DH4 Diesel Road-Switcher

The DH4 Diesel Road-Switcher is a diesel-hydraulic engine with 4 powered axles. It is a middle-of-the-road engine that is more powerful than shunters like the DE2, while still retaining remote controller compatibility. It has a MU Cable, and is thus able to be used in multiple unit operations, but is not compatible with the DE6's slug. It was added as part of the Simulator update.

It has a massive fuel tank and the second highest fuel consumption of any diesel vehicle in the game, only beaten by the DE6. Although it has good power and is easy to operate, do not expect a cheap fuel bill.

## Operation

The DH4 uses a diesel engine connected to the drive train (wheels) through torque converters. There are three torque converters with different ratios, serving as "gears" for the engine. The switching between them occurs automatically, based on current speed and throttle level.

A characteristic of a torque converter is that the larger the difference between engine and drive train RPM (indicated by white and red needles on the tachometer, respectively) the more torque it generates. The higher the torque the more friction occurs in the transfer medium (oil) and the more heat is generated.

To help mitigate this, the DH4 is equipped with an active cooling system which will kick in when the oil temperature reaches 80°C and will continue working until it drops below 60°C. Its operation is indicated by the blue light on the oil temperature dial. This is in addition to the slow passive cooling down to the ambient air temperature (which in current version of the game is permanently set to 25°C).

Additionally, the engine comes with an active braking system which turns the torque converter into a fluid brake. Depending on the speed of the train this may generate a significant amount of oil friction and therefore heat. The throttle needs to be closed for it to be used.

## Gameplay

Despite the intimidating size and amount of noise the DH4 is very easy to operate. The fluid coupling makes it impossible to stall the engine, the gear shifts occur automatically, and the active cooling works equally well at any speed. Even overheating the oil is very uncommon as long as full throttle isn't applied.

Indeed, if the DH4 has a fault it is *too much* automation. At higher speeds, once you get into the third torque converter gear, acceleration becomes very difficult; getting past even 50 km/h can prove a slow endeavor at heavier weights. Sometimes, the locomotive can wait too long to downshift when beginning a climb, losing you valuable momentum.

Using the west-north Harbor route as a benchmark, the DH4 seems to be able to handle loads up to about 600t total (estimated based on pulling 534t that way + 80t for the engine) but you probably want to stick to around 500t total to avoid excessive RPM and therefore fuel use / engine damage.

As a road-switcher, the DH4 is effective at both medium-tonnage freight hauls and shunting; and since after a freight haul is finished a new job is created at that station to unload the delivered freight, the DH4 can effectively make two jobs out of one haul - hauling the freight to its destination, and then immediately unloading and storing it. Of course, this is possible with any locomotive, but the DH4's agility makes it peculiarly well-suited to the task.

## Trivia

The DH4 is based on DB Class V90 (here in English/German) being nearly identical in terms of looks & technical parameters.

The DB Class V90 is still in use to this day.

## Notes

* The DH4 is the least fuel-efficient locomotive in the game, with a load rating inferior to the DM3 but a fuel consumption comparable to the DE6.
* The DH4 has niche use as a heavy-duty, remote-control-capable shunter for assembling massive (1500+ ton) trains to be hauled by larger locomotives.
* Be careful when slowing down at high throttle; the downshift will create a sudden massive increase in torque, which can easily lead to wheelslip.
* Using 2 DH4 in an MU configuration results in a pulling capacity of 1600 tons, which is 200 tons more than the DE6 with 1400 tons and makes for a capable mid-game heavy haul setup. Operating cost will be double, so this is to be done with care on picking high paying jobs.

## Gallery

One of the first looks at the DH4 from the simulator teaser videos.A V90 on which the DH4 is based on.