mrfred

iTrader: (50)

September 7, 2011 - I've determined the variables that act as trims to the ISCV Demand. They are explained below.

August 10, 2011 - I found the power steering adder for the ISCV Demand calculation. Turns out that they are two of the existing tables; one is a function of baro and the other is a function of intake air temp. I have updated the names of the tables to reflect their usage for power steering pressure compensation.

October 21, 2010 - Updated list of tables to include tables that have a strong effect on throttle hang. These additional tables were original deemed to be "decel fuel cut delay" tables. They are actually ISCV demand tables. The new tables are the four listed just before the Idle Stepper lookup table at the very end.

Notes on ISCV disassembly

**How the Idle Stepper System Works**
The idle stepper lookup table has two axes. One is coolant temp, and the other axis was unknown. Some people have been interpreting this unknown axis as RPM or load. Turns out its not an engine operating parameter, but instead its a unitless parameter that is the sum of contributions based on the status of several different engine parameters including RPM, TPS, coolant temp, intake air temp, AC compressor status, whether the starter is cranking, and more. Each of these engine parameters has a contribution to the total value. For instance, when the AC compressor switches on, this parameter increases by a set amount to attempt to compensate for the additional load placed on the engine when the AC compressor is running.

For this writeup, I'll call this unitless value "ISCV Demand". There are tables that control the effect of the more common engine operating parameters (RPM, TPS, coolant temp) on ISCV Demand. Unfortunately, there are many more tables based on some particular engine parameters (e.g. coolant temp) than I imagined when I got started on this disassembly effort with no easy way to explain when one table is used instead of another. This makes it difficult to know which table to adjust for tuning ISCV. For instance, there are six different ISCV Demand vs Coolant Temp tables. The reason that there are so many different tables is that ISCV Demand gets calculated differently based on what the engine is doing, so there are some tables that are unique to what the engine is doing, e.g., starter cranking, or decel. I've put quite a bit of time into trying to determine what factors uniquely determine which of these tables will be used, but to be honest, the number of factors that play a role are greater than the time I have to try to figure out. The best thing I can do at this point is to post the tables and let people tinker if they have interest. The tables for the 88590015 ROM are shown below. I've indicated tables that work as pairs or sets with "*" values. There are some notations indicating the subroutines where these tables are used in the 88590015 ROM. Those can be ignored. I've also included the Idle Stepper Position Lookup table with the "ISCV Demand" units. As usual, I don't have the time to try to find these tables for other ROMs, at least for now.

ISCV Demand trims: Even with huge number of parameters that control the ISCV Demand value (e.g. baro, IAT, RPM), the ISCV Demand value needed to reach the target idle may not be perfect and usually isn't. So their are ISCV Demand trims that make up the difference. MUT_08 is the trim when the AC compressor is off, and MUT_0A is the trim when the AC compressor is on. The EvoScan formula for the ISCV Demand trims is Eval="100*(x-144)/255".

There are five subroutines where the idle stepper value is calculated. The conditions that set when each subroutine is called are:

Sub_A) Ignition "on", but engine "off"

Sub_B) Starter is cranking

Sub_C) Engine running, during decel

Sub_D) Engine running, not decel

Sub_E) Not yet known

Sub_B = Sub_A + a routine to trim the stepper to hit the target idle

Sub_D = Sub_C + a routine to trim the stepper to hit the target idle

Set E runs in place of the other four subroutines. Don't know yet when its called. There are a ton of flags involved with ISCV control, and I'm not going to kill myself chasing them all down.

Side Note: One thing that is a bit puzzling about the ISCV control system is that the ISCV stepper position lookup table picks the stepper position based on ISCV Demand and Coolant Temp axes. That fact that there is a coolant temp axis is unexpected because the effect of coolant temp is already folded into the ISCV Demand value. I think perhaps that Mitsu did not have coolant temp folded into the ISCV Demand in the early days, but then added it later and kept the 3D table as a legacy item.

With that, here are the tables for the 88590015 ROM:

-----
<scaling name="ISCV_AX2_8" units="% Demand" toexpr="x*100/255" frexpr="x*255/100" format="%.1f" min="0" max="200" inc="0.5" storagetype="uint8" endian="big"/>
<scaling name="ISCV_AX2_16" units="% Demand" toexpr="x*100/255" frexpr="x*255/100" format="%.1f" min="0" max="200" inc="0.5" storagetype="uint16" endian="big"/>

<table name="ISCV Demand Target Idle Trim (sub_1ECF6)" category="ISCV Control" type="2D" address="3dec" level="2" scaling="ISCV_AX2_8">
<table name="Target Idle Deviation" type="Y Axis" address="6c9e" elements="9" scaling="RPMTarget"/>
</table>

<table name="Target Idle ISCV Trim Adjust Frequency" category="ISCV Control" address="14c2" type="1D" level="2" scaling="Time"/>

<table name="ISCV Demand Below 500 RPM Idle Recovery Adder (sub_1E2C8)" category="ISCV Control" address="1516" type="1D" level="2" scaling="ISCV_AX2_16"/>


<table name="ISCV Demand Startup CTS Adder (sub_1EBB8)" category="ISCV Control" type="2D" address="3d60" level="2" scaling="ISCV_AX2_8">
<table name="Coolant Temp" type="Y Axis" address="6fde" elements="8" scaling="Temp"/>
</table>


<table name="ISCV Demand General CTS Subtractor (sub_1EBE6)" category="ISCV Control" type="2D" address="3e0a" level="2" scaling="ISCV_AX2_8">
<table name="Coolant Temp" type="Y Axis" address="6fde" elements="8" scaling="Temp"/>
</table>


<table name="ISCV Demand Baro Adder (FFFF6E98) (sub_1E1EE)" category="ISCV Control" type="2D" address="3dda" level="2" scaling="ISCV_AX2_8">
<table name="Baro" type="Y Axis" address="6e28" elements="5" scaling="Baro16"/>
</table>

<table name="ISCV Demand RPM Adder* (sub_1EFC0)" category="ISCV Control" type="2D" address="41d8" level="2" scaling="ISCV_AX2_8">
<table name="RPM" type="Y Axis" address="6b7a" elements="10" scaling="RPM"/>
</table>

<table name="ISCV Demand TPS Subtractor* (sub_1EFC0)" category="ISCV Control" type="2D" address="6810" level="2" scaling="ISCV_AX2_8">
<table name="Shifted TPS" type="Y Axis" address="810c" elements="11" scaling="ThrottlePercentage"/>
</table>

<table name="ISCV Demand RPM Adder [rpm > 4500, load > 170, speed > 12 mph] (sub_1EFC0)" category="ISCV Control" type="2D" address="65de" level="2" scaling="ISCV_AX2_8">
<table name="RPM" type="Y Axis" address="7fb0" elements="10" scaling="RPM"/>
</table>

<table name="ISCV Demand CTS Adder #1** (sub_1F1F8, sub_1EA0C, sub_1F596) [sub_1EFC0]" category="ISCV Control" type="2D" address="3d38" level="2" scaling="ISCV_AX2_8">
<table name="Coolant Temp" type="Y Axis" address="70c2" elements="8" scaling="Temp"/>
</table>

<table name="ISCV Demand CTS Adder #2** (Post WOT) (sub_1F1F8) [sub_1EFC0]" category="ISCV Control" type="2D" address="54e6" level="2" scaling="ISCV_AX2_8">
<table name="Coolant Temp" type="Y Axis" address="7070" elements="8" scaling="Temp"/>
</table>

<table name="ISCV Demand CTS Adder #1a*** (sub_1F2C6, 1F596) [sub_1EFC0]" category="ISCV Control" type="2D" address="51b0" level="2" scaling="ISCV_AX2_8">
<table name="Coolant Temp" type="Y Axis" address="70c2" elements="8" scaling="Temp"/>
</table>

<table name="ISCV Demand CTS Adder #1b*** (sub_1F2C6) [sub_1EFC0]" category="ISCV Control" type="2D" address="3d4c" level="2" scaling="ISCV_AX2_8">
<table name="Coolant Temp" type="Y Axis" address="70c2" elements="8" scaling="Temp"/>
</table>

<table name="ISCV Demand CTS Adder #2*** (Post WOT) (sub_1F2C6) [sub_1EFC0]" category="ISCV Control" type="2D" address="5502" level="2" scaling="ISCV_AX2_8">
<table name="Coolant Temp" type="Y Axis" address="7070" elements="8" scaling="Temp"/>
</table>

<table name="ISCV Demand RPM Adder (Moderated by Baro, IATS) (FFFF6EA8) (sub_204B6) [sub_1EFC0]" category="ISCV Control" type="2D" address="672a" level="2" scaling="ISCV_AX2_8">
<table name="RPM" type="Y Axis" address="802a" elements="10" scaling="RPM"/>
</table>

<table name="ISCV Demand Power Steering Baro Adder**** (FFFF7C0E) (sub_1F6E6) [sub_1EFC0]" category="ISCV Control" type="2D" address="6adc" level="2" scaling="ISCV_AX2_8">
<table name="Baro" type="Y Axis" address="6e28" elements="5" scaling="Baro16"/>
</table>

<table name="ISCV Demand Power Steering IATS Adder**** (FFFF7C0E) (sub_1F6E6) [sub_1EFC0]" category="ISCV Control" type="2D" address="6ae8" level="2" scaling="ISCV_AX2_8">
<table name="Intake Air Temp" type="Y Axis" address="714a" elements="8" scaling="Temp"/>
</table>


<table name="ISCV Demand TPS Adder, AC off (FFFF6E84) (mattjin fuel cut delay)" category="Idle" address="3d6e" type="2D" level="1" scaling="ISCV_AX2_8">
<table name="TPS" address="6f9a" type="Y Axis" elements="7" scaling="ThrottlePercentage"/>
</table>

<table name="ISCV Demand TPS Adder, AC on (FFFF6E84) (mattjin fuel cut delay)" category="Idle" address="3d82" type="2D" level="1" scaling="ISCV_AX2_8">
<table name="TPS" address="6f9a" type="Y Axis" elements="7" scaling="ThrottlePercentage"/>
</table>

<table name="ISCV Demand CTS Addder (FFFF6E84)" category="Idle" address="4e56" type="2D" level="1" scaling="ISCV_AX2_8">
<table name="Coolant Temp" address="6fde" type="Y Axis" elements="8" scaling="Temp"/>
</table>

<scaling name="ScaleBase64Adder" units="Mult. Factor" toexpr="(x+64)/64" frexpr="64*(x-1)" format="%.2f" min="0" max="10" inc="0.05" storagetype="uint8" endian="big"/>
<table name="Baro Mult. Factor for ISCV Demand Adder FFFF6E84" category="Idle" address="6b68" type="2D" level="1" scaling="ScaleBase64Adder">
<table name="Baro" address="6e4e" type="Y Axis" elements="5" scaling="Baro16"/>
</table>


<table name="Idle Stepper Lookup Table" category="ISCV Control" type="3D" address="3e31" scaling="ISCVSteps">
<table name="Coolant Temp" type="X Axis" elements="8" address="7164" scaling="Temp"/>
<table name="ISCV Demand" type="Y Axis" elements="27" address="717e" scaling="ISCV_AX2_16"/>
</table>
-----

MR Turco

iTrader: (16)

oh mai....

So part of this effort i'm sure was to combat the throttle hang issue. I would assume if we could determine the demand when throttle hang is experienced we could try to figure out which table is controlling the problem?

house_of_senate

iTrader: (1)

So we should be able to use these to get rid of throttle hang no? Also, for my newbness, can I just copy these into the bottom of my rom xml under my tephra mod? Or do I need to replace the old ISCV stuff?

mrfred

iTrader: (50)

Yes, one of these tables more than likely controls the throttle hang. No prob to copy the tables to the bottom of your ROM xml under the tephra mod stuff. They will show up in a category called "ISCV Control". Ignore all the old ISCV stuff. For the most part its completely wrong.

house_of_senate

iTrader: (1)

Any idea of which tables to start on the throttle hang experimenting?

mrfred

iTrader: (50)

There are two tables where I have a (Post WOT) notation in the table name. Try those first. If those don't do it, then go next to the RPM-based ISCV Demand tables.

MR Turco

iTrader: (16)

mrfred, is there any way to log "% demand"?

mrfred

iTrader: (50)

Log MUT 76 in EvoScan. Use a scaling of 100*x/255.

MR Turco

iTrader: (16)

awesome thanks.

l2r99gst

iTrader: (2)

If you guys give me some time, I will find the tables in 96530006. Just don't know when I will get to it (today, tomorrow, over the weekend, etc).

Great work as always, mrfred!


Eric

sub7

+1 for 90550001

acamus

I believe I know that feeling ........

Nice writeup & good job ....

fostytou

iTrader: (15)

Evoscan equation for the newbs:

l2r99gst

iTrader: (2)

OK, from the best of my ability, here are the tables for 96530006.

****Notes****
Some of these were pretty tough to find, and since I'm not a disassembler, I'm not 100% on some of the tables. Explained below:

1. I couldn't find the 'ISCV Demand TPS Subtractor*' table. I kept in the code below, but commented out, with mrfred's address for 88950015. I found the place where it 'should' be, but there is nothing there.
2. I'm not certain on the 'ISCV Demand Baro Adder**** (FFFF7C0E) (sub_1F6E6) [sub_1EFC0]' table. I have included it below, but I think it's wrong. In96530006, the location I have has the values all as 100%, where in 88590015, they go from about 27% to 21%.
3. I'm not certain if the 'ISCV Demand IATS Adder**** (FFFF7C0E) (sub_1F6E6) [sub_1EFC0]' table. In 96530006, the values decrease from 47.1% to 31.4%, but in 88590015, they increase from 19.6% to 25.5%. It may still be right, but wanted to point it out.

I'm pretty sure all of the rest are good. But, I can't guarantee that, until someone skilled in disassebly takes a look. That being said, here you go:

Mattjin

Good work!

I tell you one adjustment that I have been searching for..... Power Steering ISCV Increase. You may have hit the nail on the head with the X-axis of the stepper lookup table too, because I can now see that the P/S input must shift this value up a little because I have found no other references to a 1D or 2D that cause the steps to increase.

A little info I noticed about the 3D table. It seems to be a min value table. Raising the values raises the minimum steps that ISCV will go to. Lowering the values does not necesarily lower the steps. Also most people have the axis backward. Y=8 X=27. It has the same Y axis header at the beginning of the table as do the other 3D tables.