]> git.mxchange.org Git - flightgear.git/blobdiff - src/FDM/JSBSim/FGPiston.cpp
Sync. with JSBSim CVS.
[flightgear.git] / src / FDM / JSBSim / FGPiston.cpp
index 805200f18025037ef561f4ea51f3a6fd60a3635e..263591e48b7baeaab9843b5e9d1739a2a23ae316 100644 (file)
@@ -1,7 +1,8 @@
 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
  Module:       FGPiston.cpp
- Author:       Jon S. Berndt
+ Author:       Jon S. Berndt, JSBSim framework
+               Dave Luff, Piston engine model
  Date started: 09/12/2000
  Purpose:      This module models a Piston engine
 
@@ -38,84 +39,546 @@ HISTORY
 INCLUDES
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
 
-#include "FGDefs.h"
 #include "FGPiston.h"
+#include "FGPropulsion.h"
+
+namespace JSBSim {
 
 static const char *IdSrc = "$Id$";
 static const char *IdHdr = ID_PISTON;
 
-extern short debug_lvl;
-
 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 CLASS IMPLEMENTATION
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
 
-FGPiston::FGPiston(FGFDMExec* exec, FGConfigFile* Eng_cfg) : FGEngine(exec)
+FGPiston::FGPiston(FGFDMExec* exec, FGConfigFile* Eng_cfg) : FGEngine(exec),
+  R_air(287.3),
+  rho_fuel(800),                 // estimate
+  calorific_value_fuel(47.3e6),
+  Cp_air(1005),
+  Cp_fuel(1700)
 {
   string token;
 
+  Type = etPiston;
+  crank_counter = 0;
+  EngineNumber = 0;
+  OilTemp_degK = 298;
+  MinManifoldPressure_inHg = 6.5;
+  MaxManifoldPressure_inHg = 28.5;
+  ManifoldPressure_inHg = Atmosphere->GetPressure() * psftoinhg; // psf to in Hg
+  CylinderHeadTemp_degK = 0.0;
+  Displacement = 360;
+  MaxHP = 200;
+  Cycles = 2;
+  IdleRPM = 600;
+  Magnetos = 0;
+  ExhaustGasTemp_degK = 0.0;
+  EGT_degC = 0.0;
+
+  dt = State->Getdt();
+
+  // Initialisation
+  volumetric_efficiency = 0.8;  // Actually f(speed, load) but this will get us running
+
+  // First column is thi, second is neta (combustion efficiency)
+  Lookup_Combustion_Efficiency = new FGTable(12);
+  *Lookup_Combustion_Efficiency << 0.00 << 0.980;
+  *Lookup_Combustion_Efficiency << 0.90 << 0.980;
+  *Lookup_Combustion_Efficiency << 1.00 << 0.970;
+  *Lookup_Combustion_Efficiency << 1.05 << 0.950;
+  *Lookup_Combustion_Efficiency << 1.10 << 0.900;
+  *Lookup_Combustion_Efficiency << 1.15 << 0.850;
+  *Lookup_Combustion_Efficiency << 1.20 << 0.790;
+  *Lookup_Combustion_Efficiency << 1.30 << 0.700;
+  *Lookup_Combustion_Efficiency << 1.40 << 0.630;
+  *Lookup_Combustion_Efficiency << 1.50 << 0.570;
+  *Lookup_Combustion_Efficiency << 1.60 << 0.525;
+  *Lookup_Combustion_Efficiency << 2.00 << 0.345;
+
+  Power_Mixture_Correlation = new FGTable(13);
+  *Power_Mixture_Correlation << (14.7/1.6) << 78.0;
+  *Power_Mixture_Correlation << 10 <<  86.0;
+  *Power_Mixture_Correlation << 11 <<  93.5;
+  *Power_Mixture_Correlation << 12 <<  98.0;
+  *Power_Mixture_Correlation << 13 << 100.0;
+  *Power_Mixture_Correlation << 14 <<  99.0;
+  *Power_Mixture_Correlation << 15 <<  96.4;
+  *Power_Mixture_Correlation << 16 <<  92.5;
+  *Power_Mixture_Correlation << 17 <<  88.0;
+  *Power_Mixture_Correlation << 18 <<  83.0;
+  *Power_Mixture_Correlation << 19 <<  78.5;
+  *Power_Mixture_Correlation << 20 <<  74.0;
+  *Power_Mixture_Correlation << (14.7/0.6) << 58;
+
   Name = Eng_cfg->GetValue("NAME");
   Eng_cfg->GetNextConfigLine();
-  while (Eng_cfg->GetValue() != "/FG_PISTON") {
+  while (Eng_cfg->GetValue() != string("/FG_PISTON")) {
     *Eng_cfg >> token;
-    if      (token == "BRAKEHORSEPOWER") *Eng_cfg >> BrakeHorsePower;
-    else if (token == "MAXTHROTTLE")     *Eng_cfg >> MaxThrottle;
-    else if (token == "MINTHROTTLE")     *Eng_cfg >> MinThrottle;
-    else if (token == "SLFUELFLOWMAX")   *Eng_cfg >> SLFuelFlowMax;
-    else if (token == "SPEEDSLOPE")      *Eng_cfg >> SpeedSlope;
-    else if (token == "SPEEDINTERCEPT")  *Eng_cfg >> SpeedIntercept;
-    else if (token == "ALTITUDESLOPE")   *Eng_cfg >> AltitudeSlope;
+    if      (token == "MINMP") *Eng_cfg >> MinManifoldPressure_inHg;
+    else if (token == "MAXMP") *Eng_cfg >> MaxManifoldPressure_inHg;
+    else if (token == "DISPLACEMENT") *Eng_cfg >> Displacement;
+    else if (token == "MAXHP") *Eng_cfg >> MaxHP;
+    else if (token == "CYCLES") *Eng_cfg >> Cycles;
+    else if (token == "IDLERPM") *Eng_cfg >> IdleRPM;
+    else if (token == "MAXTHROTTLE") *Eng_cfg >> MaxThrottle;
+    else if (token == "MINTHROTTLE") *Eng_cfg >> MinThrottle;
     else cerr << "Unhandled token in Engine config file: " << token << endl;
   }
 
-  if (debug_lvl > 0) {
-    cout << "\n    Engine Name: " << Name << endl;
-    cout << "      BrakeHorsePower = " << BrakeHorsePower << endl;
-    cout << "      MaxThrottle = " << MaxThrottle << endl;
-    cout << "      MinThrottle = " << MinThrottle << endl;
-    cout << "      SLFuelFlowMax = " << SLFuelFlowMax << endl;
-    cout << "      SpeedSlope = " << SpeedSlope << endl;
-    cout << "      SpeedIntercept = " << SpeedIntercept << endl;
-    cout << "      AltitudeSlope = " << AltitudeSlope << endl;
+  Debug(0); // Call Debug() routine from constructor if needed
+}
+
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+FGPiston::~FGPiston()
+{
+  Debug(1); // Call Debug() routine from constructor if needed
+}
+
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+double FGPiston::Calculate(double PowerRequired)
+{
+  if (FuelFlow_gph > 0.0) ConsumeFuel();
+
+  Throttle = FCS->GetThrottlePos(EngineNumber);
+  Mixture = FCS->GetMixturePos(EngineNumber);
+
+  //
+  // Input values.
+  //
+
+  p_amb = Atmosphere->GetPressure() * 48;              // convert from lbs/ft2 to Pa
+  p_amb_sea_level = Atmosphere->GetPressureSL() * 48;
+  T_amb = Atmosphere->GetTemperature() * (5.0 / 9.0);  // convert from Rankine to Kelvin
+
+  RPM = Propulsion->GetThruster(EngineNumber)->GetRPM() *
+        Propulsion->GetThruster(EngineNumber)->GetGearRatio();
+    
+  IAS = Auxiliary->GetVcalibratedKTS();
+
+    doEngineStartup();
+    doManifoldPressure();
+    doAirFlow();
+    doFuelFlow();
+
+  //Now that the fuel flow is done check if the mixture is too lean to run the engine
+  //Assume lean limit at 22 AFR for now - thats a thi of 0.668
+  //This might be a bit generous, but since there's currently no audiable warning of impending
+  //cutout in the form of misfiring and/or rough running its probably reasonable for now.
+  if (equivalence_ratio < 0.668)
+    Running = false;
+
+  doEnginePower();
+    doEGT();
+    doCHT();
+    doOilTemperature();
+    doOilPressure();
+
+  PowerAvailable = (HP * hptoftlbssec) - PowerRequired;
+  return PowerAvailable;
+}
+
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+/**
+ * Start or stop the engine.
+ */
+
+void FGPiston::doEngineStartup(void)
+{
+  // Check parameters that may alter the operating state of the engine. 
+  // (spark, fuel, starter motor etc)
+  bool spark;
+  bool fuel;
+
+  // Check for spark
+  Magneto_Left = false;
+  Magneto_Right = false;
+  // Magneto positions:
+  // 0 -> off
+  // 1 -> left only
+  // 2 -> right only
+  // 3 -> both
+  if (Magnetos != 0) {
+    spark = true;
+  } else {
+    spark = false;
+  }  // neglects battery voltage, master on switch, etc for now.
+  
+  if ((Magnetos == 1) || (Magnetos > 2)) Magneto_Left = true;
+  if (Magnetos > 1)  Magneto_Right = true;
+
+  // Assume we have fuel for now
+  fuel = !Starved;
+
+  // Check if we are turning the starter motor
+  if (Cranking != Starter) {
+    // This check saves .../cranking from getting updated every loop - they
+    // only update when changed.
+    Cranking = Starter;
+    crank_counter = 0;
   }
 
-  Type = etPiston;
-  EngineNumber = 0;
+  if (Cranking) crank_counter++;  //Check mode of engine operation
+  
+  if (!Running && spark && fuel) {  // start the engine if revs high enough
+    if (Cranking) {
+      if ((RPM > 450) && (crank_counter > 175)) // Add a little delay to startup
+        Running = true;                         // on the starter
+    } else {
+      if (RPM > 450)                            // This allows us to in-air start
+        Running = true;                         // when windmilling
+    }
+  }
+
+  // Cut the engine *power* - Note: the engine may continue to
+  // spin if the prop is in a moving airstream
 
-  if (debug_lvl & 2) cout << "Instantiated: FGPiston" << endl;
+  if ( Running && (!spark || !fuel) ) Running = false;
+
+  // Check for stalling (RPM = 0).
+  if (Running) { 
+    if (RPM == 0) {
+      Running = false;
+    } else if ((RPM <= 480) && (Cranking)) {
+      Running = false;
+    }
+  }
 }
 
 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
-FGPiston::~FGPiston()
+/**
+ * Calculate the nominal manifold pressure in inches hg
+ *
+ * This function calculates nominal manifold pressure directly
+ * from the throttle position, and does not adjust it for the
+ * difference between the pressure at sea level and the pressure
+ * at the current altitude (that adjustment takes place in
+ * {@link #doEnginePower}).
+ *
+ * TODO: changes in MP should not be instantaneous -- introduce
+ * a lag between throttle changes and MP changes, to allow pressure
+ * to build up or disperse.
+ *
+ * Inputs: MinManifoldPressure_inHg, MaxManifoldPressure_inHg, Throttle
+ *
+ * Outputs: ManifoldPressure_inHg
+ */
+
+void FGPiston::doManifoldPressure(void)
 {
-  if (debug_lvl & 2) cout << "Destroyed:    FGPiston" << endl;
+  if (Running || Cranking) {
+    ManifoldPressure_inHg = MinManifoldPressure_inHg +
+            (Throttle * (MaxManifoldPressure_inHg - MinManifoldPressure_inHg));
+  } else {
+    ManifoldPressure_inHg = Atmosphere->GetPressure() * psftoinhg; // psf to in Hg
+  }  
 }
 
 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+/**
+ * Calculate the air flow through the engine.
+ *
+ * At this point, ManifoldPressure_inHg still represents the sea-level
+ * MP, not adjusted for altitude.
+ *
+ * Inputs: p_amb, R_air, T_amb, ManifoldPressure_inHg, Displacement,
+ *   RPM, volumetric_efficiency
+ *
+ * Outputs: rho_air, m_dot_air
+ */
 
-float FGPiston::Calculate(float PowerRequired)
+void FGPiston::doAirFlow(void)
 {
-  float h,EngineMaxPower;
+  rho_air = p_amb / (R_air * T_amb);
+  double rho_air_manifold = rho_air * ManifoldPressure_inHg / 29.6;
+  double displacement_SI = Displacement * in3tom3;
+  double swept_volume = (displacement_SI * (RPM/60)) / 2;
+  double v_dot_air = swept_volume * volumetric_efficiency;
+  m_dot_air = v_dot_air * rho_air_manifold;
+}
 
-  ConsumeFuel();
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+/**
+ * Calculate the fuel flow into the engine.
+ *
+ * Inputs: Mixture, thi_sea_level, p_amb_sea_level, p_amb, m_dot_air
+ *
+ * Outputs: equivalence_ratio, m_dot_fuel
+ */
 
-  Throttle = FCS->GetThrottlePos(EngineNumber);
+void FGPiston::doFuelFlow(void)
+{
+  double thi_sea_level = 1.3 * Mixture;
+  equivalence_ratio = thi_sea_level * p_amb_sea_level / p_amb;
+  m_dot_fuel = m_dot_air / 14.7 * equivalence_ratio;
+  FuelFlow_gph = m_dot_fuel
+    * 3600                     // seconds to hours
+    * 2.2046                   // kg to lb
+    / 6.6;                     // lb to gal_us of kerosene
+}
+
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+/**
+ * Calculate the power produced by the engine.
+ *
+ * Currently, the JSBSim propellor model does not allow the
+ * engine to produce enough RPMs to get up to a high horsepower.
+ * When tested with sufficient RPM, it has no trouble reaching
+ * 200HP.
+ *
+ * Inputs: ManifoldPressure_inHg, p_amb, p_amb_sea_level, RPM, T_amb, 
+ *   equivalence_ratio, Cycles, MaxHP
+ *
+ * Outputs: Percentage_Power, HP
+ */
 
-  h = Position->Geth();
+void FGPiston::doEnginePower(void)
+{
+  ManifoldPressure_inHg *= p_amb / p_amb_sea_level;
 
-  if (h < 0) h = 0;
+  if (Running) {       
+    double ManXRPM = ManifoldPressure_inHg * RPM;
+    double T_amb_degF = KelvinToFahrenheit(T_amb);
+    double T_amb_sea_lev_degF = KelvinToFahrenheit(288); 
 
-  EngineMaxPower = (1 + AltitudeSlope*h)*BrakeHorsePower;
-  PowerAvailable = Throttle*EngineMaxPower*HPTOFTLBSSEC - PowerRequired;
-  
-  return PowerAvailable;
+    // FIXME: this needs to be generalized
+    Percentage_Power = (6e-9 * ManXRPM * ManXRPM) + (8e-4 * ManXRPM) - 1.0;
+    Percentage_Power += ((T_amb_sea_lev_degF - T_amb_degF) * 7 /120);
+
+    double Percentage_of_best_power_mixture_power =
+      Power_Mixture_Correlation->GetValue(14.7 / equivalence_ratio);
+
+    Percentage_Power *= Percentage_of_best_power_mixture_power / 100.0;
+
+    if (Percentage_Power < 0.0) Percentage_Power = 0.0;
+    else if (Percentage_Power > 100.0) Percentage_Power = 100.0;
+    
+    HP = Percentage_Power * MaxHP / 100.0;
+
+  } else {
+
+    // Power output when the engine is not running
+    if (Cranking) {
+      if (RPM < 10) {
+        HP = 3.0;   // This is a hack to prevent overshooting the idle rpm in
+                    // the first time step. It may possibly need to be changed
+                    // if the prop model is changed.
+      } else if (RPM < 480) {
+        HP = 3.0 + ((480 - RPM) / 10.0);  
+        // This is a guess - would be nice to find a proper starter moter torque curve
+      } else {
+        HP = 3.0;
+      }
+    } else {
+      // Quick hack until we port the FMEP stuff
+      if (RPM > 0.0)
+        HP = -1.5;
+      else
+        HP = 0.0;
+    }
+  }
+}
+
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+/**
+ * Calculate the exhaust gas temperature.
+ *
+ * Inputs: equivalence_ratio, m_dot_fuel, calorific_value_fuel, 
+ *   Cp_air, m_dot_air, Cp_fuel, m_dot_fuel, T_amb, Percentage_Power
+ *
+ * Outputs: combustion_efficiency, ExhaustGasTemp_degK
+ */
+
+void FGPiston::doEGT(void)
+{
+  double delta_T_exhaust;
+  double enthalpy_exhaust;
+  double heat_capacity_exhaust;
+  double dEGTdt;
+
+  if ((Running) && (m_dot_air > 0.0)) {  // do the energy balance
+    combustion_efficiency = Lookup_Combustion_Efficiency->GetValue(equivalence_ratio);
+    enthalpy_exhaust = m_dot_fuel * calorific_value_fuel * 
+                              combustion_efficiency * 0.33;
+    heat_capacity_exhaust = (Cp_air * m_dot_air) + (Cp_fuel * m_dot_fuel);
+    delta_T_exhaust = enthalpy_exhaust / heat_capacity_exhaust;
+    ExhaustGasTemp_degK = T_amb + delta_T_exhaust;
+    ExhaustGasTemp_degK *= 0.444 + ((0.544 - 0.444) * Percentage_Power / 100.0);
+  } else {  // Drop towards ambient - guess an appropriate time constant for now
+    dEGTdt = (298.0 - ExhaustGasTemp_degK) / 100.0;
+    delta_T_exhaust = dEGTdt * dt;
+    ExhaustGasTemp_degK += delta_T_exhaust;
+  }
+}
+
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+/**
+ * Calculate the cylinder head temperature.
+ *
+ * Inputs: T_amb, IAS, rho_air, m_dot_fuel, calorific_value_fuel,
+ *   combustion_efficiency, RPM
+ *
+ * Outputs: CylinderHeadTemp_degK
+ */
+
+void FGPiston::doCHT(void)
+{
+  double h1 = -95.0;
+  double h2 = -3.95;
+  double h3 = -0.05;
+
+  double arbitary_area = 1.0;
+  double CpCylinderHead = 800.0;
+  double MassCylinderHead = 8.0;
+
+  double temperature_difference = CylinderHeadTemp_degK - T_amb;
+  double v_apparent = IAS * 0.5144444;
+  double v_dot_cooling_air = arbitary_area * v_apparent;
+  double m_dot_cooling_air = v_dot_cooling_air * rho_air;
+  double dqdt_from_combustion = 
+    m_dot_fuel * calorific_value_fuel * combustion_efficiency * 0.33;
+  double dqdt_forced = (h2 * m_dot_cooling_air * temperature_difference) + 
+    (h3 * RPM * temperature_difference);
+  double dqdt_free = h1 * temperature_difference;
+  double dqdt_cylinder_head = dqdt_from_combustion + dqdt_forced + dqdt_free;
+    
+  double HeatCapacityCylinderHead = CpCylinderHead * MassCylinderHead;
+    
+  CylinderHeadTemp_degK +=
+    (dqdt_cylinder_head / HeatCapacityCylinderHead) * dt;
 }
 
 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+/**
+ * Calculate the oil temperature.
+ *
+ * Inputs: Percentage_Power, running flag.
+ *
+ * Outputs: OilTemp_degK
+ */
+
+void FGPiston::doOilTemperature(void)
+{
+  double idle_percentage_power = 2.3;        // approximately
+  double target_oil_temp;        // Steady state oil temp at the current engine conditions
+  double time_constant;          // The time constant for the differential equation
+
+  if (Running) {
+    target_oil_temp = 363;
+    time_constant = 500;        // Time constant for engine-on idling.
+    if (Percentage_Power > idle_percentage_power) {
+      time_constant /= ((Percentage_Power / idle_percentage_power) / 10.0); // adjust for power 
+    }
+  } else {
+    target_oil_temp = 298;
+    time_constant = 1000;  // Time constant for engine-off; reflects the fact
+                           // that oil is no longer getting circulated
+  }
+
+  double dOilTempdt = (target_oil_temp - OilTemp_degK) / time_constant;
+
+  OilTemp_degK += (dOilTempdt * dt);
+}
+
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+/**
+ * Calculate the oil pressure.
+ *
+ * Inputs: RPM
+ *
+ * Outputs: OilPressure_psi
+ */
+
+void FGPiston::doOilPressure(void)
+{
+  double Oil_Press_Relief_Valve = 60; // FIXME: may vary by engine
+  double Oil_Press_RPM_Max = 1800;    // FIXME: may vary by engine
+  double Design_Oil_Temp = 358;              // degK; FIXME: may vary by engine
+  double Oil_Viscosity_Index = 0.25;
+
+  OilPressure_psi = (Oil_Press_Relief_Valve / Oil_Press_RPM_Max) * RPM;
+
+  if (OilPressure_psi >= Oil_Press_Relief_Valve) {
+    OilPressure_psi = Oil_Press_Relief_Valve;
+  }
+
+  OilPressure_psi += (Design_Oil_Temp - OilTemp_degK) * Oil_Viscosity_Index;
+}
+
+//%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+//
+//    The bitmasked value choices are as follows:
+//    unset: In this case (the default) JSBSim would only print
+//       out the normally expected messages, essentially echoing
+//       the config files as they are read. If the environment
+//       variable is not set, debug_lvl is set to 1 internally
+//    0: This requests JSBSim not to output any messages
+//       whatsoever.
+//    1: This value explicity requests the normal JSBSim
+//       startup messages
+//    2: This value asks for a message to be printed out when
+//       a class is instantiated
+//    4: When this value is set, a message is displayed when a
+//       FGModel object executes its Run() method
+//    8: When this value is set, various runtime state variables
+//       are printed out periodically
+//    16: When set various parameters are sanity checked and
+//       a message is printed out when they go out of bounds
+
+void FGPiston::Debug(int from)
+{
+  if (debug_lvl <= 0) return;
+
+  if (debug_lvl & 1) { // Standard console startup message output
+    if (from == 0) { // Constructor
+
+      cout << "\n    Engine Name: "         << Name << endl;
+      cout << "      MinManifoldPressure: " << MinManifoldPressure_inHg << endl;
+      cout << "      MaxManifoldPressure: " << MaxManifoldPressure_inHg << endl;
+      cout << "      Displacement: "        << Displacement             << endl;
+      cout << "      MaxHP: "               << MaxHP                    << endl;
+      cout << "      Cycles: "              << Cycles                   << endl;
+      cout << "      IdleRPM: "             << IdleRPM                  << endl;
+      cout << "      MaxThrottle: "         << MaxThrottle              << endl;
+      cout << "      MinThrottle: "         << MinThrottle              << endl;
+
+      cout << endl;
+      cout << "      Combustion Efficiency table:" << endl;
+      Lookup_Combustion_Efficiency->Print();
+      cout << endl;
+
+      cout << endl;
+      cout << "      Power Mixture Correlation table:" << endl;
+      Power_Mixture_Correlation->Print();
+      cout << endl;
+
+    }
+  }
+  if (debug_lvl & 2 ) { // Instantiation/Destruction notification
+    if (from == 0) cout << "Instantiated: FGPiston" << endl;
+    if (from == 1) cout << "Destroyed:    FGPiston" << endl;
+  }
+  if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
+  }
+  if (debug_lvl & 8 ) { // Runtime state variables
+  }
+  if (debug_lvl & 16) { // Sanity checking
+  }
+  if (debug_lvl & 64) {
+    if (from == 0) { // Constructor
+      cout << IdSrc << endl;
+      cout << IdHdr << endl;
+    }
+  }
+}
 
-void FGPiston::Debug(void)
+double
+FGPiston::CalcFuelNeed(void)
 {
-    //TODO: Add your source code here
+  return FuelFlow_gph / 3600 * 6 * State->Getdt() * Propulsion->GetRate();
 }
 
+} // namespace JSBSim