I asked this (OT question!) on the TFW 769 thread, but I think it’s more likely to be answered here. How/why did the 319’s gain such a poor reputation performance wise at Northern? I’ve seen it mentioned several times but it doesn’t make sense when they were fine on Thameslink (occasional slipping aside). Compared to a pacer or a 15X they should feel rather quick? I realise they won’t match the acceleration of a 323 though, maybe that was the issue?
Ever since the 319s were transferred to Northern, there have been posts about how bad these 'London cast-offs' were, not focussing only their internal accommodation shortfalls, but alluding to their terrible track performance.
All of this was in the face of their 20+ years of heavy use on a 100mph mainline in the south-east where failures and poor running would have had an immediate effect on their route's services. Their drivers were capable of keeping within tight paths such that the services worked together.
The same hardware with an additional mass of two genset's that together weigh less than a full seated passenger load in two cars are now being supplied about 60% of their power which will inevitably, reduce their acceleration relative to their EMU performance. But on a straight run, their terminal speed will eventually probably reach the sort of speeds that they achieved during testing, i.e. c90mph. In addition, adequate performance can be delivered across the speed range because there is little loss of torque with a DE transmission and an almost flat power curve.