This review will be for the Union Pacific Challenger and Big Boy DLC. First of all, these two DLC offerings are perhaps the worst quality DLC ever offered for this game. There is a littany of problems with both of these DLC packages which are the same for both engines. I will only touch on a few of the many issues.
1) While these engines look like the prototypes in the academic sense, they lack many fine details. There are many pipes, rivets, auxilliary devices, and linkages that are missing. If these were real locomotives they would not be operable for the want of so many important parts. A five year old might not notice, but an adult with any knowledge of railroad history in general and steam locomotives in particular will immediately notice the missing details. The cab interiors are just as bad. There are several missing pipes, levers, and gauges that are missing. The cab windows do not open. There are no cab lights so it is pitch dark inside; all the better to hide the missing details. Also, there is no engineer or fireman.
2) Missing or broken features are many and are overwhelmingly immersion-breaking. There are some things that a steam locomotive has to have in order to be immersive; it must transport you to that special place where you believe that you are actually running a steam locomotive. Well....., these engines lack all of those things. First of all, the headlights and tender lights do not work. Secondly, the sounds are bad. The chuffing of the engines sound like someone using a plunger on a toilet; a kind of wheezing, squishy sound. What makes this even worse is that the sounds were borrowed from the Somerset and Dorset 7F 2-8-0 British freight engine. While I feel bad for fans of the 7F who might lament its poor sounding exhuast, the problem with using this sound for the Big Boy and Challenger is that the 7F is a two cylindered locomotive, while the Big Boy and Challengers are 4 Cylindered simple articulated locomotives. Even if the 7F didn't sound like a dying water buffalo, a two cylindered engine chuffs 4 times per revolution of the driving wheels. By contrast, a simple articulated would have two different sets of cylinders each chuffing 4 times per revolution; they would get out of sync with one another causing a stacatto rythm, 8 chuffs total per revolution, called "hitting a double lick". This sounds NOTHING AT ALL like a 2 cylindered locomotive. Ditto for the whistle sounds, hissing steam, and the "clunking" of auxilliary devices, all of which are missing, bad quality or poorly synced. What RSC should have done was to get sound samples from the real Union Pacific Challenger #3985, using the samples for both the Challenger and the Big Boy. It would have worked beautifully, but I guess that would have been too easy to do.
My biggest deal-breaker when it comes to immersion with a steam locomotive is the lack of a fully functioning set of particle emitters to model the various steam and smoke exhuasts on the locomotives in question. After all, if a steam locomotive isn't steaming and smoking, it isn't much of a steam locomotive is it? The smokestack exhuast looks far too thick and doesn't dissapate the way real smoke does. Essentially it looks like a column of dirty cotton candy shooting up and out, fluffy and irregular. The emitters for the cylinder ♥♥♥♥♥ do not work. The emitters for the wheel sanders do not work. The emitters for the boiler safety vavles and turbo generators do not work, but that is okay, I suppose, becuase RSC deigned not to add models for the pop valves and turbo generators anyway. The emitters for the inectors and feedwater pump are not present/do not work. And on the Big Boy, there is no stoker motor exhuast.
3) The performance of these locomotives is completely unrealistic. First off, the models possess far too much tractive effort, that is, low speed pulling power. While the Real Challengers and Big Boys were indeed powerful locomotives that could start and rapidly accelerate heavy trains, they didn't accelerate to 80 mph in ten seconds.TOTALLY UNREALISTIC. On the other end of the spectrum, the horspower curve is too weak. The real locomotives could sustain 40-60 mph speeds with heavy trains, effortlessly for hundreds of miles. These DLC engines,"run out of boiler" within a few seconds of high speed running and can't run at all with any significant load behind them. They run out of steam and stall, forcing you to stop and build up steam again. COMPLETELY UNREALISTIC.
Both the Challenger and Big Boy DLC were obvious "rush-jobs" cranked out without any thought to accuracy, realism, or quality control. These could possibly be the worst DLC offered for this game. The content creator who made the DLC and the people who made the release decision either don't like their jobs, or don't care about North American railroad history, both of which are bad news for a company that makes a "Train Simulator". The decision to sell this DLC does a disservice to Dovetail Games, its other content creators who will be "tarred by the same brush", the Train Simulator franchise, and two legendary locomotives that deserve better representation than this. My only hope is that Dovetail Games will rectify their mistake and build brand new models of both of these locomotives to the level of quality of the Smokebox F.E.F. Normally, if a DLC release is average in qualtiy I will recommend a "buy" decision, with the qualifier that the purchaser wait for a sale. With this release however, I cannot countenance a purchase decision. The Challenger and Big Boy DLC are awful, don't buy them, period. And this is coming from someone who loves North American steam locomotives and the Train Simulator game.
Final Rating: Steaming pile out of 10 stars. Avoid like the plague.