What does open/closed loop mean ?

open loop:

INPUT>>>>FUNCTION>>>>OUTPUT

Closed loop uses feedback from output to adjust the function/input.

example: a lambda sensor altering fuel/air ratio based on oxygen content in exhaust.

open loop it doesnt make adjustments based on AFR i think.

So it runs open loop until the engine is up to temp then switches to closed loop

[Edited on 5/6/09 by cd.thomson]

Closed loop is when the wideband controller is adjusting the mixture, when set to open loop it is disabled, it can be set to goopen loop above certain revs or boost to make sure it is not able to go to weak.
Paul.

Closed loop uses the O2 signal to put a correction factor on the amount of injected fuel to try to make the exhaust gas optimal. (gEGO)

Open loop just uses the map to define the quantity of fuel going into the engine and doesn't use the O2 signal to alter fueling.

Paul.