Speed Matching

One of the good reasons for any modeler to go into DCC, even if they don't run with multiple operators, is the ability to speed match locomotives. In the old DC days, it really wasn't a good idea to run Athearn and Atlas locos together in MU. More recent higher-quality Bachmann and Walthers locos provide the same sort of problems. However, speed matching with DCC is fairly easy.

A lot of guys on YouTube, and MRVP as well, tend to make things harder than they need to be. Some say you need a scale speedometer to match speeds, and others say you need to fiddle with BEMF CVs. This may be necessary in some cases, but I've found that 90% of diesels can be speed matched simply with 3-point speed curves and adjustment of CV2, the starting voltage. The rules of thumb I've found:

• Use CV2 to be sure both locos start at the same speed step. You set up a DCC consist with your control station and put both locos on the track, but don't couple them. Start the consist and see if both locos start running at the same time. If one doesn't and the other does, increase CV2 by small increments in the one that doesn't until it starts at the same time as the other loco.
• Using the same technique of putting both locos in a consist but not coupling them, try running the consist at a faster speed and see if the locos match speeds. You don't need to be exact, just be sure one doesn't catch up to the other right away. If one is faster, adjust CV6, the mid-range voltage, down by increments of 10 or so until the two locos run at visually a close speed.
• Then try running them coupled, maybe doing some switching work or running a freight with them around the layout. Check especially to see if one isn't pushing the other hard or holding the other back. If this happens, keep adjusting CV6 on either loco until the problem is fixed.
• Listen for scraping or groaning sounds that might indicate a loco is being dragged or pushed. Adjust CV6 on the faster loco (generally) until this goes away.
• If one loco has a lot more flywheel dwell time than the other, you can adjust acceleration and deceleration momentum with CV3 and CV4. This keeps one loco from shoving the other just because its flywheel runs longer. Very small changes in the value will work wonders.
• No two locos are exactly alike. Two locos can run at the same speed at a mid-range speed step, but their acceleration and deceleration can vary from 0 to the middle speed step. If you have the big issues solved, this won't be a big problem.
• Make notes of what values you put in the CVs!

Here are some examples of multiple-maker locos that I've speed matched.

The first, below, is a new Walthers SD70ACe that I speed matched with a Bachmann SD40-2. The Bachmann SD40-2 is a special case, because it doesn't have flywheels. But when I set CV3 and CV4 to 1 on any non-flywheel Bachmann loco (like older GP40s), it runs just like a flywheel loco. These two locos match speeds very well.

A Bachmann GP40, an Atlas Classic silver GP7, and an Atlas U23B:

A yellowbox Atlas C425 and a Walthers Proto GP30:

A Bachmann GP7 with an Atlas Classic silver GP7. Note that Bachmann DCC on board locos with factory decoders must have their factory decoders replaced (NCE BACH-DSL decoders are specifically meant to do this on many types) to enable speed matching, but when this is done, these locos operate and speed match very well.

An Atlas U23B and an Athearn GP38-2: