Mattjin

I have had these two maps bugging me for the last few months and today I finally found what they do. The first is the maximum trim that can be applied to the closed loop short term trim system. By default naturally it is in the positives. The second map is the min trim, of course in the negatives.

You will need this scale added to your list to view the trim correctly.

<scaling name="O2 Trim" units="%" toexpr="(x-128)/5" frexpr="(x*5)+128" format="%.1f" min="-25.6" max="25.4" inc="0.2" storagetype="uint8" endian="big"/>


And the maps...

80700010:

<table name="ST Fuel Max Trim" category="Fuel" address="3ae2" type="2D" level="2" scaling="O2 Trim">
<table name="Engine Temp" address="5c58" type="Y Axis" elements="8" scaling="Temp"/>
</table>

<table name="ST Fuel Min Trim" category="Fuel" address="3af0" type="2D" level="2" scaling="O2 Trim">
<table name="Engine Temp" address="5c58" type="Y Axis" elements="8" scaling="Temp"/>
</table>



88590015:

<table name="ST Fuel Max Trim" category="Fuel" address="30cc" type="2D" level="2" scaling="O2 Trim">
<table name="Engine Temp" address="70c2" type="Y Axis" elements="8" scaling="Temp"/>
</table>

<table name="ST Fuel Min Trim" category="Fuel" address="30da" type="2D" level="2" scaling="O2 Trim">
<table name="Engine Temp" address="70c2" type="Y Axis" elements="8" scaling="Temp"/>
</table>



94170015:

<table name="ST Fuel Max Trim" category="Fuel" address="369e" type="2D" level="2" scaling="O2 Trim">
<table name="Engine Temp" address="67a2" type="Y Axis" elements="8" scaling="Temp"/>
</table>

<table name="ST Fuel Min Trim" category="Fuel" address="36ac" type="2D" level="2" scaling="O2 Trim">
<table name="Engine Temp" address="67a2" type="Y Axis" elements="8" scaling="Temp"/>
</table>



98640014:

<table name="ST Fuel Max Trim" category="Fuel" address="389e" type="2D" level="2" scaling="O2 Trim">
<table name="Engine Temp" address="575c" type="Y Axis" elements="8" scaling="Temp"/>
</table>

<table name="ST Fuel Min Trim" category="Fuel" address="38ac" type="2D" level="2" scaling="O2 Trim">
<table name="Engine Temp" address="575c" type="Y Axis" elements="8" scaling="Temp"/>
</table>

jcsbanks

Nice job as always! If you have 88570008 handy that would be superb. I watch these trims live from my cell phone every day, would be nice to investigate more.

Mattjin

I was going to add this rom in the first place, but I thought I would let you beg a little

88570008:


<table name="ST Fuel Trim Max" category="Fuel" address="2dda" type="2D" level="2" scaling="O2 Trim">
<table name="Engine Temp" address="60bc" type="Y Axis" elements="8" scaling="Temp"/>
</table>

<table name="ST Fuel Trim Min" category="Fuel" address="2de8" type="2D" level="2" scaling="O2 Trim">
<table name="Engine Temp" address="60bc" type="Y Axis" elements="8" scaling="Temp"/>
</table>



What I found was that 128 (uint8) is the pivot point of 0% trim, which was pretty obvious with alot of other functions based on this number. Setting both maps to the same number locks the Short Term fuel trim to that fixed amount.

I did some experimentation with the Long Term trims, trying to track down what exactly decides which to use. I am tending to believe they are switched with either TPS or Airflow/Rev, but I have some more searching to do.

MR Turco

iTrader: (16)

So i understand the max table but i dont get the min table, is that min before it applies a long term trim? Also why would we want to alter this table?

Great stuff as always.

Mattjin

The min trim is in the negatives so it is technically the max amount of -ve trim, Max trim is in the positives. It is Short Term, and nothing to do with Long Term, it was just found while searching through any subroutines that use the LT Trim RAM addresses.

No idea why this would need adjusting, but the table is there in every rom and there are not that many more 2D tables to sort out. It is all part of tracking down the LT trims. It might be helpful to lower the amount if you have large injectors that fluctuate the ST trim alot at idle.

MR Turco

iTrader: (16)

oh i gotcha, it is pretty much just the compliment. Thanks for the response.

Mattjin

Nah, I was also a little surprised that a function like this would need different limits with engine temp. It has had me thinking what issues they ran into when setting up the evo's that required these limit changes. Some strange stuff in these roms I tell ya!

l2r99gst

iTrader: (2)

These may be useful when designing a flex fuel strategy. Increasing the range may allow an easier transition to proper fueling when filling up with E85 right after pump gas or vice versa, until the trmis stabilize and/or use the new injector scaling.

l2r99gst

iTrader: (2)

96530006:

Mattjin

The trouble is that they are already maxxed out by default at operating temperature.

l2r99gst

iTrader: (2)

Yep, just noticed that, so my comment is moot.

jcsbanks

I have noticed when it first goes closed loop that the initial trim is negative, presumably it is fighting the coolant enrichment.

Appauldd

iTrader: (22)

Now if only someone can find the LTFTs the crossover points would help so much in tuning Hz at idle with hard pipes and cams when you have to raise idle to 1k. At 1k RPM the Hz hovers at 40Hz and LTFT Low won't adjust. I bellieve by raising the crossover point we can fix the LTFT Low trim and idle stalling issue.

From what I have observed the STFT will bounce around as it peaks either + or - then the LTFTs will adjust. Once the ECU settles on an LTFT setting then the STFT will start to bounce around again. This process repeats over and over.

mplspilot

iTrader: (7)

Nice find.

nonschlont

iTrader: (3)

+1 Nice find.