It isn't normal. Although the trains are 20 years old now, when the trains were new for the first ten years, there was never this idling racket. There have been so many engine modifications, it now sounds ridiculous. I'm aware of a noise complaint, 1am, 300 metres from the line by several nearby residents. The local nightclub was initially blamed for the "awful constant booming noise"... turned out it was a 185 at a signal, caught up in an emergency possession for 45 minutes. I know Network Rail have now started paying attention to this, not just in our local area. The huge exhausts seem to be part of the noise problem.
Well, I take back what I said then.
You're kind of right in that many of them do this, and it isn't unexpected, but the underlying point is that Siemens didn't design or build them to sound so ridiculous. Even more ridiculous than me.
What do you mean a unique hydraulic diesel engine ?
And also used by 180s, 220s, 221s and 222s
Maybe when the Driver puts the 185 into Forwards, the engines change how fast they're revving, similarly to how the engines on 220/221s very notably rev up a bit when the Driver puts them into Forwards, even when they're idling?
Except that in this case, two simultaneous different rpm signals (an increased one and a non-increased one) could be interfering?
