Scale speed (DCC Speed matching)

Why scale speed?

Operating my layout in a realistic way is important to me. The speed of the trains is one important aspect. By default many locomotives run too fast. To avoid running trains too fast and also to allow them to be running together in a consist I wanted to adjust the max speed that my locomotives can run. I decided to set the max speed to be 100 scale km/h. Most of the Norwegian locomotives, like the Di3, El11 and El13 had a maximum speed that is close to this. And 100 scale km/h is still pretty fast.

Speed curves

DCC decoders provide two ways to adjust the speed curve and therefore its speed over the complete throttle range. The basic adjustments are using a three point system. CV2 allows for starting speed adjustments, CV5 for the top speed and CV6 for a mid point adjustment. A more comprehensive way is the speed curve, where there are 28 CV's (67-94) that allow fine tuning the speed adjustments for speed step.

For most of the adjustments that I've done the basic adjustments were sufficient.

The default speed curve for both Zimo and ESU is not linear. I've changed that to be more linear.

Speed curve

Speed matching

I setup a basic oval with an Accutrack II Speedometer. Then I measured the speed at various throttle positions. The graph show three examples of locomotives before and after adjustments.

Speed curve

As seen in the graph all the three locomotives ran must faster than the 100 scale km/h. The Heljan Di3.633 ran 170 km/h at speed step 28. All three topped out at their max speed at an early speed speed. Therefore the complete throttle range is not used, which is something I don't like.

With the CV changes as seen in the table, all three locomotives were adjusted to the linear speed curve, and now all have a max scale speed of 100 km.h.

Model CV2 CV5 CV6
ESU default 3 255 88
Heljan Di3.633 1 90 45
NMJ Di3.615 1 150 75
NMJ El13.2134 1 165 82

Enter the new Loksound 5 family

I tried to stay with one decoder family and that was the ESU v4 series (Lokpilot v4, Loksound v4 & Loksound Select). Some locomotives came with Zimo decoders (Hobbytrade El13, NMJ Superline El14). Now ESU has completely revamped its decoder family with the new 5 series. At the time of writing (July 2020) I haven't had the non sound version but I got both the Loksound 5 and the Loksound 5 DCC decoders. The Loksound 5 DCC decoder is made specifically for the North America & Australian markets, it only supports DCC. The Loksound 5 is like the old MM version, it supports multiple systems and is mainly targetting the European market. NMJ Di3 locomotives with sound come with this version of the decoder and therefore I had to get them aligned with the 5 DCC and older v4 version decoders.
Model Decoder CV2 CV3 CV4 CV5 CV6
NMJ Di3.620 Loksound v4.0 3 125 255 120 60
NMJ Di3.621 Loksound 5 3 125 255 145 not supported
Heljan Di3.641 Loksound 5 DCC 1 35 255 245 123
NMJ Di3.630 Loksound 5 1 35 255 255 128
The differences between the Loksound 5 and Loksound 5 DCC are very apparent in this comparison.
  • The Loksound v4 and Loksound 5 all use a momentum multipler of 0.25
  • The Loksound 5 DCC uses the NMRA Standard momentum multipler of 0.896.
  • The Loksound 5 doesn't support the 3 point speed table (hence no CV6)
The momentum multiplier difference is visible if you compare CV3 in the table as they are all set to a similar behavior value.

Resources

Last update: 2020-07-26