[sennapod]

Can I extend this questions a little bit ? As well as the physical considerations, are there better (more 'powerful' decoders for 'larger' engines?. eg ones which can enable a higher top speed?
For example - I have just fitted Bachmann EZ-command 2-function chip (36-552) into a old Hornby Britannia loco/tender. Under DC control it was a great runner with a fantastic top-speed (and usually lots of wheel spin !) - but under DCC it just about reaches half its old DC maximum.
The rated motor output of the decoder is 1A - so are there decoders with more output which might enable a 'boost'?
(I have cleaned all the wheels and the track - and other locos run well)

 

[sennapod]

Thanks Zmil, richard and dwhite4dcc

all useful stuff. I'm using a Hornby Elite v1.3, haven't measured my track voltage (though it is a new layout with droppers onto a main power bus every 1m or so - so delivery should be good). I'll try exploring the CV's as sugested and see what happens.