O2 Sensor Open/Close Loop

[kleenair at ix.netcom.com]

tom cloud wrote:
> 


Hi,

This is some more info about open/closed loop and A/F ratio:

The target A/F ratio during WOT can varry from engine to engine.  More specifically, 
it is related to fuel pressure, fuel injector nozzle design, and injector location.  
The objective is to deliver the correct amount of fuel in fine particles to the 
combustion chamber.  So theoredically, if all the fuel was vaporized, you would not 
need a WOT enrichment.  Therefore, on multi port fuel injection systems with higher 
pressures, the WOT A/F is very close to stoichiometric.  In fact, some newer vehicles 
(1996) do not go to open loop during WOT!  By contrast, when you consider a throttle 
body injection setup (or a carburetor), the fuel has many opportunities to form as 
dropplets on intake manifold walls.  Therefore, you add the extra fuel to compensate.
So to make a long story short, depending on your fuel system, both the target A/F, 
and the Open/ closed threshold varry.

Mazda Ebrahimi