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#1 |
![]() Join Date: Jan 2024
Location: Boston, MA
Posts: 170
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Doing a binary comparison on BMCB and the BMCB-based chip in my car at the moment, there's a few differences unaccounted for in the XDF I'm using.
Values below are in hex. Address / Stock BMCB / Mine 0006 / FF / 89 0007 / C9 / 1D 06FB / 50 / 00 06FE / 50 / 00 33BC / 14 / 15 3EDC / 4E / 00 3EDD / 04 / 00 3EDE / 0F / 00 3EDF / BD / 00 After a little research, it appears 0006-0007 are a 2-byte checksum. These bytes are different in each variation of a BMCB file I open or make changes to. There's a lot of stuff stored in the 06A0-0700 range overall, so it seems likely 06FB and 06FE have some kind of 1-byte purpose as they're buried in between other values. Some of their neighbors are.... 06DA: Speed Threshold To Disable + Reset CARS 06DB: Vehicle Speed Threshold To Enable CARS 06DC: Vehicle Speed Threshold To Disable CARS 06DD: RPM Threshold To Enable CARS 06DE: % TPS Threshold To Disable CARS 06FB: ??? 06FC: Cool. Temp Port Throt. Disable Threshold 06FD: Cool. Temp Port Throt. Enable Threshold 06FE: ??? 06FF: Oil Temp Port Throt. Disable Threshold 0700: Oil Temp Port Throt. Enable Threshold 0705: Minimum Counts for Valet Switch Open 0706: Minimum Counts for Valet Switch Closed The last four being in a row makes me think it's some kind of table. I assume one of these unknowns enables FULL mode by default, since my car does go into FULL mode at ignition key on. ![]() |
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#2 |
Join Date: Aug 2005
Location: Fishers, IN
Posts: 809
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Remember, those raw addresses all start a 0x8000h.
Code:
86FB 86FB KPTCOOL PORT THROTTLE ENABLE MIN COOL TEMP 86FC 86FC KPTHCOLD PORT THROTTLE DISABLE MAX COOL TEMP 86FD 86FD KPTHCOLR PORT THROTTLE RE-ENABLE COOL TEMP 86FE 86FE KPTLOTE PORT THROTTLE ENABLE MIN OIL TEMP 86FF 86FF KPTHOTD PORT THROTTLE DISABLE MAX OIL TEMP 8700 8700 KPTHOTR PORT THROTTLE RE-ENABLE OIL TEMP 8701 8701 KPTVOLT PORT THROTTLE ENABLE MIN VOLTAGE 8702 8702 KPTVOLTH PORT THROTTLE VOLTAGE HYSTERESIS B3BC: This is the byte change that causes the program to startup in full power mode BEDC and BEDD: This is part of the EST (spark timing) minor loop. Changing 0x4E to 0x00 is totally odd. It's a BCLR command (the bit to clear is EST enable), in the event that the stall saver logic is active. I would not recommend that change. In effect, whoever made that change is keeping EST spark control active while the engine is in stall saver mode. BEDE: Same routine as above. The 0x0F is an instruction to set a program interrupt, which is supposed to happen at that point. I would not make that change. BEDF: the 0x45 is an instruction (JSR=Jump to Subroutine) which is supposed to happen next. That subroutine sends a command to another chipset on the board. WTH were they trying to accomplish by changing that to 0x00? Not a good idea, IMO. I can only suspect they were changing these bytes to sort of leave a "marker" to identify their calibration somehow. Without understanding what was there.
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#3 | |
Join Date: Aug 2005
Location: Fishers, IN
Posts: 809
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CCP - canister purge variables Fan variables A/C IAC AIR Pump Secondary fuel pump and CARS as you already pointed out
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Todd ____________________________________ *** our email address has changed! info@pepmeierengines.com pepmeierengines.com Friend us on Facebook too: www.facebook.com/profile.php?id=100011443683384 Pepmeier Engine Development |
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#4 | |
![]() Join Date: Jan 2024
Location: Boston, MA
Posts: 170
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Todd, thank you so much for that insight. I may put these back to stock and see how the car reacts. I have two anomalies I haven't had time to chase yet. 1) When cold it loves to stall when coming to a stop and sometimes is hard to restart. I've been attributing (excusing it...) to being a modified LT5, but maybe there's more to this than meets the eye. 2) In a high gear situation (e.g., puttering along at 70MPH in 6th) subtle increases to the throttle to pass someone gradually or when going up a hill sometimes causes the car to feel like it "shuts off" for lack of better terms. Power is immediately gone as if someone snapped the throttle shut or killed the injectors. If I drop a gear and get it to a lower load it immediately goes back to normal. I've been meaning to datalog while in these conditions to see if it's a certain combination that triggers whatever it is. Thanks again, I appreciate sharing your knowledge on the addresses. -Brian |
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