# Speed loss



## JerryH (Nov 18, 2012)

I have 3 locos that all ran way too fast on DC full throttle. Two now have DCC sound decoders installed and run way slower at 100% throttle. It is less than half of what they did on DC. The third has a non sound decoder and it runs at about 75% of what it did on DC. Is it normal to see this kind of performance loss on DCC? I have checked the DC supply voltage and it is good. I have checked the rail voltage and it right as well. There seems to be no overheating as they will run with heavy loads without shut downs. The 2 sound equipped do not gain any actual speed above 50% throttle settings even though the sounds step up. The non sound does gain speed above 50%. Digitrax snd, Tsunami snd, and Bachmann non sound decoders. The low speed performance is much better than DC.


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## rrgrassi (May 3, 2012)

You are going to need to read the CV's. You cannot do that in DC power mode. My Tsunamis have the running mode in DC turned off, so they will not run in DC. Also the DCC circuitry will consume more power in DC mode, and slow the locomotive down. It's not the power going to the track, it's what the DCC decoder is feeding the electric motor. 

Except of course, when you turn the power off, or run at a lower throttle speed.


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## mopac (Feb 24, 2011)

That seems to be normal and common to be slower on dcc. Not sure why. My dcc puts about 14.5 volts. I think a dc train transformer peaks at about 18 volts. That would account for some difference. Maybe the decoder uses some of the power. Try playing with the speed tables.


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## NIMT (Jan 6, 2011)

Yes it's normal for a DCC equipped engine, epecially a sound one to run at a slower speed on a DC layout, switch to DCC and it will speed right back up.


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## JerryH (Nov 18, 2012)

I tested these when everything was strickly DC only. Then the conversion to DCC was done on the layout and the locos and tested again. So it seems some loss of speed is normal. BUT, 50% or more seems a lot of loss due to sound!


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## NIMT (Jan 6, 2011)

Your having a 50% loss on DCC? Yea that's wrong.
I'm still looking over your DCC roster, maybe I'll find something there for you to go off of.


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## JerryH (Nov 18, 2012)

Yep, I think something is amiss.


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## JerryH (Nov 18, 2012)

I switched the motors between the 2 identical F units and the speed differential stayed with the decoders not the motors. So it appears there is a severe loss in top speed is associated with the sound decoders. My DCC rail voltage is 14.2 on the 200vac scale. The sound and actual speed does not increase beyond 50% throttle on the digitrax sound decoder. The non-sound bachmann decoder does increase actual speed. The tsunami decoder increases the sound rate but not actual speed above 50% on the 4-8-4. The 2 F units ran about the same speed on DC before the DCC conversions. All three locos run considerably slower on DCC at 100% than they did on DC. If the rail voltage is 3.5 volts less than the DC was, that could account for the overall speed loss but why the lack of speed increase with the sound decoders above 50%? Is 14.2vac rail voltage too low? I have played with the speed tables untill I am really mad with no apparent effect on speed matching.


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## NIMT (Jan 6, 2011)

Jerry,
I looked over your roster file and I think I see the problem.
All your CV setting are all over the board, easy mistake to make.
I would suggest a reset and start from ground 0.
Another note:
By looking at the decoder types your using you will have a snowballs chance in Arizona of matching up the engines speeds.
For example the 2 F units need compatible decoders. Soundtraxx is the only manufacture that makes sound and non sound decoders that are speed matchable!
All the other manufactures will have a serious speed curve differance between the sound and non sound models.


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## JerryH (Nov 18, 2012)

Never could see any difference playing with speed tables. However I came up with a solution to matching the F AB units which was my main problem. I took the non sound unit (lots of speed) and made it the A unit. I took the sound decoder(low speed) and made it the B unit. Also in the B unit, I removed the weight, motor and worm gears. I joined the 2 decoders as a consist. The A unit has plenty of speed and I didn't need the extra power of the B unit power to help pull the train. Not a proper solution but the train works as I like it. Plenty of speed and sounds and no more headaches. While I was at the train shop, a customer brought in a brand new Proto 2K and testing in on the layout there, it can't go very fast as well. It looks to me that these sound decoders really drop the power available to run the motor. I also observed a speed match between a sound and non sound pair of sd40s. While they were matched at moderate speed, the speed table was way skewed slower on the non sound compared to the sound equipped unit. My odd consist passenger train can now run 84 scale speed flat out and my 4-8-4 can run 70 flat out. Those are within realistic max speed expectations.


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## NIMT (Jan 6, 2011)

It all matters on what decoder you use! The soundtraxx sound and non sound decoders will allow engines to run at full speed and full power.
And Proto 2k are slow always!


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## JerryH (Nov 18, 2012)

4-8-4 bachmann on DC 111mph on DCC with Tsunami 70mph


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