CV values for Smoke Volume in MTH Steam Locomotives is a free Model Railroad Discussion Forum and photo gallery. We cover all scales and sizes of model railroads. Whether you're a master model railroader or just getting started, you'll find something of interest here.


New Member
I want to change the smoke volume in a MTH Challenger Steam locomotive.
I already know that you can modify the smoke volume toggling Function 18, and that It can be varied in three levels: low, medium and high.
However It is not enough for me. I consider that the Locomotive should throw more smoke, I would like that!
I am completly sure that there is a CV, or two or three of them, that can be modified to achieve the effect I want, but I have not been able to get this información anywhere.
Wich are the CV variables that control the smoke in a MTH Steam Locomotive?
Wich are the min, max, and default values for each of them?

For example, suppose the default value, for the CV I am looking for, could be 60, and the max value 100 (just for the purpouse of this example):
then maybe the low level (triggered by Function 18) would be 20, the medium level 40 and the high 60.
If the value of this unknwown CV (at least for me) could be changed to 90, then the corresponding levels of the smoke volume would be: low 30, medium 60 and high 90 Wich would be under the supposed max value and would represent an increment of 50% in the smoke volume...

Can somebody help me??


Master Mechanic
DCC compatibility is not a priority for mth. In fact they would prefer that there wasn't any DCC at all. They have restricted the CV's that can be changed. I would suspect that if you could use on CV 18 the normal range to change the smoke volume, that the range would be between 0, meaning no smoke, to 255 meaning largest amount of smoke released.Whether or not mth will let you use anything other than a low, med or top setting, is anyone's guess.

Here is a link to the mth challenger webpage. It gives you a list of CV's but not what the ranges are.


New Member
Thank you for your reply. I agree with you that the common values of CV's are in the range 0-255. However in the case of the CV that controls the temperature of the smoke system in a Broadway Limited Steam Locomotive the range varies from 0 to 100.

Other detail is that the number of the CV asociated with the Function that controls the smoke volume (that is F18) would unprobably be 18, it has another number.

One thing is the number of the Function and another one is the number of the CV asociated to certain effect controled by the decoder like sounds, lights or smoke. They are diferent. That is what I have learned by studying the technical manuals of Broadway Limited Paragon 2 and Athearn Tsunami decoders.

There is a lot of information for programming the decoders of these brands but I have not been able to get It for the MTH PROTOSOUND 3 System. I know MTH is not very interested in DCC compatibility but all these is electronics, all the decoders are alike, so a table of CV's exists for the MTH decoders

Thank you, but it seems that we will have to continue looking for the answer...
Last edited by a moderator:


Master Mechanic
I wasn't aware that there were other ranges available besides 0-255. That just seems like a "universal" range of settings, and not just in decoders. I have never seen a list of CV's that mth has for any locomotive. Their concept of DCC compatibility shows in their stubbornness in not giving you a list of numbers that can be used to adjust some of the CV's they say are compatible. Its like when they released their first version of their "DCC ready", SD-70ACEs. They didn't bother to tell you that their light boards in the models had IIRC a positive ground, whereas every DCC decoder has a negative ground. This little omission led to a lot of blown decoders. I still don't know if they ever changed it.

Its things like this that contribute to my distrust of anything from mth.


New Member
I have posted this same question in the Contact Service menu, in the MTH web site, I hope they give an answer.
If anyone has information about this I would appreciate that you share it...

Affiliate Disclosure: We may receive a commision from some of the links and ads shown on this website (Learn More Here) is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to - An online railroad bookstore featuring a curated selection of new and used railroad books. Railroad pictorials, railroad history, steam locomotives, passenger trains, modern railroading. Hundreds of titles available, most at discount prices! We also have a video and children's book section. - An online model railroad bookstore featuring a curated selection of new and used books. Layout design, track plans, scenery and structure building, wiring, DCC, Tinplate, Toy Trains, Price Guides and more.