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verification/SAAB_GT17.md

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