set a default, detect error (#4504)

firmware/controllers/algo/defaults/default_fuel.cpp

@@ -271,4 +271,7 @@ void setDefaultFuel() {
 
 	// TPS/TPS AE curve
 	setMazdaMiataNbTpsTps();
+
+	// Some reasonable reference pressure that many vehicles use
+	engineConfiguration->fuelReferencePressure = 300;
 }

firmware/controllers/algo/fuel/injector_model.cpp

@@ -39,6 +39,14 @@ float InjectorModel::getInjectorFlowRatio() {
 	}
 
 	float referencePressure = engineConfiguration->fuelReferencePressure;
+
+	if (referencePressure < 50) {
+		// impossibly low fuel ref pressure
+		firmwareError(OBD_PCM_Processor_Fault, "Impossible fuel reference pressure: %f", referencePressure);
+
+		return 1.0f;
+	}
+
 	expected<float> absRailPressure = getAbsoluteRailPressure();
 
 	// If sensor failed, best we can do is disable correction

firmware/integration/rusefi_config.txt

@@ -1270,7 +1270,7 @@ tle8888_mode_e tle8888mode;
 	injector_compensation_mode_e injectorCompensationMode;+None = I have a MAP-referenced fuel pressure regulator\nFixed rail pressure = I have an atmosphere-referenced fuel pressure regulator (returnless, typically)\nSensed rail pressure = I have a fuel pressure sensor;
 
 	pin_output_mode_e fan2PinMode;
-	float fuelReferencePressure;+This is the pressure at which your injector flow is known.\nFor example if your injectors flow 400cc/min at 3.5 bar, enter 350kpa here.;"kPa", 1, 0, 0, 700000, 0
+	float fuelReferencePressure;+This is the pressure at which your injector flow is known.\nFor example if your injectors flow 400cc/min at 3.5 bar, enter 350kpa here.;"kPa", 1, 0, 50, 700000, 0
 	float postCrankingFactor;+Fuel multiplier (enrichment) immediately after engine start;"mult", 1, 0, 1, 3, 2
 	float postCrankingDurationSec;+Time over which to taper out after start enrichment;"seconds", 1, 0, 0, 30, 0
 	ThermistorConf auxTempSensor1