where things don't count unless you can calculate that the effect is negligible, so it doesn't stick in my head.

Take a few classes on control theory. It'll stick, I guarantee!

The general control loop diagram will become burned in your brain: