# speed matching with different decoders?



## lownote (Jan 3, 2008)

This is for any of you DCC experts out there.

I spent a bit of time today messing with the USAT S4 I picked up at the Fall ECLST. It has a NCE 408SR in it and a phoenix sound card. I want to consist it with an Aristo RS-3 that has a QSI decoder in it. 


Is there any easy way to do this? I adjusted start voltage, max voltage and mid voltage on the NCE decoder so it runs very close to the exact speed of the RS-3. That part's easy. The harder part is momentum--they accelerate and deccelerate at different rates. On the 408SR, in the S4, I set CV 3 and CV 4 to the same values they are set to on the QSI decoder in the RS-3. Any tips on how to get two very different decoders to behave the same way? I like the way the RS-3 runs, and I'd like to match the NCE 408SR to that. If anyone has any ballpark guides for setting momentum, I'd love to hear about it.


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## George Schreyer (Jan 16, 2009)

The QSI decoders have a longer momentum than other decoders for the same setting. When I set them up, I do it on parallel tracks so that I can see the impact. It can take some diddling to get a QSI decoder to match other decoders but it can be done. 

Start with zero additional momentum on the QSI and adjust the other loco to sort of match that as a starting point. If you are going to consist the QSI with the other loco, then make sure that only one of them has BEMF enabled.


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## Greg Elmassian (Jan 3, 2008)

I know that disabling BEMF during consisting has long been a recommendation, but I leave it enabled on QSI's and do not have problems. If you disable BEMF on the QSI, then many of the sound features are lost. 

I often run 3 E8's consisted and they run fine. Maybe these newer decoders are somewhat smarter in their BEMF implementation. 

Regards, Greg


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## lownote (Jan 3, 2008)

I'd like to keep the BEMF on the RS-3, which will be the lead loco and which has the QSI card. The 408SR doesn't have BEMF, so I'll monkey around with the momentum settings and see what I can come up with. It works fine now, but of course what I want to see is two locos moving in perfect tandem


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## aceinspp (Jan 2, 2008)

Seeing as I have the same set up in the S-4 I'd like to know what your final settings are for the RS3 and S-4. Later RJD


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## Greg Elmassian (Jan 3, 2008)

I think it would be pretty simple to just run them 6 feet apart, and then take the speed to zero fast... do the same on acceleration. 

You can tweak both decoders on the main... by the way, do NOT use the momentum button, set CV3 and 4 manually, so you know what you are getting, the momentum button is more "coarse" than what you want, and it sets both accel and decel at the same time. 

Regards, Greg 

p.s., you have to turn voice confirmation off on the QSI if you want that button to work from the NCE... the QSI will not process the next command until it's finished talking, and the NCE sends the CV3 and CV4 commands back to back.


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