47 lines
2.6 KiB
Markdown
47 lines
2.6 KiB
Markdown
# Saab B205 with GT17 and ECU boost control
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The desktop Saab menu entry and `--scenario b205` now select an estimated GT1752
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turbo configuration. `--turbo gt17` makes that choice explicit; `--turbo none`
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selects the previous naturally aspirated baseline. CLI and WAV capture follow
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the same defaults. `SaabB205Scenario` preserves its baseline API;
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`SaabTurboScenario` is the boosted convenience class.
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The GT17 calibration uses a 26 mm compressor tip radius, 19 mm effective turbine
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radius, 2e-5 kg m² rotor inertia, 420/350 mm² effective compressor/turbine areas,
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70% efficiencies, 100 cc housing volumes and a 24 mm wastegate. These are model
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estimates, not a measured Saab map or verified rotor inertia. The Garrett catalog
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identifies the Saab GT1752 application:
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https://www.turbomaster.info/eng/downloads/catalog_garrett.pdf
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The ECU requests up to 45 kPa gauge boost, ramping with pedal and RPM. A PI
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controller uses manifold pressure filtered over 50 ms, conditional integration,
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and bounded pneumatic bleed duty (0–85%). Duty reduces the pressure signal to
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the existing spring/diaphragm actuator. Actual valve travel remains damped and
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boost emerges from the physical rotor, restrictions and conserved gas transfers.
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Zero duty restores the mechanical pressure-can response; it does not forcibly
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open the valve or impose a manifold pressure. Targets below spring boost cannot
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be achieved by wastegate bleed alone.
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Lift-off, fuel cut and invalid sensor data request zero duty and clear the PI
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integral. Invalid boost sensors cut fuel. Manifold or charge pressure above
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75 kPa gauge triggers fuel cut, recovering below 55 kPa gauge. This is a basic
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estimated safety calibration, not a reproduction of Saab Trionic software.
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No intercooler, compressor surge/BOV model or knock model has been added;
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charge heating and exhaust backpressure remain present.
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The regression holds the engine at 3,500 RPM, applies full pedal for six seconds,
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then releases for three. It checks boost settling within 8 kPa of the 45 kPa
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target, shaft spool-up/down, finite audio, no pipe positivity repairs, no housing
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donor limiting, and gas/rotor energy residual below 0.1 J. Controller checks cover
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overboost, recovery, pedal release and an invalid sensor. The HUD shows target
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gauge boost, actuator bleed duty, turbo RPM and absolute gas pressures.
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```sh
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cmake --build build-desktop --target fluidsim_desktop -j4
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./build-desktop/fluidsim_desktop --scenario b205 --turbo gt17
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./build-audit/fluidsim_scenario_benchmark 6 loaded b205-gt17
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```
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All ten CTest suites pass, including the new ten-second Saab turbo regression.
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The GT17 benchmark holds 5,500 RPM, below the Saab's 6,500 RPM limiter.
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