On the Fast O2 R/L threshold vs MAP as well as the upper and lower zero error reference for slow O2 vs MAP tables...

I keep looking at the $8D stuff (ANHT, AUJP, AXCN, etc) and wondering why the values seem to have it getting leaner with higher MAP values (the O2 thresholds get smaller with higher MAP values). Seems very counter intuitive.

It shows up like this in both Tunerpro and Tunercat. I think back to the PE MAP enable threshold incident where Tunercat had it backwards in terms of MAP, but Tunerpro had it in terms of vacuum... and I wonder if the same thing is happening here except both Tunerpro and Tunercat...

So could it be that the kPa values are actually in terms of vacuum and not MAP? And that both TP and TC are mis-labeling the tables?

In the $DA3 code, the similar threshold tables are in terms of airflow, but the O2 values get larger with airflow (as one would expect).

 

Ok so I looked up the ANHT hac and found that it is still referring to the MAP as MAP and not vacuum... So to the first order, it appears that both TC and TP are correct in their table description and function...


*****************************************
* FUEL PID PARAMS
* MY 90 L98 Y & F CAR TYPE $8D CALIB.
*****************************************
;--------------------------------------------
; UPPER ZERO ERROR REF FOR SLOW o2 R/L vs MAP
;
;
;
; TBL = o2 VOLTS * 266
;--------------------------------------------
ORG L84A2 ; SLOW o2
; ERROR Kpa MAP
;----------------------------
L84A2: FCB 140 ; 0.619 20
FCB 148 ; 0.655 30


Going back to RBob's PM's when I had my PE drop out issue last summer, he was saying that the code actually uses vacuum and not MAP for the PE enable... and sure enough the code bears out what he says (not that was ever in any doubt!! )

**************************************************
* PWR ENRICH PARAMS
* ANHT TYPE $8D
**************************************************
L85FF: FCB 230 ; 8.1 Kpa VAC to ENABLE PWR ENR
; ARG = 256 - (Kpa * (256/80))


So it seems clear that there's a hard distinction on when they use MAP vs vacuum in the code...

But I guess that still doesn't answer the question about why they went leaner at higher map values... still doesn't make sense to me...

Any rate, what I'm finding is that the WB is showing around 15:1 during moderate (but non-PE) throttle... It doesn't seem like I'm losing power per se, as the car runs very well. I'm just curious why I can't get it to richen up in that "grey" area between regular part throttle operation and PE if I'm telling the ECM to bias the O2 readings to the high side. I have the swing points all the way up to .850 mV at the upper error reference table at high map values...

Maybe I need to put the damn WB O2 away so I can get back to ignorance is bliss mode...

 

Move all three tables up in value.

RBob.

 

Guess I'll keep going higher I suppose.

PM-ing with JP86SS, he brought up the possibility of putting in a positive offset in the r/l vs coolant table. Is that really possible?

again here though, on the r/l vs coolant table GM confuses me. In ANHT, and other 8D masks, they'e subtracting fuel at colder coolant temps... to the tune of 16 counts (or 70 mV if my math is correct). That again seems bass ackwards... especially since emissions seems to place high on priority for closed loop operation looking at other aspects of the tune...

I had zeroed out all my values in the coolant table, but it's be great if you could add positive offsets....

 

I used these in all entries of each table and it was noticeable on the NB sensor:

Lower: 585.9 mV
Upper: 620.62 mV
Mean r/l: 603.26 mV

It doesn't look like it can. That value is subtracted from the lower & upper slow O2 table values.

Likely already done but don't forget the AIR divert parameter.

RBob.

 

Thanks RBob... Hmmm ok I'll give those values a try. So you have no variation with MAP for your offset values...

Yes I already zeroed out the air divert offset value.

 

Same value across the whole table regardless of MAP. Car is old enough that a cat-con is illegal to install.

RBob.

 

Hmmm.... so it's cat converter that's driving the r/l threshold vs MAP profile?

I'm actually running high flow cats on my car just for keeping the exhaust smell under control...

 

Closed loop operation is required for reduced emissions, along with keeping the cat-con active and happy.

RBob.

 

The values

Lower: 585.9 mV
Upper: 620.62 mV
Mean r/l: 603.26 mV

... didn't really have much of an effect, good or bad over what I have no.

So in the spirit of "giving the engine what it wants" I went for broke and bumped the mean up to .950 at 100 kpa, tapering down to .600 at 20 kPa somewhat non-linearly, but very rich-biased at the high maps.

That finally woke things up. AFR's are now between 13.5 and 14.0 and the engine really likes it... I'll probably back down until I get the lean AFR again.

I was wrong earlier, I was in fact losing power... but just in that moderate-throttle, "in-between" area between non-PE and PE. Before, you could just kind of detect "by feel" when PE engaged since it would jump from 15-15.5:1 down to 12.5-12.75:1. Now the transition is very seamless.

Finally got this one licked...