O2 Swing Points

[EagleMark]

As I understand it ".450 V = 14.7 AFR" is gasoline only (E00) stoich, and .450 V = 14.2 AFR would be a E10 stoich. It's the design of automotive O2's that make .450 = stoich. Previous to ethanol fuels I guess all automotive tuning people just picked up on calling 14.7 = stoich and it has stuck. A car running E10 will still manage the rich/lean based on the .450 O2 reading. Now that leads into your second question.. I only have OBD1 but, it's similiar to OBD1 below are pics of stock and performance tune fueling tables "Closed Loop Mode Vs Airflow" and "Fast O2 rich/Lean Vs CL Mode" you can see the stoich switches on the lean side at idle and goes richer at low AFGS flows then goes to 451 after 64 AFGS, My performance tune (with HotCam and 1.6 RR's) is leaned out throughout all the ranges. I have also noticed GM uses different voltage values in the stock tunes for the manual (M6) cars Vs the A4's. I assume lots of trial and error to get the stock settings.

Here is stock..



And here is a performance tune.

That kinda proves my point that .450 is Stoich and has nothing to do with AFR! Dam internet rumors again...

The CL Vs Airflow (also differant names in differant masks) is becuase Narrowband o2 sensors have different voltages for stoich depending on how much airflow there is, this table compensates for it.

As 1project2many describes tighening up the swing points keeps closer to Stoich. Seems the newer and newer calibrations do not even use differant values there. High and low are the same. When I set mine to .450 on both sides my data is much cleaner.

Here's a graph of why I'm leary of changing higher or in your case lower to acheive a differant AFR. Just so inaccurate outside center of what some charts show as 450 and some 500.