Automatic merge of T1.6-186-g21d9ada29 and 13 pull requests

- Pull request #1082 at af5bc46: Allow variable water level in glass gauge
- Pull request #1057 at 85bde8e: Switchable brake system
- Pull request #1081 at a8127a1: Brake cuts power unification
- Pull request #1091 at 378be55: Automatic speed control
- Pull request #1122 at 73c47b4: Wagon Size and Centering Controls
- Pull request #1124 at e241a0d: Built-in PBL2 brake controller
- Pull request #1128 at b6c197f: Particle Emitter Overhaul
- Pull request #1158 at 2599bfe: Temporary fix for bug 2121985: F9 TCO out-of-range after resume
- Pull request #1169 at 906f204: Revise TrainCar.SetUpWheels to Better Handle Unusual Rolling Stock
- Pull request #1175 at d28315e: Make Data Logger interval configurable
- Pull request #1176 at 4cd961b: Remove Implicit Requirement for Engine Name to Come After "Engine ("
- Pull request #1178 at 015769e: Fix Diesel RPM Rate of Change
- Pull request #1183 at 41911f1: docs: Add code guidelines for translations

Author: openrails-bot

Source/Documentation/Manual/physics.rst

@@ -1613,6 +1613,35 @@ will be determined by a number of factors, and principal amongst them are the fo
 
 To display the changing water level in the Cab, use ``BOILER_WATER_GRADE``.
 
+Steam Water Injectors
+.....................
+
+Water injectors are typically modelled by default, and sizes and injection rates will be calculated automatically by OR.
+
+If desired the user may customise some of the default values by using the following parameters:
+
+``InjectorTypes ( x, y )`` - will allow the user to set up a combination of exhaust or live steam injectors for the 
+locomotive. Use 0 = Live steam and 1 = Exhaust steam in either of the x or y positions.
+
+``ORTSInjectorSize ( x, y )`` - the size of each injector can be indicated in this parameter. The values will be in 
+mm, and typically should not be greater then 19mm.
+
+
+Locomotive Back Pressure
+........................
+
+OR calculates a default back pressure value for the exhaust steam emitted from the cylinder.
+
+The user may customise the default value where appropriate values are known, ie from test reports, etc.
+
+To customise the backpressure curve use:
+
+``ORTSCylinderBackPressureVsSteamOutput ( x, y )`` - where x = series of cylinder steam usage rates in lb/h, and y = back 
+pressure in psig.
+
+Note: The older parameter ``ortscylinderbackpressure`` is inaccurate and no longer supported in OR. An error message will 
+display if OR detects the use of this parameter.
+
 
 Locomotive Types
 ................