At idle RPM's WB AFR shows about 12.6 while BLM's show about 136 open loop. What should I believe? Does learn mode not work right open loop? When I rev it a bit it goes closed loop and AFR goes closer to 14 but my nasty surging RMP comes back too, that's why open loop idle.

 

Read and re-read the stickies up top.

Dont trust any correction based off o2's until closed loop is achieved and under normal conditions, not where u rev it and it fades back and forth from open to closed.

Wideband reading rich would be normal for open loop at temps under normal operating.

Little info on what your doing might help too.

later
Jeremy

 

Thanks for the reply. It's not fading in and out of closed loop when I do this. It's at full temp too...................I am and have been having surging issues and trying to get to the bottom of it. Set it for open loop idle to try and help with this which it did but once it's above the open loop RPM range it goes right back to surging. I just got the WB last week so now I have more info. From what I understand open loop the BLM's should read 128 weather their stoich or not? WB says their rich and ECM says lean, that's what brought up my question. When it does it's surging thing (closed loop) the WB swings with the surge. It does it with the IAC closed and disconnected and with the VE 1 cells set to the same value in the range. Checked for vacuum leaks again for the millionth time, nothing. I thought this may look like something common to people on here and they may be able to help. I think I'm going to replace the NB O2 and see what happens.

 

One thing to remember is that in closed loop the ECM targets an O2 voltage, not an AFR. The actual AFR can be changed by changing the O2 windows.

As for the surging it is probably too much proportional gain.

RBob.

 

Just read your article. http://www.diy-efi.org/gmecm/papers/747fuel.txt
Thanks, this is the kind of stuff I think I need to figure this out!!!
Good stuff and explains it very well, I just need to digest it I think. One thing that did stick out though was this.

"It is important to realise that it takes a finite amount of time for a
change in the bpw to be reflected in the O2 sensor reading. This time
frame is referred to as the 'transport delay'."
Would this be the same thing as "Prop term duration O2 error"?

Reason being is my O2 (heated) is far down the exhaust. Could transport delay need to be adjusted to copensate for this extra distance between the engine and O2?

 

Moving the O2 sensor location affects the INT delay vs airflow parameter.

Included in the transport delay is the time from a change in commanded injector PW, engine rotation until that injector pulse is generated, then induction into the cylinder, compression and ignition, then exhausting that charge out the exhaust port.

This is followed by the delay from the exhaust port until the burnt gases hit the O2 sensor and the time for the O2 sensor to react.

RBob.

 

When I change the prop gains parameters I get a O2 error light. Do I need to change the O2 error boundries?

 

OK here are the adjustments I've made so far this afternoon. First I manually lowered the VE-1 values in the idle range to lean it out closer to 14.7. This seems to keep the O2 light off. Multiplies INT delay vs air flow by 3. Cut idle prop gains by half. Cut prop gain vs slow O2 by half. Cut prop gains vs air flow by half. All of this seems to have helped with the surging quite a bit, I haven't driven it yet. May just need some fine tuning. Now it's back to adjusting the VE-1 fuel table. Which brings me back to my original question/ concern. BLM's are reading lean while WB says rich. Untill now what I've done is log data win aldl and use aldl to bin to adjust with some smoothing. If I understand this right with the BLM's lean aldl to bin will adjust fuel richer than it already is.
Suggestions?
I do appreciate the help!!

 

If the BLM's are less then 128, then the VE table is rich (so to speak).

RBob.