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A Guide to Driving with the AI Fireman OFF

By Will Cook (aka nigelgresley), Copyright ©2002 - 31 May 2002

This is a rough guide to firing and driving steam locomotives in MSTS. This is not meant as a guide for the operation of real steam locos as there are shortcomings to MSTS ones!

In MSTS the locos behave slightly differently to the real thing. However, it is possible to apply some of the techniques that real enginemen use. Before I can explain exactly how and what to do, I feel it is important to understand what some of the controls do:

Live Steam Injector
Injectors are used to force water into the boiler, the injector uses steam to create a vacuum to drag water through the injector cones and into the boiler, the live steam injector uses live steam direct from the boiler for this purpose.

Exhaust Steam Injector
The exhaust steam injector does exactly the same as the live steam injector, but it uses steam exhausted from the cylinders to put water into the boiler, and therefore it is much more economical. However, it can only really be used when the regulator is open, as that is the only time that steam is exhausted from the cylinders.

The reason I have covered the use of the injectors first is because it is arguable that they are the most important controls in the cab, as if the loco runs short of water, the firebox crown (top) will melt and implode, and it is a moot point whether the boiler would explode too.

Most people know what this does, however, most locomotives use what is called a twin port regulator which means that there are actually two regulator valves controlled by the regulator. The small valve (known as first valve) will only give you a limited amount of steam to the cylinders, so therefore it can be used for starting the loco, and for running when you want to keep an even speed. In MSTS, the first valve is from 1%-49% on the regulator. The second valve is much bigger and is from 50%-100% on the regulator in MSTS. The second valve will give you much more steam pressure in the cylinders, and therefore more power so it can be used when you want to accelerate or anything else where you want a lot of power.

This is sometimes known as the cut-off, and it can be likened to gears in a car. The reverser should realy be somewhere near 75% when first starting the loco, then you can wind it back as your speed increases (just like changing up the gears in a car), winding it back makes the loco more economical on coal and water.

Steam Chest
The steam chest pressure gauge tells us about the pressure of the steam in the cylinders, and so therefore it also tells us about the power of the loco at that point in time, as the pressure pressing on the piston head in the cylinder drives the loco down the track.

The blower when turned on puts an extra draw on the fire, therefore drawing air through it and heating it up. This does not need to be on all the time, as when the loco is underway, the exhasted steam from the cylinders will provide sufficient draw on the fire.

The dampers are doors below the fire that when open allow the fire to breath and therefore giving it the air it needs to good combustion, and therefore heating it up.

Please ensure that to avoid the blowback of the fire into the cab you must have the door shut and the blower on 100% when going through tunnels, this is one of the bugs with MSTS, as that does not apply to real steam locos.

You can tell if the loco is priming by looking to the bottom on the HUD. Priming is when water is carried over through the regulator valve and into the cylinders, on the real thing this can cause the cylinder to explode, and and bent con rods, this can be averted by opening the cylinder cocks to drain the water out of the cylinder.

Fire Level
The fireman's job is to supply steam to the driver, if the fireman doesn't supply enough steam (like if you are going up a bank flat out), then the boiler pressure will begin to drop and drop, and before you know it you are right up the creak without a paddle! For firing with the AI fireman off it is advisable to have the HUD (Heads Up Display) on, you can do this by pressing F5 twice. Once the HUD is up you will se all sorts of interesting values, the main ones that you should look at are Firemass, Steam Generation rate, Steam Useage rate, Boiler pressure, Water level.

Firing a steam locomotive has been described as being a balancing act, and it is. It is a balancing act because you have to balance the amount of fire against the water level against the boiler pressure. A good rule of thumb for the fire level is to look in the .eng file at the 'ideal fire mass' and to try and keep the fire mass at that level in the duration of the sim. What I personally do is to let the fire drop 50lbs below the ideal firemass, and then fire again to bring it up to the ideal firemass, this way you will always have the correct amount of fire.

Firehole Door
Obviously having the door closed keeps the heat in better, and so the fire temperature is likely to rise more quickly. However, with MSTS locos the steam generation rate drops when you shut the door, so , as part of the balancing act mentioned above I would personally shut, or partially shut the door if I can, however, if I'm struggling for steam then within the contexts of MSTS it seems to be best to open it.

Boiler Management
The balancing act I mentioned above is more commenly known by enginemen as boiler management, here are two good rules for boiler management:

  • If you have too much steam, do something to get rid of some of it.
  • If you don't have enough steam, do something to bring down the steam useage rate.
Here's how these rules can be applied:

Too much steam:

  1. Put an injector on, this will raise the water level, and use up some steam.
  2. Open the regulator a bit more, this will use up more steam
  3. Make sure the small ejector is open
  4. Make sure the brake is 100% released

Not enough steam:

  1. Close the small ejector as this uses steam
  2. Move the brake into the running position as this will save steam
  3. If you have steam heat on, turn it off, I'm sure (some of the time) that you passengers won't mind getting to their destination cold rather than extremely late!
  4. Turn off injectors if you have them on (unless the water level is dangerously low)
  5. Close the regulator a bit, this could save you some steam, unless you are struggling for speed.
  6. Move the reverser back a bit more, this will also save some steam, unless you are struggling for speed.

Not all of the above need to be implemented in each case, as not all of them will suit the situation in which you find yourself.

The economical working of a loco can mean the difference between getting to your destination or not at all. One good way of being economical, is to work with minimum regulator and reverser settings whilst still keeping to schedule. If you go everywhere working flat out you will use too much coal and water, and go too fast as well. The best way to find out what the minimum settings should be is by experiment, looking at the current speed at the projected speed and seeing what affect you changes in regulator and reverser setting have on them.

In connection with what I have said above about the regulator, you will see that there is a difference in steam useage between 49% and 51% this is the affects of putting the loco into second valve, so therefore it is more economical to have the regulator at 51% than 49%, but conversely, if you have got too much steam and want to get rid of some, then 49% might be a good thing.

I hope that this will provide you with a good insight into how to driver/fire a steam locomotive in MSTS. Some parts may be complex, but if you can grasp at least some of the ideas, then you will get on much better with steam locos, also a lot of this comes with practise, and I am a real steam fireman, so therfore I know about the workings of steam locos, and some of my knowledge can be applied to locos in MSTS, however the MSTS locos do no behave quite like the real thing! Whatever you are firing, be it a real steam loco or an MSTS one the only way to improve as any kind of engineman is by experiance, people can only teach you a certain amount, but you will learn most from getting your hands on the job, and learning from your mistakes, as something like this can only give you a grounding in the ideas behind steam locomotive operation, but what I have had to say is still worth listening to as it can make the difference between a good engineman and a brilliant one.

Compiled by

Will Cook 2002 (

Scottish Central PLUS




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