Tsunami decoderIn the previous post I described the sound upgrade of the Virginian 737. Now I will tune the decoder so the loco will run as smooth as possible.

Remember, this is just a guide, you can (and should) always adjust the settings the way you like the most. It’s just an example of how it could be done.


CV settings Virginian 737

First I set the primary decoder address to 37
CV 1: 37,loc address
Then I set the start voltage to 0 volt
(I’ll explain later how you can get your loco to run very slow, see ‘run slow’ below)
CV 2: 0, start voltage
Next we put some momentum in the decoder, a locomotive this size takes some time to run or stop.
CV 3: 64, accelleration rate
CV 4: 64, breaking rate
And enable the custom speed table.
CV 25: 16, custom speed table
But before the custom speed table will work we had to set the appropriate bit in cv 29.
CV 29: 18, speed table enable
Since I use a Roco Multimaus as my DCC system I need to press a shift key to access F-keys 11 – 20. Therefore I swapped the F7 and F11 key which is done by cv 41 & 45.
CV 41: 128, F7 key is break
CV 45: 8, F11 is dimmer
In order to breake the train when I push F7 we had to put in the brake rate in cv 61.
CV 61: 129, breake rate for F7 key is 32
Next we have to tell the decoder it’s dealing with an articulated engine, that means eight chuff’s with every wheel rotation. I also give it some slip rate, so the chuff’s are out of sync so now and then.
CV 112: 97, dual air pump, medium slip rate, articulated
With cv 115 we assign the whistle for the locomotive
CV 115: 6, whistle
Since I don’t use a cam I have to sync the chuff’s with the wheel rotation by putting some value in cv 116.
CV 116: 180, chuff rate
To match the speaker size with the build-in equalizer set cv 153.
CV 153: 2, equalizer
To make the locomotive automatically make a steam blowdown after a stop, set cv 198.
CV 198: 16, auto steam blow down
The next cv’s you have to set to get your locomotive run very slow. Look at the ‘run slow’ explanation further on.
CV 209: 3, Kp Coefficient
CV 210: 10, Ki Coefficient
If you use the custom speed table, you can set it as I did, but of course you can also put your own value’s in cv 67 towards cv 94.


Custom Speed table:
CV 67: 1
CV 68: 3
CV 69: 5
CV 70: 7
. (steps of 3 per cv)
CV 91: 49
CV 92: 51
CV 93: 53
CV 94: 55
All others cv’s are default.


Run (very) slow
The Tsunami has a great BEMF control system, but, like all finely tuned items, it needs to be compatible with your loco. Here’s how you get them happy together.
Turn Off any speed tables with CV29
Set CV2 to 0
Shut off momentum (CV3 = 0; CV4 = 0)
Go to Programming on the Main
Set CV 209 to 0
Set CV210 to 0
Set the loco moving forward on speed step 1 (128 step mode recommended)
Adjust Kp (CV209) until the loco just moves, very slowly – may be jerky
Adjust Ki (CV210) until the loco smoothes out
If you want EXTREME low speed control, you can adjust from the above settings. I suggest that you reduce CV210 by 1 and then adjust CV209 up until you get movement.
Once you have done the above, you can adjust the steam chuff rate to match the wheel rotation by:
Set a medium slow speed on the loco – about step 10
Adjust CV116 for the proper chuff rate(8 chuffs per revolution for articulated locos)

The sound will be in sync for this speed step only – if the loco runs slower, it may fall off – much faster and you won’t be able to count the chuffs relative to wheel rotation. Find the best balance!

Reset momentum as set before.

CV 3: 64, accelleration rate
CV 4: 64, breaking rate

Restore speed tables and you’re done!

CV 25: 16, custom speed table

Some extra’s to download

DCC for beginners
DCC for beginners
Version: 1.0
168.8 KiB
Tsunami Steam Users Guide
Tsunami Steam Users Guide
Version: 1.0
2.0 MiB
Tsunami Technical Reference
Tsunami Technical Reference
Version: 1.0
2.2 MiB