# Engine audio launch response, r315

## Source recording check

The 240SX acceleration recording loaded by the packaged viewer is byte-identical
to the file in the XP game installation:

| Use | File | SHA-256 |
|---|---|---|
| throttle/acceleration | `GIN_Nissan_240SX.gin` | `4f0881943a13f09185047184a63b7eab264780c518d9c08a3f033ef5f5ab77d9` |
| coast/deceleration | `GIN_240SX_Decel.gin` | `a594eaa9bd9887d36d7d224b1c6ace0963e4677a0338fb476ed5b023106ab469` |

Both packaged files match the XP installation byte-for-byte. The coast
recording is used when the stock 240SX throttle command is released.

## Launch behavior

In the packaged r314 viewer, a 240SX W hold began from rest at 800 RPM. After
250 ms the car had reached 0.16 m/s while the engine remained at 800 RPM; after
one second it reached 1.68 m/s and still remained at 800 RPM. The Ginsu
acceleration sample starts at 1,526.5 RPM, so the viewer was stretching its
lowest sample far below its recorded range during the launch.

Revision r315 lets the engine climb under throttle while the car is below
8 m/s, then blends back to RPM calculated from the selected stock gear ratio,
final drive, and wheel radius. The launch target uses the stock idle RPM and
first shift threshold, with a 45% span as a preview clutch-slip estimate. RPM
approaches its target over time rather than jumping immediately. During a
matched Chrome W hold from the same route start, the values were:

| Time after W | Speed | Engine RPM |
|---:|---:|---:|
| 0 ms | 0 m/s | 800 |
| 250 ms | 0.19 m/s | 1,549 |
| 1 s | 1.65 m/s | 2,812 |
| 2 s | 4.34 m/s | 2,513 |

The packaged AudioWorklet reported `running`, selected
`GIN_Nissan_240SX.gin` for acceleration and `GIN_240SX_Decel.gin` for coast,
and received the live RPM and throttle values.

This corrects the viewer's silent-sounding standing launch. The 8 m/s blend
range, 45% launch span, and smoothing rates are not recovered retail constants.
The XP disk currently stops at the account login, so this is not a comparison
against live retail RPM or audio behavior. The visible result is in review
capture 396; open the packaged viewer from that entry and drive with W to hear
the same engine path.