7747 lean hiway cruise patch...a few q's...
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7747 lean hiway cruise patch...a few q's...
I want to try the 7747 lean hiway cruise patch. I'm not not 100% sure what a few of these commands do...
I'm not too clear on what LD026 thru LD02A does. Are these transition SA modifiers?
thanks
Code:
;--------------------------------------------- ; HIWAY SPARK ADDER QUAL'S ; QUALS FOR SPK ADDER TBL LD157 ;--------------------------------------------- LD024 FCB 96 ; 30 MPH, HWAY SPK ADV QUAL Thresh MPH, MIN ; VAL = MPH * 3.2 ; LD025 FCB 40 ; 40 Sec's HWAY SPK ADV QUAL MIN TIME Thresh (SEC/1) ; LD026 FCB 9 ; 2 SEC'S, SPK Time out reduce, (Sec * 5)-1)) LD027 FCB 40 ; 40 SEC'S, PWR ENR SPK TIME OUT ; LD028 FCB 112 ; 2800 RPM, MIN RPM FOR SPK SA DECAY ; LD029 FCB 39 ; Pwr Enr SPK Decay cool THRESH LD02A FCB 2 ; Pwr Enr SK ADV INCREASE, Deg, 1.4 Deg
thanks
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Re: 7747 lean hiway cruise patch...a few q's...
Originally posted by V8Astro Captain
I want to try the 7747 lean hiway cruise patch. I'm not not 100% sure what a few of these commands do...
I'm not too clear on what LD026 thru LD02A does. Are these transition SA modifiers?
thanks
I want to try the 7747 lean hiway cruise patch. I'm not not 100% sure what a few of these commands do...
Code:
;--------------------------------------------- ; HIWAY SPARK ADDER QUAL'S ; QUALS FOR SPK ADDER TBL LD157 ;--------------------------------------------- LD024 FCB 96 ; 30 MPH, HWAY SPK ADV QUAL Thresh MPH, MIN ; VAL = MPH * 3.2 ; LD025 FCB 40 ; 40 Sec's HWAY SPK ADV QUAL MIN TIME Thresh (SEC/1) ; LD026 FCB 9 ; 2 SEC'S, SPK Time out reduce, (Sec * 5)-1)) LD027 FCB 40 ; 40 SEC'S, PWR ENR SPK TIME OUT ; LD028 FCB 112 ; 2800 RPM, MIN RPM FOR SPK SA DECAY ; LD029 FCB 39 ; Pwr Enr SPK Decay cool THRESH LD02A FCB 2 ; Pwr Enr SK ADV INCREASE, Deg, 1.4 Deg
thanks
RBob.
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Originally Posted by escort_ford84
I dont see any type of leaning there, just spark advance
#5
So running high spark advance at high vacuum will lean the AFR right? Like 40-48 degrees in highway mode? i run about 35-38 wihtout any highway spark advance. my engine cruises on the hiway at 10" of vacuum in high gear.would 48 degrees be ok for highway mode?
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In some GM code they have separate lean modes and highway SA modes. Why, I don't know. Doesn't make sense that they would lean the mix without adding timing.
Other GM code has the 2 items tied together. This works out and can improve highway mileage 10% or more.
RBob.
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i don't know how the 747 does it, but in 730 8D the ECM stays in closed loop & learn control is disabled during hiway mode, also the O2 sensor voltage drops low & target AFR goes above 14.73.
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Re: 7747 lean hiway cruise patch...a few q's...
Hwy mode in the 7747 was of great interest to me, since my milage sucks on a good day.
From what I can see, and having stepped through the hac looking for it, the 7747 ONLY advances spark. It's still chasing 14.7 AFR. Someone, please correct me if I'm wrong, but watching it as I run down the road, the only thing I see, is an instant advance as it goes in, and an instant retard as it goes out. The BLM, INT, and O2 still chase just as they do otherwise. Initially, I added 1-2 degrees. Got as far as adding 8. Saw no improvement in milage. Did see knock counts. ( 49 degrees total is a lot of spark, even for this ancient slow-burn big block )
Lean cruise is THE reason my truck now sports an 8746. That one has a fuel table I can play with. No real progress, yet, but.....
As RBob suggests, my in-cylinder preassure readings suggest that hiway mode and lean burn isn't a result of advanced spark. Lean burn requires more advance. Not the other way around.
From what I can see, and having stepped through the hac looking for it, the 7747 ONLY advances spark. It's still chasing 14.7 AFR. Someone, please correct me if I'm wrong, but watching it as I run down the road, the only thing I see, is an instant advance as it goes in, and an instant retard as it goes out. The BLM, INT, and O2 still chase just as they do otherwise. Initially, I added 1-2 degrees. Got as far as adding 8. Saw no improvement in milage. Did see knock counts. ( 49 degrees total is a lot of spark, even for this ancient slow-burn big block )
Lean cruise is THE reason my truck now sports an 8746. That one has a fuel table I can play with. No real progress, yet, but.....
As RBob suggests, my in-cylinder preassure readings suggest that hiway mode and lean burn isn't a result of advanced spark. Lean burn requires more advance. Not the other way around.
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