AAC Valve Behavior

[Matt]

These are a low sale ECU so are low priority when it comes for looking for new maps. It all depends on time available

[my1path]

These are a low sale ECU so are low priority when it comes for looking for new maps. It all depends on time available

understood, if its on your to-do list (no matter how far down) I'll hope for the best.

Out of curiousity, what is your highest selling? I imagine its also your most developed as well?

[Matt]

We seem to do a lot of skylines (R32, R33 [R32 ECU], R34] and 180SX/200SX (SR20DET)

[Matt]

I've had a look through the AAC routine in this ECU today (traced back from the Consult AAC output register), I can see references to the Target Idle RPM lookup tables in the routine so this is definitely the correct code

However it's nothing like the HCR32 which at least had tables etc which we were able to figure out how to change pot position etc. The M30 code does some of its table lookups elsewhere and then references the resulting table value in other areas.

What I found:

Code: Select all

byte 0xFFBA ROM_FFBA_AAC
byte 0xFFA6 ROM_FFA6_AAC
word 0xFFA3 ROM_FFA3_AAC
byte 0xFFAD ROM_FFAD_AAC
word 0xF6A9 ROM_F6A9_AAC

These were referenced bytes in the routine but no idea what they do. You can try adjusting using the Display > Hex editor but results might be random!

[my1path]

I've had a look through the AAC routine in this ECU today (traced back from the Consult AAC output register), I can see references to the Target Idle RPM lookup tables in the routine so this is definitely the correct code

However it's nothing like the HCR32 which at least had tables etc which we were able to figure out how to change pot position etc. The M30 code does some of its table lookups elsewhere and then references the resulting table value in other areas.

What I found:

Code: Select all

byte 0xFFBA ROM_FFBA_AAC
byte 0xFFA6 ROM_FFA6_AAC
word 0xFFA3 ROM_FFA3_AAC
byte 0xFFAD ROM_FFAD_AAC
word 0xF6A9 ROM_F6A9_AAC

These were referenced bytes in the routine but no idea what they do. You can try adjusting using the Display > Hex editor but results might be random!

so I would paste those into the .adr?

I just plugged in an ECU off ebay (a18-60 k34)to test it. AAC behavior was different, the problem was less exaggerated and the AAC value did not go all the way up to 80 when driving. I downloaded it to my pc and I'm going to copy the needed items to it and see how it does. I attached the file for you to compare. I think it matches "F6670" 1991 bin already included but just in case. Maybe something is off in the file that does not show in software? (was using A18-A08 K30 "F6610" before as my starting points that's the ECU I have Nistune installed on)
This may effect my other thread on timing too...

[my1path]

I just plugged in an ECU off ebay (a18-60 k34)to test it. AAC behavior was different, the problem was less exaggerated and the AAC value did not go all the way up to 80 when driving. I downloaded it to my pc and I'm going to copy the needed items to it and see how it does.

Weather has been warmer so the high idle condition is probably not as exaggerated but I think this is helping. I'll know for sure when the next cold spell rolls through.
Looking at the consult view AAC behavior does seem a little different from the previous .bin I was using.

[Matt]

so I would paste those into the .adr?

no : You can try adjusting using the Display > Hex editor
Must be in expert mode to display the hex editor

Your ECU: m30 a18-60 k34.bin has part number F6670 (AT) 1991 so is a later version than F6610 (1990)

The addresses I listed is the same values in both of those ECUs

[my1path]

I'm not seeing where I make these changes am a reading it right?

[Matt]

There is a 0x8000 offset so entries in hex editor are:

Code: Select all

byte 0xFFBA => 7FBA
word 0xFFA3 => 7FA3, 7FA4
byte 0xFFAD => 7FAD
word 0xF6A9 => 76A9, 76AA

[my1path]

Ok here is what I have tried so far. The first value was default the second value is what I tried.

7FBA 06 > 00 no visible change
7FA3 01 > 00 no visible change
7FA4 68 > 00 n/c
7FAD 19 > 00 n/c
76A9 46 > 00 n/c
76AA 00 > 20 n/c

I saw no visible changes to AAC behavior but maybe I need to try other numbers (or characters?)
The Cold air this week really brings the idle up when the engine is warmed up. I turned down the idle screw until the AAC started to fluctuate 20-24. This helped. I may even turn it down enough to see AAC 30... This will certainly reduce how much it will raise idle coming to a stop but unfortunately it will also reduce how high it can lift my idle during warm up.

[Matt]

Unfortunately I don't have much else for this one. Code is just too different from the others to work out anything further. Disassembly can be difficult since it's all just a jigsaw puzzle with no instructions