First off let me start by saying I’m sorry if this is a duplicate thread to something that has been posted recently, but I have been in and out of the forums for a while so I may have missed something.
Anyway, my question is, as the title implies, how to go about getting two locomotives to match in speed. I’ve got several Athearn SD40-2s and a Walthers GP15 (both are newer, RTR locomotives, but they did not come DCC ready), and I’ve got NCE D13SJR decoders in them. Right now they don’t match in speeds, any sometimes one will tends to push or pull the another one. I know this can be fixed somehow using CV’s so that they match fairly closely anyway. Problem is that I don’t know which ones or how to go about adjusting them, and I’m hoping someone knowledgeable on the subject will take the time to explain it to me. I’ve looked over my Decoder manuals, but I don’t see any detailed, how-to information in there on this subject anyway. I use a Digitax Zephyr on my layout and for programming, although I do have access to a Digitax Empire Builder if that would make it easier to do the programing.
In your situation you might find it easiest to use the “golden loco” method - that is, pick one engine then change the CV’s in the other engines until they match the “golden” one. I start by matching the speed. I start with the top speed (CV5). (In default, your decoder will have -0- for all these CV’s by the way.) The top speed is 255. If the loco is going faster than your golden one, bring the top CV down by say 25 to 230 and see how that works. Sometimes that is enough right there. Otherwise, after that you may need to do both CV5 (top speed) and CV6 (midrange). In general, CV6 should be halfway between 0 and the top speed - so if your topspeed CV5 = 150, CV6 = 75. There’s no great shortcut, you just have to change the CV’s by trial and error until you get the two engines running together. (CV2 is your start speed. I often get by without adjusting this one, but if one engine starts quicker than the other, you can put the slower one’s CV2 up to 10 or 20 and then add 10 or so each testrun until it starts the same time as the other.)
Then I go to CV 3 and CV4, start and stop momentum. I like to set these to about 12-15 on the first engine, then adjust the other engine’s CV 3 & 4 until they start together and coast to a stop together.