The mechanism. After removing the couplers I could easily lift off the plastic body shell. A die-cast metal weight runs along the length of the chassis and over the top of the dual-flywheel-equipped can motor. The motherboard and lighting boards are mounted atop the weight. All lighting is provided by surface-mounted light-emitting diodes (LEDs).
On our DCC-equipped sample, the ESU LokSound Select decoder is plugged into a 21-pin socket on the motherboard. Behind that is an enclosure with an oval speaker that faces up.
Performance. As shown in the charts at right, the Bowser SD40-2 features smooth performance in direct current (DC) and Digital Command Control (DCC). On both our DC and DCC test tracks, the model accelerated from less than 1 scale mph to 55 scale mph. This is 10 mph slower than the top speed of the lowest gear ratio available on the prototype, but it’s more than fast enough for freight operations on a model railroad.
The model easily rounds 18"-radius curves and has plenty of pulling power on straight and level track, as noted in the charts. I also used the locomotive to pull a 10-car freight up a 3 percent grade. The model’s back electromotive-force (BEMF) control kept the speed constant both up and down the hill.
For DCC users, the decoder supports setting up a simple three-point speed curve with CVs 2, 5, and 6, as well as full 28-step custom speed curves. The decoder is programmed with some momentum effects right out of the box, but both acceleration and deceleration rates are easily adjusted with CVs 3 and 4.
A paper quick-start guide is included. A more extensive manual is available as a free download at www.esu.eu/en/start/.
Sound. After setting the SD40-2 on our DCC-equipped layout, I pressed 8 and heard the 645 engine start. The sound is clear without any buzzes or rattles. Notching occurs automatically with the throttle. I appreciated that the decoder’s functions include the ability to manually notch, so that I could increase and decrease the rpm sound independently from the locomotive speed.
The default bell and playable air horn sounded prototypical. For those that disagree, other options include an E-bell as well as 15 other air horn sound samples.
Function 4 triggers a realistic dynamic brake sound sequence. I heard the engine go down to an idle, then notch up before the fan sound started. Pressing the button again causes the fan sounds to gradually stop, then the engine drops down to idle and notches back up.
Other user-triggered sounds include sanding valves, compressor, and spitter valves. The volume level of each effect is adjustable and functions can be remapped to any available throttle key. Many of these programming tasks, including function mapping, require setting an index CV before programming the CV that performs the specific task.
The model features a realistic lighting package with ditch lights and dimmable headlights. Our CP Rail prototype also has a lighting feature I’ve never seen before: adjustable class lights. With the push of a button (F5) I toggled the lights between white, green, red, and off.
DC operation. Most of the sound and light effects are more limited when the locomotive is operated on a DC layout. The white class lights remain on and the headlights operate according to locomotive direction.
That said, I find that ESU LokSound decoders offer some of the best DC performance compared to other dual-mode decoders. The engine rpm sound realistically notches up before the locomotive starts moving. There’s no interruption in the sound when I flip the direction button on the power pack. As long as I kept the track voltage above 6 volts (or with the throttle dial of our MRC Tech4 set to the 12 o’clock position) the SD40-2’s sound and lights didn’t cut out. To access sound effects other than the diesel engine, an analog sound controller, such as an MRC Tech 6, is required.
The impressive ESU decoder means that the model’s performance matches its good looks. Accurately modeling its Canadian prototype, the Bowser GMDD SD40-2 looks like the successful result of a superdetailing project, except that I didn’t have to do anything but open up the box.