fuel trims on e38 ?

[QuickSilver2002]

Fuel trims on this e38 are a bit confusing to me. Can someone explain what is going on?

Car is an 09 g8 gt.

Here is why I see in the editor (stock tune).
LTFT boundries
RPM
low - 3968
mid - 8192
high - 8192

MAP
low - 124
mid - 256
high - 256


then when I scan I see the following FTCs only
0,1,7,8,9,14,15

The stange part is there is no specific pattern to the map values in these logged cells. Most of the WOT stuff seems to go to cell 9, but there is also some part throttle there but I can't seem to identify the matrix.

[Chris@HPTuners]

looks like a bug, the code switched to airflow based boundaries in 08 i believe i don't think MAP is used anymore. I need to look into this.

Chris...

[QuickSilver2002]

Thanks for taking a look.

FYI, I'm running
2.23.3548.19188 Beta

[Hito]

0 PurgOnAirMode5
1 PurgOnAirMode4
2 PurgOnAirMode3
3 PurgOnAirMode2
4 PurgOnAirMode1
5 PurgOnAirMode0
6 PurgOnIdle
7 PurgOnDecel

8 PurgOffAirMode5
9 PurgOffAirMode4
10 PurgOffAirMode3
11 PurgOffAirMode2
12 PurgOffAirMode1
13 PurgOffAirMode0
14 PurgOffIdle
15 PurgOffDecel

[QuickSilver2002]

Good info above, but what is the definition for airflow mode 1-5.

From what I can tell so far, Cell 1 is all normal driving at light throttle. Then cell 9 is PE (guessing this is becase evap purge stops).

Where do LTFT for 9 come from, since stft stop.

Still confused, but there seems to be more clues now.

[Chris@HPTuners]

yes there are only 15 cells now

cell 0-5 Airflow based, Purge On
cell 6 Idle, Purge On
cell 7 Decel, Purge On
cell 8-13 Airflow based, Purge Off
cell 14 Idle, Purge Off
cell 15 Decel, Purge Off

We're adding the airflow mode boundaries, the MAP & RPM tables are incorrectly referencing the airflow mode boundary tables for newer E38 and probably E67 OS.

In your case the airflow mode cell boundaries are:

Purge Off
31, 64, 64, 64, 64

Purge On
31, 64, 64, 64, 64

This means that for EVAP Purge Off when the Airflow Mode is less than 31 you are Cell 0, between 31-64, cell 1 and above 64 (which can't actually happen cell 2 (they haven't used all 6 cells). Same for Purge On but cells 8,9,10.

The Airflow Mode is determined from the Airflow Mode vs Airflow table.

[QuickSilver2002]

Thanks a bunch Chris, this is making more sense now.

So the main operating cells (in my case) are 0,1 for purge on and 8,9 for purge off.

Here is the part that confuses me (from what I'm seeing). The car runs in 0 or 1 most of the time and then goes to cell 9 whenever in PE (I guess the purge goes off under PE). But it also runs in 9 when the car is frist started when it is cool out and there is enough airflow (guess the purge is off then).

So it almost seems that it is learning fuel trims for WOT when the motor is cold. It seems really odd that they would set it up that way from the factory. What am I missing.

[Chris@HPTuners]

yeah EVAP purge requires vacuum to draw the vapor into the manifold. That's why it disables at high throttle. Purge only enables once the engine warms up a little so you get tighter emissions control during cold startup. I don't know why they don't use all six available cells, seems a waste...

when we fixup the tables for this you will be able to adjust it. You can mess with it now but keep in mind only the first 3 of the 5 boundaries are shown. Divide the RPM table values by 128 to convert to Airflow Mode. For the MAP values divide by 4. Or just wait until we fix it properly.

Keep in mind that if you change the Airflow Mode vs. Airflow table it will also effect a lot of closed loop parameters (gains, delays etc.) so probably wouldn't mess with that one.

[carlrx7]

Keep in mind that if you change the Airflow Mode vs. Airflow table it will also effect a lot of closed loop parameters (gains, delays etc.) so probably wouldn't mess with that one.

how do we handle this table when scaling? specifically, the closed loop vs airflow table on the e38

[Chris@HPTuners]

how do we handle this table when scaling? specifically, the closed loop vs airflow table on the e38

when scaling what exactly?

[QuickSilver2002]

A few more related questions.

Is there anything to control evap purge right now for the e38. I remember there being ECT treshhold and a few other vacuum parameters for the older PCMs, but I can't find anything on the e38.

If there are not current calibration parameters, can you just explain the strategy/sensors it uses.


Does e38 still do the WOT LTFT thing where the trims are only applied in PE when positive for that cell.

[Chris@HPTuners]

A few more related questions.

Is there anything to control evap purge right now for the e38. I remember there being ECT treshhold and a few other vacuum parameters for the older PCMs, but I can't find anything on the e38.

If there are not current calibration parameters, can you just explain the strategy/sensors it uses.


Does e38 still do the WOT LTFT thing where the trims are only applied in PE when positive for that cell.

i don't know about EVAP stuff, its probably complicated.

I'm sure the fuelling still disregards negative LTFT's, although i don't think they go to zero on the scanner anymore.

[carlrx7]

when scaling what exactly?

Sorry, bringing it back from the dead,

Scaling the IFR to fit injectors greater than 63.5

I installed ID1000's so i scaled my tune down by 50% to make them fit.

scaled the mode table by just moving the columns. is there anyway to change the axis's instead so i dont lose any modes?

-Carl

[wstaab]

"The Airflow Mode is determined from the Airflow Mode vs Airflow table."

Where is this table located in the E38 and E67 ECU tables in HPTuners?

[carlrx7]

Engine : Fuel : Open & Closed Loop : General : Mode vs. Airflow