uhryniuk
80c9373ded
The NO-SAI-NO-O2 reference map bundles SAI + O2 + airbox deletes, so it validates the three flag bytes as a GROUP but doesn't isolate O2 individually; no single-mod map exists and the x.a() device-layout branch for this ECU is too nested to trace. - SAI @ 0x53801: confirmed (code lc() -> Devices[0] via fe[33], + the delete map). - O2 @ 0x53818/0x53819: probable (2 O2 sensors declared off <-> 2 adjacent bytes cleared; 865 has no air-flap so airbox removal is fuel-only). Viewer now shows confirmed/probable badges and a warning that flags alone are not a tune: O2 delete forces open-loop and needs fuel enrichment, so prefer flashing a complete matching delete map over hand-toggling a stock one. See DEVICES.md.
69 lines
3.2 KiB
Markdown
69 lines
3.2 KiB
Markdown
# Device-enable flags (SAI / O2 / lambda) — validated
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## How they were found
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Both stock reference maps (20187, 20188) have SAI and O2 **active**, so diffing
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them can't reveal the delete flags. The confirmation came from a community map
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that explicitly disables them:
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`20188Map2009AIRBOXBONNY.hex` — "Bonneville, aftermarket exhaust, mechanical
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odometer, NO AIR BOX, K&N, British Custom mufflers, **NO SAI, NO O² SENSORS**".
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Same base as stock 20188, so the diff isolates the deletes.
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Diff (flat ROM) of that map vs stock 20188 = 0.36%, split into:
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- the fuel tables (airbox/K&N enrichment — expected), and
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- a small cluster in the device-config region at **0x53801…0x53819**.
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## The flags
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They are a **byte-boolean array** at flat-ROM `base + fe[33]` (= `0x50000 + 0x3801
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= 0x53801`), one byte per device, **1 = enabled, 0 = disabled**.
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The delete map changed exactly three bytes from 1 → 0:
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| Flat-ROM offset | Stock | Deleted | Device |
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|---|---|---|---|
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| `0x53801` | 1 | 0 | **SAI** (Secondary Air Injection) |
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| `0x53818` | 1 | 0 | **O2 sensor** |
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| `0x53819` | 1 | 0 | **O2 sensor (2)** |
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SAI is the first flag in the array; the two O2 sensors are the last two —
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consistent with the `Devices` resource order (SAI = index 0; O2 Sensor / O2
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Sensor (2)). The three-byte change matching "NO SAI, NO O²" is unambiguous.
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To disable a device: set its byte to `0`. (The `0x5369C`/`0x536AB` bytes that
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also changed are idle/open-loop trim that comes with removing the O2 feedback,
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not device-enable flags.)
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## Editing / export
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The downloaded `.hex` format's integrity is the `dc` stream cipher + the unpack
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directory; the `caXX` bytes in the header/tail are map-ID metadata, **not** a
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calibration checksum. So a device toggle = flip the byte in the flat ROM, re-pack
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to the decoded layout, and `dc`-encode back to `.hex`. (The separate *ECU flash*
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checksum is computed at flash time and is out of scope for the read/edit tool.)
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## Confidence
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- **SAI = 0x53801: ~90% (high).** Two independent confirmations: the device-name
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logic in `l.java` `lc()` resolves `Devices[0]=SAI` via `fe[33]` to exactly
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0x53801, AND the real NO-SAI map cleared precisely that byte.
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- **O2 sensors = 0x53818 / 0x53819: ~80% (probable).** The map declares "NO O²
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SENSORS" (the twin has two) and exactly two adjacent boolean bytes cleared
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beyond SAI; the 865 has no air-flap, so airbox removal is fuel-only (no flag).
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Not independently isolated — no single-mod reference map exists, and the exact
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`x.a()` device-layout branch for this ECU (i27=72) is too deeply nested to
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trace reliably.
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## The real-world caveat (more important than the labels)
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Correct flags are **not** a good tune by themselves. Disabling O2 forces the ECU
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**open-loop**: it stops live fuel trim and runs entirely on the base fuel map.
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Stock maps assume closed-loop trim at idle/cruise, so an O2-delete on an otherwise
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stock map can run lean/rough. A proper delete pairs flags-off with fuel enrichment
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(which is exactly why the AIRBOXBONNY reference map also changed the fuel tables).
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**Recommendation:** flash a complete, known-good delete map matching the hardware
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(exhaust/filters), not hand-toggled flags on a stock map. The checkbox editor is
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for understanding/building a map, not a one-click safe delete.
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