Commanded AFR vs. Actual AFR

[txoutlaw]

I know this has probably been covered before, but WTF do we command an AFR for if you still have to fine tune LTFT's . I guess what I'm asking is there something that we have all missed here that would make tuning easier, or is this something that the factory guys did to make things more difficult!

I know that you have to enter the correct numbers for displacement (if you bored or stroked youre yore combo). But this just makes me wonder if there is something that we have all missed in the tuning aspect.

Could this problem be simply be remidied by using wide band O2's in place of the factory ones! I'm still learning here so dont get pissed at me yet!! I know some guys (including soundengineer) have put WB O2's in their car for logging purposes, but can this be done for the both the ECM and the VSM suite to use simultaniously, therefore eliminating the need for all the extra BS we have to do right now!

If i missed a post on one of these issues point me to it, if not help me understand this a little more clearly!!

[sgarnett]

Could this problem be simply be remidied by using wide band O2's in place of the factory ones! I'm still learning here so dont get pissed at me yet!! I know some guys (including soundengineer) have put WB O2's in their car for logging purposes, but can this be done for the both the ECM and the VSM suite to use simultaniously, therefore eliminating the need for all the extra BS we have to do right now!

As you guessed, part of the problem is that the stock sensors are only accurate at 14.6. They can't tell how far away from that you are, only that you are rich or lean.

Even if you installed a wideband sensor and the PCM knew what to do with it, the sensors simply don't respond fast enough to support WOT closed-loop operation.

[WS6FirebirdTA00]

scott uses the WB for a narrowband output, the computer isnt reading the actual afr. you command an afr and based on your VE is knows how to command it. so if it is off then the whole afr is off. you can command 14.7 on my car and your car but how will the computer tell how to get it to 14.7? through the VE table is how, so if it is off the fuel trims will be off and your fueling is off

[jimmyblue]

If you are in closed loop you must be commanding
14.7:1 AFR. People use the trims to determine the
correction needed, to true up commanded/actual.
However, -what- needs trued, depends on what you
did and where the engine is in the operating envelope
(MAF? VE table? Or just change the fuel filter?).