Loops

[Justin]

Can someone give me a basic explination of closed loop an open loop?

i think that i know the car idles at closed loop and the AFR is like 17:1... that's about all i know

why, what, and... thanks

 

[Anh]

Closed loop is when the ECU adjusts the fuelling based on the readings of the 02 sensor.

Open loop is when at WOT the ECU just fuels the engine based on engine load and RPM.

 

[Justin]

so open loop is ONLY at wot?

and closed loop is always, except wot?



emanage/afc/things like that can't modify closed loop, is that correct?

 

[Anh]

Not quite, open loop happens when the engine is cold, or when at above 70-80% throttle.

Not too sure about this, all I know is emanage and afc alters the signals from the AFM which affects fuel and timing, but at the same time closed loop mode naturally re-adjusts only the fuel.

 

[GrimJack]

Look at it this way.

Closed loop is when the ECU is paying attention to the O2 sensor. Open loop is when it's not.

Figuring out when the ECU is running in one mode or another is much more interesting.

 

[flubyux2]

closed loop means that the electrical circuit is completed, so voltage can fluctuate up and down. it means that the cycle can complete itself to ground.

open lop means that the electrical circuit is INcomplete and there is a break in it. the voltage cant fluctuate and has no path to ground in order to complete itself.

in a linear mode, close loop will show voltage readings fluctuating up and down. in a graph mode, closed loop will show up as a sin wave as the voltage goes up and down as time progresses.

in linear mod, open loop will show as a constant voltage and will not fluctuate up and down. when in graph mode, open loop will show as a constant line above the x-axis and will not drop down.