[Trivia] DMU with longest range.

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Class172

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Having seen the related thread regarding which train would go farthest with unlimited fuel etc., it made me ponder the following scenario:-

Every train (DMU/DEMU) is filled completely with fuel, then driven along an infinite track with no gradient. Given no other external factors, which train would run out of fuel and stop first under the following speeds?:
  • At maximum operating speed
  • At a set speed of 70mph

Which are the most fuel efficient trains, I would assume some of the most modern DMUs such as a Class 172??
 
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Geeves

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Well the idea of modern DMUs being better on fuel is a misnomer already, 185s for example are terrible on fuel. I think 15x on a full tank have a range of around 1500 miles, though I could be wrong, so i guess if it was running constantly 1700 miles?

The figures Ive seen in the past show a 142 will do roughly 2 to 3MPG driven gently, a 156 about 2MPG and similar for 158s. 185s about 0.5MPG at a push.
 
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DXMachina

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No insight or knowledge but.... At 70 I bet best economy would be either a 100mph DMU or a diesel intercity set such as a voyager, just because it is a speed at which engines designed for high speed use would be barely even strained
 

Nym

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I'd say a 15 car voyager tbh. You could run at 70 with 2 or 3 generators running, and proberbly sustain it with only 1, so you have 15 generators worth of fuel to chew through only using one or two.
 

Goatboy

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I would have thought modern trains would be really bad at fuel economy, due to the ever tightening and impossible to meet emissions standards?
In theory though the emission of CO2 is proportional to the fuel burnt.. therefore one way of reducing emissions is to use less fuel.
 

O L Leigh

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CO2 emissions are not measured at the outlet ports but at the point the exhaust enters the atmosphere and, as Nym says, CO2 is only one part of the equation. There are also carbon particulates and other nasties that are measured.

As no-one has yet come up with a diesel engine suitable for use under a train and clean enough to meet current (and foreseen) emissions standards, the only way to ensure that emissions standards are met is to stuff the exhaust system full of diesel particulate filters, catalytic converters and the like to ensure that what comes out of the exhaust pipe is fresh air and smells of daisies. The problem is that all of these constrict the flow of the exhaust gases meaning that the engine has to work harder and burn more fuel simply to overcome the back-pressure that all of these devices introduce into the exhaust system. Therefore, clean emissions should not be confused with good fuel economy.

However, Nym is confused about Voyagers. How do you get the fuel from the 12 dead cars into the 3 that are running? The function of the range of a vehicle is the amount of fuel available to it and how efficiently it uses that fuel. Fuel carried in cars that are not running is just dead weight unless it can be used.

O L Leigh
 
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route:oxford

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Given that you are only going to use enough fuel to combat wind residence and component friction...

Isn't there a possibility that you run out of coolant or lubricant/oil first?
 

O L Leigh

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Easy. You stop one generator and start another.
Are you saying that it is possible for the driver to selectively stop and start individual engines on the move from the cab, or is that a guess? Should I ask someone who signs Voyagers?

O L Leigh
 

TDK

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The basic fuel range for units I know of is:

14x 800 miles
15x 1500 miles
175 2000 miles
--- old post above --- --- new post below ---
I'd say a 15 car voyager tbh. You could run at 70 with 2 or 3 generators running, and proberbly sustain it with only 1, so you have 15 generators worth of fuel to chew through only using one or two.
Even if you have one or more engines not running this will have to be rotated or one will run out of fuel so the range would be based on an individual coach and not the set.
 

Class172

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At 70mph+ surely the 22x units gain great advantage from their sloped fronts and aerodynamic properties
How much difference does it make at that speed, since the value of drag is dependent on velocity more than anything else?
 

krus_aragon

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At 70mph+ surely the 22x units gain great advantage from their sloped fronts and aerodynamic properties
The esperience with streamlining in the steam era was that it didn't make much difference below 100mph: it was removed from the LMS's Coronation class to make maintainance easier, as the efficiency gains weren't worth the faff.
 

zn1

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technically as the hsts are Demus, or they were as fixed form units when built , the longest non stop job was aberdeen - penzance wasnt it on the old XC jobs ?? Im not sure if a voyager has ever done this job...
 

Bayum

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technically as the hsts are Demus, or they were as fixed form units when built , the longest non stop job was aberdeen - penzance wasnt it on the old XC jobs ?? Im not sure if a voyager has ever done this job...
It's still a timetabled 22x service.
 

WestCountry

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The esperience with streamlining in the steam era was that it didn't make much difference below 100mph: it was removed from the LMS's Coronation class to make maintainance easier, as the efficiency gains weren't worth the faff.
Of course 1930s streamlining was more about aesthetics than efficiency, and steam locos needed far more maintenance than modern diesels, so that comparison probably isn't very applicable. :p
 

HSTEd

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Are you saying that it is possible for the driver to selectively stop and start individual engines on the move from the cab, or is that a guess? Should I ask someone who signs Voyagers?

O L Leigh
I am pretty sure I felt generators switch off while the train was rolling in my one trip on a Cl222.
I can't see any reason why you couldn't, since the genset has no need to know if the train is moving or not, it will be a software issue if anything.
 

ash39

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Should voyagers be part of this discussion, as they are diesel electric which is obviously a lot different from a DMU and I would expect more efficient too.

I bet there's not much in it. Pacers will use less due to their weight but will have smaller fuel tanks. Sprinters will use a bit more but have bigger tanks.
 

jon91

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Should voyagers be part of this discussion, as they are diesel electric which is obviously a lot different from a DMU and I would expect more efficient too.

I bet there's not much in it. Pacers will use less due to their weight but will have smaller fuel tanks. Sprinters will use a bit more but have bigger tanks.
A Voyager is still a DMU, unlike a HS-I'm not opening that can of worms... :lol:
 

ash39

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Well it's a multiple unit powered by diesel yes, but surely it's a DEMU not a DMU which the thread states?!

If they count, surely they would be top of the pile. More aerodynamic than a slab fronted unit, diesel electric transmission and I would have thought range would have been a high priority at the design stage due to the nature of the routes they're deployed on.

Also it depends if we're counting actual range or potential range. Some routes will extract better economy from engines, much like in cars. Lots of stop start, gradients etc all make a big difference.
 

theageofthetra

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How far could a fully fuelled Hastings diesel go? Didn't they do some epic rail tours in the 80's with 6 power units to get them over the hilly bits?
 

Class172

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Just to clarify, we are including all DMUs in the discussion, so voyagers etc. are included.
 
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