Lean Cruse Patch

[BradB]

Lean Cruise Patch

Lean cruise: I want to add this feature to my chips
for my own use so I've been reading the code and toying
with a few ideas. First there is already an
excellent highway cruise indicator function to test for so
determining that mode is done (highway cruise spark mode).

Now comes the hard part, how to change the AF ratio and
stay in closed loop.
From looking at the code 2 ways come to mind, first change
the O2 sensor switch points although given the characteristics
of the stock sensor I'm not sure you can reliably go too far
from 14.7. The code that gets them is 3 bytes and it's in prom
so change it to a jump to a test and substitute subroutine could
be created. This would then change them to a lower value for a
lean cruise.

The Closed loop AF Ratio constant could be done the same
way but 2 of the 4 calls to it are in rom and I think they are the
important ones.

No I do not want to buy XX's chip to acomplish this

So what do you think?

 

[BM Computer Src]

Actually,

We did play with adjusting the A/F ratio for highway spark mode, but noticed no changes in mileage. After discussing it with a few users and Mr. Testa, he provided the information to advance the spark about 3-4 degrees in the cruise load and rpm's. This has come to work well for a lean cruise. The load numbers to adjust are 32-128 (probably overkill, but it wont hurt) and RPM's from 400-3600, again you probably wont be "crusing" at 3600, but you get the point.

Good luck, and enjoy.

-Bob

 

[bruce]

Originally posted by BM Computer Src
Actually,
We did play with adjusting the A/F ratio for highway spark mode, but noticed no changes in mileage. After discussing it with a few users and Mr. Testa, he provided the information to advance the spark about 3-4 degrees in the cruise load and rpm's. This has come to work well for a lean cruise. The load numbers to adjust are 32-128 (probably overkill, but it wont hurt) and RPM's from 400-3600, again you probably wont be "crusing" at 3600, but you get the point.
Good luck, and enjoy.
-Bob

You have to actually read the code to see what is in use. There are several AFR settings, but in oem form only 2 of the 4 are used.

 

[bruce]

Originally posted by BM Computer Src
Actually,
We did play with adjusting the A/F ratio for highway spark mode, but noticed no changes in mileage. After discussing it with a few users and Mr. Testa, he provided the information to advance the spark about 3-4 degrees in the cruise load and rpm's. This has come to work well for a lean cruise. The load numbers to adjust are 32-128 (probably overkill, but it wont hurt) and RPM's from 400-3600, again you probably wont be "crusing" at 3600, but you get the point.
Good luck, and enjoy.
-Bob

Hit reply too fast,
anyway,
with an Extender chip, when using a WB, you can see the moment it goes from 14.7 to lean cruise.

 

[BradB]

Right, I played and searched the code to see
if 0x342B Highway mode A/F Ratio would work
but it is never accessed. 0x342A is but accessed
from both rom(2) and eprom(2) so inserting a jump to
a patch won't work. Thats why I was looking at
the O2 sensor Voltage switch points, all 4 locations
(0x341B-0x341E) are accessed only from eprom. That
way I could change the cmpa (compare) to a jsr and
test for highway mode, 0x0004 bit4 (flag), and if true
sub the lean O2 switch points then return, and the
code should be happy. maybe?

 

[terryk]

If anyone can help here I'd appreciate it. I need the patch to enable the lean cruise.

 

[BradB]

I've been reading and playing. Opinions anyone?


Old code
3E4D: B1 34 1E CMPA $341E if (A > O2 R-L HIGH THRESH SLOW TRIM) [#$90]
3E50: 22 08 BHI $3E5A goto $3E5A
3E52: B1 34 1D CMPA $341D if (A >= O2 R-L LOW THRESH SLOW TRIM) [#$70]
3E55: 24 0A BCC $3E61 goto $3E61

Jump to the Lean Cruise Patch
3E4D: 7E 3B 1C JMP $3B1C Goto $3B1C Lean cruise patch Decision code

Test for Cruise mode
3B1C: 96 04 LDAA $04 get $0004 - Flags Bit-4 = Highway mode spark advance
enabled
3B1E: 85 04 BITA #$10 Check if cruise is on
3B20: 27 06 BEQ $3B28 goto LEAN cruise O2 code otherwise do normal
3B22: B1 34 1E CMPA $341E if (A > O2 R-L HIGH THRESH SLOW TRIM) NORMAL
3B25: 7E 3E 50 JMP $3E50 Goto $3E50 Return to normal code

Jump to the Lean Cruise Patch
3B28: 7E 38 DA JMP $38DA Goto $38DA Lean

Lean Cruise Patch
38DA: B1 37 98 CMPA $3798 if (A > O2 R-L HIGH THRESH SLOW TRIM) LEAN
38DD: 22 08 BHI $38E7 goto $38E7
38DF: B1 37 99 CMPA $3799 if (A >= O2 R-L LOW THRESH SLOW TRIM) LEAN
38E2: 24 06 BCC $38EA goto $38EA
38E4: 7E 3E 57 JMP $3E57 Goto $3E57 Return to normal code
38E7: 7E 3E 5A JMP $3E5A Goto $3E5A
38EA: 7E 3E 61 JMP $3E61 Goto $3E61

Location 3798 and 3799 would be your new lower O2 voltages

 

[chris]

Brad
Any results from you patch?

 

[TurboDave]

Originally posted by bruce
Hit reply too fast,
anyway,
with an Extender chip, when using a WB, you can see the moment it goes from 14.7 to lean cruise.

Not only that, when I have lean cruise turned on in my extender, I can see it working on the EGT ! That surprised me a little, but makes perfect sense now. The Extender's lean cruise actually works.

 

[TurboDave]

As for getting a lean cruise patch to work. Wish you luck, but you'll be left to your own expertise on this one.

I doubt one of the very very few (only 1 person that I know of) that have the function actually working their chips are going to give out the code secrets.

 

[bruce]

I'm given up on the cruise.
While it's a neat idea, GNs aren't meant to compete with a 1600 econobox, for MPG.

I've run a lean cruise chip, and broken 30 MPG a couple times.

I've also tried a LOW TIMING CHIP meaning in cruise I just use 20 somthing degrees of timing. And run slightly rich.

On a 400 mile drive now, my oil pressure is the same after 400 as after 20 miles. Running less timing has a drastic effect on oil temps.. Piston domes stay cooler, and now I can cruise at any speed on want in any temp.. I'd also venture a guess the bearings will stay happier longer......

 

[dennisL]

Originally posted by BM Computer Src
... advance the spark about 3-4 degrees in the cruise load and rpm's. This has come to work well for a lean cruise. The load numbers to adjust are 32-128 (probably overkill, but it wont hurt) and RPM's from 400-3600, ....

I'm a little confused ... is this advance to be added to the main table? Because 4 degrees (mostly) is already added when the TCC is locked in 4th gear and LV8 is 48 - 127 by table $31F4. Any comments?

Just to add .02, I played a little with an attempt to achieve highway lean cruise but I did it by using the Highway AFR. All it ended up doing was wacking the BLM's so bad that normal driving was messed up (after a highway ride) until it re-learned the cells. I took it out. I guess my point is, don't forget that you only have one set of BLMs. If these change during lean cruise (because its working) then you're around town driving is adversely affected.

 

[ijames]

All it ended up doing was wacking the BLM's so bad that normal driving was messed up (after a highway ride) until it re-learned the cells. I took it out. I guess my point is, don't forget that you only have one set of BLMs. If these change during lean cruise (because its working) then you're around town driving is adversely affected.

I don't think it would make sense to leave learn mode enabled during a lean cruise, for just that reason.

 

[Eric Stage I]

Doesn't learn mode shut off anyway if closed loop a/f doesn't match whats in 342A because of this:

F03E D6 92 LDAB $92 Load current closed loop a/f
F040 F1 34 2A CMPB $342A compare to $342A (programmed closed loop a/f)
F043 26 0D BNE $F052 if closed loop a/f does not equal $342A goto $F052 (Turn off Learn)

Seems like half the programming for lean cruise is already there.

 

[ijames]

Yes, but depending on where you insert your patch it might do once cycle of blm learn before it notices that the far has changed so you might want to turn off learn yourself. Just a thought.

 

[chris]

Any body have any luck with this lean cruise or any other patch?

 

[Low Budget]

More discussion's like this are needed.

This is the type of conversation (yes, inserting my opinion here) I think should be going on in the

chip section. Not just "who's chip should I buy". I don't think I'm wrong in saying the vast majority

of us aren't in this "Buick Thing" for the money, but for our own enjoyment. Let's help advance the

technology as much as we can, and worry less about giving away secrets! This thread is my idea of

a good read. I must really work my brain to comprehend it, but I AM LEARNING. My thanks to all

who have contributed to this thread! I appreciate the help!