o2 sensor limits and open loop

[Rev]

o2 nb sensor limits and open loop

I read that some ecus go to open loop when the o2 sensor reaches its reliable limits.
Now as many will know typically narrow band o2 is accurate from 14 afr to 15.2 afr outside this perculiar things happen, variations on too rich and too lean also temp dependant .

So at what o2 afr does the starlet ecu go to open loop ?
and at what o2 temperature does the ecu go to open loop?

I suspect these figures may be slightly different for earlier and later ecus ?
Appreciate any help at all.

 

[Rev]

Any ideas?

 

[dac69er]

you mean closed loop? will only be on idle and cruising situations.

i would assume it would look at the coolant temp sensor, when it can see the engine is up to temp it will use the reading from the o2 sensor. as for the temperature, its righ near the turbo outlet so it will be up to temperature pretty quickly.

 

[weeJohn]

The sensor wont read unless its warm enough, on cruise, idle and start up sometimes this happens with 1 wire sensors. The 4 wire sensors have their own heater to help prevent this happening, 4EFTE engines didnt get this but.

 

[Rev]

Thanks Dac but I do mean open loop. My safc2 high map is very different to the low map so when I go to open loop ( high map ) I can feel a big difference.
eg when I hit 0psi the ecu obviously goes to open loop which is usually at 2000 rpm.

@weeJohn seems to happen after warm up I have a problem at below 870rpm usually in very hot weather it is a revs dropping thing especially with a/c I know their are various causes of this but was wanting to eliminate the o2 behavior with large injectors as others haven't been successful. I am thinking if the engine goes to high map at say 800rpm it would have heaps too much fuel which may be contributing to the revs drop?

 

[dac69er]

im a bit confused? closed loop is when all sensors are within range and the ecu controls everything based on the sensor readings. open loop is when you are outside those set limits so the ecu assumes certain things and works off the predefined maps in the ecu.

surely your high and low map will just be switched by the tps? so you assentially have an idle map and a driving map as the tps is only on or off?

if all you have as an safc and your revs are dropping, i would very much doubt that is the issue.

 

[Rev]

Closed loop with sensors But when I cold start with single wire o2 I think weeJohn is suggesting it is open loop how long does it usually take to get the o2 up to temperature?

Re safc2
Normally the safc high low maps are supposed to match down low so as you say its usually not the safc but my tuner only did above 3000 rpm properly. Because the high map was so rich I thought it may be overfueling in some situations.

Idle can get really rough under a/c load and in the heat so if its not the o2 triggering overfueling at high temp as shown below do you think it may be the temp sensor taking out too much fuel at hot low revs? Now I tried adjusting fuel ( and leaned High map ) and can get improvement but never enough to stop revs dropping as the engine gets hotter and hotter while idling under load.. I should mention when the car idles up when ac turns on it revs up for 1 sec but after drops lower with the ac load so the idle up is not lfting the revs back to normal idle range.

1500deg F is 815deg C

 

[Rev]

Short update -
I found I can elimate the drop in revs at start up by increasing the high map fuel.
When the car starts the single wire 02 sensor is cold so is in Open Loop ( uses SAFC2 high map only ) this is before it gets hot enough and switches to closed loop ( which uses the low map at idle ) .
I had the High map quiet lean ( -33% ) which is why the revs were dropping, it may also be related to over advancing timing making matters worse. Not sure yet if I have hit the fuel limit or timing limit for the ecu .