uhryniuk
f830f8937d
New research/ROAD_TEST_LOG.md: the 2026-09-15 flash of 20262-arrow-delete-lowthrottle-composed.hex was a major real-world success (stalling fully resolved, decel backfire much reduced but not eliminated). Captures the live diagnostic reasoning that followed: correcting an overly-lean-leaning framing mid-session (residual decel pop is more likely a rich-unburned-mixture-with-no-SAI-assist problem, not a lean one), a structural hypothesis that the Idle Fuel Trim (CO) curve likely applies whenever the throttle is closed at any RPM rather than only at a literal stop (only 2 of its 32 points are currently corrected, and the untouched middle range lines up with the residual pop's RPM window), and the reasoning for rejecting airbox-baffle removal as a fix for decel popping specifically (wrong mechanism -- closed throttle isn't airbox-limited -- and risks worsening the separately-flagged, still unaddressed main-VE-table leanness gap). Also updates TABLES.md with the CO-trim applicability open question, and brings TUNING_GUIDE.md's "local research assets" section up to date (it still said maps were gitignored/unflashable, both stale). Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01FP2GaxS9HkUdL5sLBnjKje
122 lines
6.5 KiB
Markdown
122 lines
6.5 KiB
Markdown
# Road test log — real-world tune results
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Empirical outcomes from actually flashing and riding, kept separate from the
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static reverse-engineering docs (`TABLES.md`, `DEVICES.md`) since this is
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field data, not derived facts about the ROM format.
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## 2026-09-15 — `20262-arrow-delete-lowthrottle-composed.hex`, first real ride
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Flashed after several days running plain stock `20262Map.hex` (SAI/O2 flags
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still enabled despite SAI being physically removed, snorkel already removed
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with zero main-table correction). Result: **major, immediate improvement.**
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- **Stalling at lights / low-speed choking: fully resolved.** Not just
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fixed — noticeably *better* than expected: "a lot more low rev and slow
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speed control," easier to get going, smooth at slow speeds. Attributed to
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the Low-throttle fuel table correction (under ~10% throttle, both
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cylinders, +7% to +24%) plus the two corrected Idle Fuel Trim (CO) points.
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- **Decel backfire (3-4.5k RPM, 2nd-4th gear): dramatically better, not
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eliminated.** Before: "backfires like crazy," reliably reproducible.
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After: 1-3 noticeable pops on a 5k→3k decel sweep in 2nd-3rd gear, and
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*not* reliably reproducible anymore (sometimes it doesn't happen at all).
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- **New/newly-noticeable, minor**: holding steady revs at 5k, the engine
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can "break up and get a tiny bit throaty." Described as minor, not
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concerning, bike is very rideable as-is.
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**User's own assessment**: "In the current state I could drive it as is and
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be happy" — this is a real, working baseline, not a stopgap.
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## Diagnosing the residual decel pop — reasoning, 2026-09-15/16
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Two mechanisms were on the table for residual exhaust-side popping on
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deceleration:
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1. **Rich unburned mixture reaching the hot exhaust with no SAI assist to
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burn it cleanly** — the classic mechanism for popping *from the exhaust*
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on decel (as opposed to backfiring through the intake, which is the
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lean-misfire pattern). SAI's actual job was adding oxygen downstream to
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assist combustion of that charge; a fuel table can't replicate an air
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*supply* by adjusting how much fuel goes in. **This is the mechanism the
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user's own reasoning correctly pointed at** (session correction:
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"I mean it's still rich, since that's what caused the popping" — right
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call, corrected an overly-lean-leaning framing from earlier in the same
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conversation).
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2. Unaddressed leanness in areas the current composed file doesn't touch.
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**Important structural correction, made mid-session**: the Idle Fuel Trim
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(CO) table (`0x53690`-`0x536AF`, 32 RPM-indexed points, same RPM axis as
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the main tables — see `TABLES.md`) was initially assumed to apply only at a
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literal stop. That's likely wrong. The table has real entries all the way
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out to 10,000 RPM — no reason for that range to exist if it only ever
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applied near idle. **More likely: this curve applies whenever the throttle
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is closed/near-closed, at whatever RPM the engine happens to be at** — i.e.
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it's the relevant table during an active decel sweep through elevated RPM,
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not just idle-at-a-stop.
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Given that, the composed file's coverage of this curve matters directly for
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the decel-popping symptom:
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| Curve region | RPM range | Correction status |
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| Point 12 | 2400 | **Corrected** (see `compose_arrow_delete.py`) |
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| Points 13-26 | 2600-6500 | **Untouched** — still Arrow's original values |
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| Point 27 | 7000 | **Corrected** |
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The user's actual decel sweep (5000→3000 RPM) runs almost entirely through
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the **untouched middle section** of this curve. That's a more precise,
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evidence-grounded candidate for the residual pop than either "lean the
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idle" (don't — that's the low-throttle fix that's working great, protect
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it) or "richen the higher range" broadly (that's a different symptom,
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different table — see below).
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**Two symptoms, two different tables — don't conflate them:**
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| Symptom | Condition | Likely table |
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|---|---|---|
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| Decel pop | closed throttle, elevated RPM (falling through 3-5k) | Idle Fuel Trim (CO) curve, untouched middle points |
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| "Breaks up/throaty" at held 5k revs | open throttle, sustained load | Main VE fuel tables — still 100% stock-Arrow, unaddressed |
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The second one is the known, previously-flagged gap (no main-table
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correction exists for the snorkel/baffle removal). It is a *separate*
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project from the decel-pop investigation, not the same fix.
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## Baffle removal considered and rejected as a fix for decel pop (2026-09-16)
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User proposed removing the airbox internal baffle (on top of already-removed
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snorkel), reasoning more airflow would "even out" the remaining popping.
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**Rejected, reasoning below** — not because baffle removal is bad in
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general, but because it's the wrong tool for this specific symptom:
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- Decel popping happens at **closed throttle**, where the throttle plate
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itself (not the airbox) is the dominant restriction. Baffle removal
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doesn't meaningfully change airflow in that condition.
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- Baffle removal *does* increase airflow at every **open**-throttle
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condition — exactly the untouched main VE tables. This widens the
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existing, already-flagged leanness gap rather than closing it, and is
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likely to make the "breaks up/throaty at 5k" symptom *worse*, not better.
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- Per `COMMUNITY_TUNING.md`'s TTP dyno data, baffle-removal+2-1 already
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lands close to *full* airbox removal in airflow/power terms. Pulling the
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baffle on top of an already-removed snorkel pushes past what either
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reference data point in this project actually characterizes.
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**Recommendation given**: don't pursue baffle removal as a decel-pop fix.
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If pursued later for its own sake (more performance), it should come
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*with* main-table correction work, not before it.
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## Where this leaves things, if picked up again
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Current file (`derived/20262-arrow-delete-lowthrottle-composed.hex`) is a
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good, real, working baseline — user is happy running it as-is. If further
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work is wanted:
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1. **For the decel pop specifically**: pull real reference deltas for the
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untouched CO-trim points in the 2600-6500 RPM range (same source
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methodology as the rest of this project — `20184dynoTuneSteveO2-Disable.hex`
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vs `20186Map.hex`), test in isolation, don't touch the low-throttle
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fix that's already working.
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2. **For the main-table gap**: the bigger, separately-tracked project —
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full VE-table composition for the snorkel/airbox-baffle removal, still
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not started (`COMMUNITY_TUNING.md`'s "~1340-byte main VE overlap").
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3. Neither is urgent — current state is rideable and the user is satisfied
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with it. This is optimization, not a fix for something broken.
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