I want to save gas - Lean Cruise

[BJM]

I want to try a lean cruise patch for myself in my own chip. Before anyone asks I do not want to buy a chip to do this. I have written most of this but am having trouble figuring out how to set the A/F properly.

Assumptions
1. I will only allow lean cruise when highway spark mode is active (4th gear, TCC locked, LV8<128)
2. I will further constrain it so it won't be active with LV8<40-50 or so, (TBD)
3. I use the highway A/F ratio at $324B and set it to $66 = 16.1:1 as a start for 40<LV8<70.
4. I will add a bit of fuel for 70<LV8<100. ~15.5:1
5. I will add still more for 100<LV8<128. ~15.0:1
6. To prevent screwing up my BLMs I will turn off C/L when using lean mixtures. Kind of like the O/L code built into the car already.

I wrote a patch that intercepted what I thought was the final A/F calculation at $3C3D and jumped to my patch. I did all of the above and jumped back again. For 16:1 I wrote the value $0066 (102 decimal) into location $91,$92 which is what I thought I had to do.

It mostly worked, DS showed highway spark mode enabling and then a couple of frames later it went into O/L but the A/F ratio according to DS was 0.1:1! Obviously screwy, on top of that the injector PW went to 173%!!!, the O2 did not show it going rich but I only let it do it for a second or 2. I let off on the gas and the normal fueling picked up again. If I stepped on the gas it would kick out of highway mode just fine and worked normally. I am somehow modifying the A/F ratio incorrectly.

Have I picked the wrong location to set the A/F ratio? Is my value getting modified further in the code somewhere? I assumed that no matter what A/F ratio was calculated, mine would overwrite it.

 

[BoostKillsStres]

Highway A/F mode is never used in the chip if you search for 342B, you'll see its never referenced.

 

[BJM]

I put a value there and use it in my patch. I put 16:1 there.

 

[Eric Stage I]

Sounds like $91,92 doesn't have the right value (0066) in it.

What method did you use to get the value from 324B and save it into 91,92?


Eric

 

[BJM]

Basically after making sure I was within the constraints listed above I load the value of #$66 into Acc B from $342B, I add a little depending on load (either another #$04 or #$08). I then clear Acc A (I was testing conditions with it). Finally, I save Acc D to $91, which should be $91,$92.

F6 34 2B LDAB $342B
4F CLRA
DD 91 STAD $91

Does that sound right? I think D should be #$0066 or a little bigger and is saved onto $91 and $92.

 

[Eric Stage I]

That looks fine.

Are you jumping out at 3C3D or somewhere else?


Eric

 

[BJM]

I actually let the normal STD $91 at $3C3D occur and jump out after where the check for external equipment occurs. I'll just post everything here.

This is where I make the JMP out.

3C3D: DD 91 STD $91 Need to store original A/F value as calculated before doing Lean cruise checks. FuelTrim = D
3C3F: 7E 3D 97 JMP $3D97 JMP to Lean Patch
3C42: 01 NOP
3C43: 01 NOP
3C44: 97 00 STAA $00 Store flags again unaltered.
3C46: 96 0B LDAA $0B
3C48: 84 FB ANDA #$FB ; Enable Block Learn /0B04
3C4A: 97 0B STAA $0B

Here is the actual patch I JMP to.

3D97: 96 04 LDAA $04 Highway Mode Flags
3D99: 84 F7 ANDA #$F7 Zero Bit 3 - new Highway Mode O/L bit.
3D9B: 85 10 BITA #$10 Check Bit 4
3D9D: 27 24 BEQ $3DC3 If no highway mode, branch

Here if highway mode active.

3D9F: DE EA LDX $EA $00EA - Timer: Time since run enable (unsigned word max. 65535 [18hrs 12 minutes])
3DA1: 8C 00 1E CMPX #$001E Compare to 30 seconds?
3DA4: 23 1D BLS $3DC3 If run time <= limit (seconds), branch

Need to check if LV8 too low.

3DA6: D6 23 LDAB $23 $0023 - Filtered Load Variable (LV8)
3DA8: C1 32 CMPB #$32 Compare to low LV8 limit.
3DAA: 23 17 BLS $3DC3 If LV8<50, branch to end
3DAC: 17 TBA Move LV8 from B to A. Need to make comparisons using A with A/F in B below. Overwrites flags in A.
3DAD: F6 34 2B LDAB $342B Here if able to load Lean A/F, this is basic ratio for low loads. LV8 from 40-70.
3DB0: 81 46 CMPA #$46 Is load above 70?
3DB2: 25 09 BCS $3DBD If LV8<70, branch.
3DB4: CB 04 ADDB #$04 Here if LV8>70, add fuel. LV8 from 70-100.
3DB6: 81 64 CMPA #$64 Is load above 100?
3DB8: 25 03 BCS $3DBD If LV8<100, branch.
3DBA: CB 04 ADDB #$04 Here if LV8>100, add fuel. LV8 from 100-128.
3DBC: 4F CLRA Need to have A clear as part of D.
3DBD: DD 91 STAD $91 Store A/F in $91-92. A is clear, B is A/F set according to LV8.
3DBF: 96 04 LDAA $04 Need to reload flags.
3DC1: 8A 08 ORA #$08 Set Lean Cruise flag to trigger O/L.
3DC3: 97 04 STAA $04 If no lean cruise, from branches the flags were kept in A with checks made in B and flag for O/L is lowered. If lean cruise is on, Bit 3 is high.

3DC5: 96 00 LDAA $00 Load flags again.
3DC7: 7E 3C 42 JMP $3C42 Return to code.


You will notice I set a new flag to indicate we should be in O/L. I redirect that JMP at $37A3 that lets you into the C/L routine to turn off C/L if that bit is set. That extra little routine goes below the one above. That part seems to work fine, its going in and out of C/L when it should. I am sure this could be smaller but first I just want to get it working. I don't really know why I bother checking for run time but on cold mornings I didn't want it to operate for at least 10 minutes, its only set to 30 seconds right now.

 

[Eric Stage I]

3DB2: 25 09 BCS $3DBD If LV8<70, branch.
3DB4: CB 04 ADDB #$04 Here if LV8>70, add fuel. LV8 from 70-100.
3DB6: 81 64 CMPA #$64 Is load above 100?
3DB8: 25 03 BCS $3DBD If LV8<100, branch.
3DBA: CB 04 ADDB #$04 Here if LV8>100, add fuel. LV8 from 100-128.
3DBC: 4F CLRA Need to have A clear as part of D.
3DBD: DD 91 STAD $91 Store A/F in $91-92. A is clear, B is A/F set according to LV8.

On those 2 branches in red, the CLRA is being bypassed, allowing LV8 to remain in A, screwing up the $91 trim.

 

[BJM]

Wow Good eyes, I will go try to fix that right now.

 

[BJM]

That fixed it perfectly. I shortened the 2 branches by one each and it works great. I just got back from a run and the car never felt too lean anywhere. My leanest setting is now 16.1:1. How lean do these cars operate? I don't want to go nuts or anything.

Thanks for all the help.

Gotta love the internet, I am typing this while still in my car hooked up to DS outside my house and am hooked up to my wireless link.