ULTM8Z

One thing I don't understand is that on $8D (i.e, AUJP, ANHT, etc) is why for this table, the values get lower with higher map values. I would have expected that the O2 swing points trend richer with higher map values??

When I look at DA3 (the 93 LT1), they base the O2 swing points on airflow, but as expected, the higher the airflow, the higher the swing point value.

Am I missing something on 8D? The PE doesn't come in until 91 kPa map and upwards of 60-70% TPS, so you have to be into the throttle pretty heavily before you get the PE AFR's (and then you're essentially "open loop"). But at moderate throttle acceleration when still in closed loop, it seems like you'd want richer bias on the O2.

84Elky

Assumption is you are referring to the Table at 0x4b4: FAST o2 NOT Idling Rich/Lean Threshold .vs. MAP (Swing Point)

First must separate PE from not being in PE.
In PE
- Table not used. The INT is locked at 128 and there is no o2 adjustment of PW.

NOT in PE
Can't look at the table by itself and draw any real conclusions. Way too many variables and interactions. Just know that voltage is way rich and gets less rich and approaches 450mv Stoich as kPa increases. Regardless of the values we can assume GM set these values based on testing and likely also for EPA emissions compliance.

We also know that GM changed these values in other $8d 5.7L masks (see below).:

ULTM8Z

Thanks Elky. I do know that I re-did the table to be more inline with the DA3 tables and I do get a better throttle feel in that range between low throttle and WOT (when you haven't gotten into it far enough to engage PE).

What that seems to allows me to do is get richer-than-stoich AFR's outside of PE so I don't have to get full PE AFR at lower engine loads where it'd be too rich, so get a better seat-of-the-pants feel at moderate throttle. Also allows me to need less delta-MAP AE (I leaned out the AE map vs coolant by ~20%).

For example at moderate throttle before, the actual AFR was hovering around ~14.5 as the ECM was trying to maintain stoich. But now it gets down to around ~13.5. Then if I go further into the throttle and engage PE, I get down to my ~12.5.

So this allows me to delay the onset PE until the engine is really ready for it and give me a more linear feel to the throttle.

The upper and lower tolerance tables are 50mV above and below these nominals.

84Elky

Makes sense. Glad it's working that way. I have taken a different approach. Since I don't have cats, when I use CL I have the Swing Point set at 450v and upper and lower boundaries +/- 50mv. Then invoke PE at lower thresholds to get lower calculated AFR and thus more fuel.