DCC Welcome Page‎ > ‎DCC Decoders‎ > ‎

Decoder Motor Tuning

Typically the factory settings normally provide good performance for most locomotives.   But given that decoders may encounter many different types of motors and gear ratios, the performance may vary and become less than satisfactory.   This section's goal is to help you get the most out of your locomotives motor performance.  We are talking about low speed performance and/or speed standardization.


Many advanced decoders have various motor speed tuning features such Speed Step modes, Speed Tables, Back EMF (BEMF), Torque Compensation, Kick Start, Start Voltage, Mid Voltage and Max Voltage.  Go here to see the features and definitions:
Motor Control Term Definitions


Here is some information on the various issues in doing speed matching:
Speed Matching Thoughts

If your decoders have a feature called BEMF, also read the next section below.  You will need to get the BEMF setup properly first before doing any speed matching.

Speed matching involves the use of the decoder 28 speed step table to give you the level of find speed control you will need.  A Decoders CV's called Vstart, Vmid and Vmax (see Feature Defintions above for more information) form a course 3 speed step table.  This simple but crude speed table will not offer the precision you will need to get good speed matching over the entire range of speeds possible.  On the other hand, making 28 speed step adjustments can be a big task.   Fortunately to help you get both a EASY and FAST way to get a handle on so many adjustment, you need computer software such as JMRI Decoder Pro.  The speed table programming is part of the JMRI Decoder Pro software which can be found here:
JMRI DecoderPro

Jim Betz, a long time DCC guru, has a lot of experience with manual speed matching and general tuning locomotives.   He has written a document that combines all his knowledge and is available for you to download and read.  He uses JMRI Decoder Pro to manually make the adjustments. Click here for his downloadable presentation:
Jim Betz Decoder Tuning

Jim does favor large momentum values out of the desire to have prototypical response.  But unless you have a large layout to run on, it may not be your cup of tea so to speak.

The biggest problem with tuning to a absolute accurate speed is that you have a speedometer to measure your trains speed.  The following devices are available for speed tuning:

Multi-Scale Train Speedometer (MSTS)
Speedtrak Speedometer  (Toth Technologies)

If you want to use to popular JMRI free software and do speed matching at scale speeds, you need this system:
Bachrus Model Train Speedometer

The JMRI application window you need for Bachrus is found here:
JMRI Speedo Window app for Bachrus


Want to know what BEMF is, go here:

BEMF is feature found in advanced DCC decoders.  However, the implementation from DCC manufacture to DCC manufacture can vary a lot in term of both performance and CV tuning options.  Look below in the list of subpages and click on the DCC Decoder Manufactures your interested in to see the details of how each is done and tuned