How do you fine tune a loco on DCC (CV Adjustments)?


KB02

KB02

Well-Known Member
What methods work for you?

I have been fiddling with my locos now that my layout and locos are getting converted over to DCC. I have gotten most of them to run better, but I have hugely different settings for each Loco. My Bachmann GP 40 creeps along nice & slowly at speed step 1, but I have a starting voltage of 25. My Rivarossi Hudson creeps along in Speed step 1 at a starting voltage of 5. At a top voltage of 255 my GP40 scoots out pretty good, but my Athearn GP38-2 hits warp speed with a top voltage of 175.

???

Obviously, it will be different for every loco, but what CV adjustments do YOU do, AND in what order?

I have found this all very confusing.

Thank, all!
 
I use JMRI Decoder Pro to tune my speed steps.

I do not use starting voltage or CV3, 4 or 5 I think they are.
I set the lowest speed step to where the engine just moves and is running smoothly.

I then set the last or step 28 to the top speed I want the engine to run.
Select match ends and write to the decoder.

Fiddle with speed steps 2 through 27 to get the mid running operation you like.
On switchers sometimes the constant curve selection works well.

EDIT: Also in JMRI, be sure to select the button at the top of the speed step page to use speed steps.
 
There are some very informative videos on MR Video Plus by Dana Kawala that explain a lot of basic to intermediate DCC features. Well worth the subscription.
 
What surprises me is that brand new locos just coming out still don't have realistic speed ranges. I have some Kato SD40's that have top speed set at something like 70. When I've powered them up to full factory-capable speed I actually start to wonder if they're going to tip over on the curves. Why on earth are manufacturers still turning out rocketship locos instead of ones that run at realistic speeds? Ah well. On the flipside I have Fox Valley locos that actually don't run quite as fast as they should, at least in my opinion, but since those are the slow boats of my roster everything else has been relegated to their top speed, which may be more realistic than I realize. Hard to just judge what a real-life counterpart to their speed would be using just your own eyes and perception.

I don't use JMRI (yet), so my methods probably won't help you. Having said that, it's really not hard at all to speed match locos using programming via main once you get a little practice at it. I run the unmodified decoder behind the unit which I use as a base for speed measurement. Find out what throttle setting comes close to matching the speed and use that as a percentage of 255 to guesstimate the top and mid speeds. Program those in and let 'em go, then fine tune it as they run around. Once that's figured I add in the acceleration/deceleration momentum, again based on what top speed I set and prior experience. Fiddle with that until they match and you're done. Of course there's also the EMF settings and so forth to set if you like, and they are extremely useful in fine-tuning a loco, but that's a whole other can of worms.

The bottom line is that even with the same exact model of loco, you can have some significant variation in their settings. Speed-matching locos isn't a matter of what exact numbers fit which model because they all do run just a tiny bit differently. I'm also starting to see that as some of my locos are now getting significant operating time and the drive trains have settled in, loosened up, whatever you want to call it, they need a little fine tuning. I've always "broken in" my locomotives when I get them, but apparently there's a bit of difference between an hour around the layout and 20 hours around the layout.
 
Well, I don't even have a computer that I could run JMRI with, so the handheld controller/programmer is the method that I am using - Manually adjusting CV's as I go.

As an example:
I converted my switcher over to DCC last night and put it to the track for programing/testing. On 28 speed steps, I finally got it to move on Speed step 7. Then it was going at a pretty high speed. I adjusted CV116 to 1 and CV117 to 25 and lowered the Starting voltage to 5. It started off in speed 1 no problem, but still a little fast (at least for speed step 1). I tried adjusting different settings back and forth, but those numbers gave me the best results. (I also adjusted top voltage down to 100 as the little bugger wanted to speed away like crazy at full throttle.)
Is there something else I should adjust? The other three engines I have will crawl along much slower than this one.
 
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