fuel consumption

[Gary H]

62613, on 15 Nov 2014 - 09:27, said:

I noticed in the last video that the exhaust was pretty dark whilst the locos were in the tunnel, but as soon as they were in the open, the exhaust cleared. Is this something to to with a shortage of air in the the confines of the tunnel?

45125 is spot on.

The locomotives are basically using up all the oxygen in the tunnel and it makes them smoke very badly.

The worst example I've ever seen is "The black fog of Blossburg" on YT. It has so many engines on the front middle and back, the whole train completely disappears in smoke!

[Gary H]

I remember being told a long time a go that a class 50 done about 1 mile to the gallon!

[DavidBird]

In the book "The Deltics -  A Symposium" (2nd edition, Ian Allen, Shepperton 1977, p11) the fuel consupmtion of the prototype Deltic, on a test run over the S&C with 20 coaches, 642 tons, is quoted as 1.27 gal/mile.  I also seem to remember a quote along the lines of "0.8mpg, which was pretty good considering the power developed" - but I can no longer find this.

[skipepsi]

I think the old Ark Royal the one with boilers not Concorde engines used to manage on 4 gallons per yard or some such ridiculous figure.

[jjb1970]

Comparing specific fuel consumption figures between eras is problematic. You might imagine that electronic engine management and the techniques associated with such technology such as variable timing variable would make the engines more efficient and it does. Unfortunately tightening NOx emission limits and an aversion to after treatment or techniques such as EGR (at least on the earlier stepped reduction phases) led engine builders to retard timing and suppress temperatures in the combustion space which reduced NOx but also reduced efficiency. So there is a paradox that in engines built in the 1990's and 2000's the older versions can often actually be better on fuel consumption.

The is also the matter that engine efficiency is only one part of the energy conversion processes of a locomotive, there are also electrical efficiencies which can vary between different designs. And there is the question of energy density, in some applications reducing weight and footprint with a very highly rated engine is well worth a sacrifice in specific fuel consumption. And you can do an awful lot in terms of package efficiency, reducing the wasted heat rejection to air and water also on a train you are obviously much more limited than in some applications. Not to mention hybrid technologies, regenerative braking etc. On a high speed train the aerodynamics are very important too, generally more so than weight at least in terms of power demand.

[peanuts]

Comparing specific fuel consumption figures between eras is problematic. You might imagine that electronic engine management and the techniques associated with such technology such as variable timing variable would make the engines more efficient and it does. Unfortunately tightening NOx emission limits and an aversion to after treatment or techniques such as EGR (at least on the earlier stepped reduction phases) led engine builders to retard timing and suppress temperatures in the combustion space which reduced NOx but also reduced efficiency. So there is a paradox that in engines built in the 1990's and 2000's the older versions can often actually be better on fuel consumption

 

this is why so many modern truck engines run with adblue ( basically urea ) aditive as it lowers the emmisions with out the need to retard timing still means figures of around 4-6 mpg when climbing from Rochdale to saddleworth up the M62 but normally around 10-12 to the gallon for large trucks running at 56mph or less . my Isuzu 7.5 tonner returns between 16 & 20 mpg depending on how heavily loaded  . maybe a good comparison would be a 142/3/4/ against a modern bus especialy the diesel electric hybrid  ones running under the green bus banner around manchester ?

[Clive Mortimore]

Hi jjb

 

To add to your list, the geezer pulling back the power handle. Even the same driver with the same locomotive on the same duty will drive it differently on Tuesday compared to how he did on Monday.

[decauville1126]

If the bus industry is anything to go by, the average AEC engined bus will do a minimum of 8mpg; on a long run this can go up to 14mpg.

 

The trusty Routemaster came into the 8mpg bracket in town, but the Cummins engine refurbs can do well over 15mpg on a long run. the RML is the best for passenger/weight ratio of any bus, with an unladen weight of around 7760kg for 72 passengers. Modern box buses barely achieve 4mpg, with an unladen weight of about 11 tonnes.

 

Things such as cataclysmic converters and fuel management mean that Euro-whatever spec engines use far more diesel than their older counterparts so it really makes me wonder why they bother. 15mpg should equal say 100 gm of poisonous filth pumped into the atmosphere; 4mpg means about 400gm of slightly cleaner filth pumped into the atmosphere. 

I spend the bulk of my working time behind the wheel of a doubledeck Scania - even on the newest 64-reg ones I'm 'good' if I can average 7 to 8mpg over a shift!

 

As to the comment above as to "why they bother" it's possibly so that the operator can market their 'green' credentials whilst hiding the true amount of emissions. 

[roythebus]

According to my son the Southern diesel fleet does 1.4litres per mile; can anyone convert that to mpg? But then he says they spend a lot of their 20-hour day idling at termini, cleaners, pre-leave depot prep etc.

[stovepipe]

About 3.2 mpg ish.

[jjb1970]

Larger engines tie fuel consumption to time and power as it is the only meaningful measure for the engine itself on fuel figures, hence g/KWHr (SOFC) is the accepted standard. These engines are now being fitted with selected catalytic reduction (what the adblue is for) and exhaust gas recirculation to knock out NOx and we are seeing a recovery of efficiency. Particularly with SCR it allows the option of tuning for absolute peak efficiency without worrying about NOx, that condition is normally ideal for particulate and carbon monoxide emissions too which went up as manufacturers went for the easy option on reducing NOx.

And the point is well made by Clive Mortimore that ultimately how an engine is used is the critical variable. As with a car the actual fuel consumption varies with use, normally big engines are tuned to delivery peak SOFC at high loads, some might struggle a bit with the idea that it is almost always more efficient to use more fuel in absolute terms but to do more with that fuel.

On emissions there are two things that get conflated, carbon emissions and other greenhouse gas emissions and the more established atmospheric pollutants associated with public health, acid rain etc. Whilst it is true that if looking at carbon/GHG emissions then absolute emissions quantity means that playing with NOx, SOx etc is not important, when looking at these other pollutants it is the concentration in exhaust which is important as if they have been removed from the exhaust then they've been dealt with. Engine builders now have a problem that when testing engines they are often actually cleaning the air which makes emissions testing awkward in terms of  emissions verification if the inlet air is already in some cases above the emission limit.

[lankyphil]

this is why so many modern truck engines run with adblue ( basically urea ) aditive as it lowers the emmisions with out the need to retard timing still means figures of around 4-6 mpg when climbing from Rochdale to saddleworth up the M62 but normally around 10-12 to the gallon for large trucks running at 56mph or less . my Isuzu 7.5 tonner returns between 16 & 20 mpg depending on how heavily loaded  . maybe a good comparison would be a 142/3/4/ against a modern bus especialy the diesel electric hybrid  ones running under the green bus banner around manchester ?

 

Gotta agree there. I get over 9mpg from a 64 reg R450 (AdBlue), whereas in a 12 reg R440 (EGR only) I struggle to get over 8 some days (Supermarket work in towns). The AdBlue motors are a lot more reliable than the EGR fitted ones apparently.

[great central]

 

 

this is why so many modern truck engines run with adblue ( basically urea ) aditive as it lowers the emmisions with out the need to retard timing still means figures of around 4-6 mpg when climbing from Rochdale to saddleworth up the M62 but normally around 10-12 to the gallon for large trucks running at 56mph or less . my Isuzu 7.5 tonner returns between 16 & 20 mpg depending on how heavily loaded  . maybe a good comparison would be a 142/3/4/ against a modern bus especialy the diesel electric hybrid  ones running under the green bus banner around manchester ?

 

Does that mean if I pee in the tank of my diesel car it'll produce less emissions and use less fuel

[APOLLO]

 

Does that mean if I pee in the tank of my diesel car it'll produce less emissions and use less fuel

 

Probably

 

 

Brit15

[AMJ]

Does that mean if I pee in the tank of my diesel car it'll produce less emissions and use less fuel

GC I think that it will cause issues to the engine as per the episode of Porriage when Mr Barker does exactly that!  If life was as simple as that!

 

I could be tempted by red diesel apart from the hefty bill if HMRC dip your tank.

 

I often wonder how much fuel is not used when the modern vehicles auto stop start the engine when idling at stop lights.

[Edwin_m]

GC I think that it will cause issues to the engine as per the episode of Porriage when Mr Barker does exactly that!  If life was as simple as that!

 

I could be tempted by red diesel apart from the hefty bill if HMRC dip your tank.

 

I often wonder how much fuel is not used when the modern vehicles auto stop start the engine when idling at stop lights.

Yes, but it wouldn't be using fuel or producing emissions though. 

 

Illegal use of red diesel is tax evasion and in my view should justify an "episode of Porridge". 

[peanuts]

 

 

I often wonder how much fuel is not used when the modern vehicles auto stop start the engine when idling at stop lights.

one wonders how much the strain of restarting the engine at every stop is putting on the starting circuit believe some are even using the altenator as a motor to help share the load during stop.start precedures other wise can see an increase in starter motor & battery  changes which would ofset any gains from lowered fuel consumption

[skipepsi]

one wonders how much the strain of restarting the engine at every stop is putting on the starting circuit believe some are even using the altenator as a motor to help share the load during stop.start precedures other wise can see an increase in starter motor & battery  changes which would ofset any gains from lowered fuel consumption

I think you are right in thinking over a period of ten years there would be more expensive repairs required than fuel saved, but who actually thinks long term, politicians will love them for the reduction in fumes in cities now.

[Edwin_m]

I think you are right in thinking over a period of ten years there would be more expensive repairs required than fuel saved, but who actually thinks long term, politicians will love them for the reduction in fumes in cities now.

Thinking long term might involve considering the number of people affected by particulates and pollution.  If the link below is even a little bit true it is quite alarming. 

 

http://www.bbc.co.uk/news/uk-england-london-20664807

 

So perhaps a few extra repairs is a fair price to pay for the privilege of driving in the city? 

[Clive Mortimore]

Cars with auto stop are a (not RMweb word) when stuck behind them at the lights. Get three of them in front and they are a across but you get the next red light.

 

 

 

Worse than old boys who put on their hand brake at each light or junction.

 

I may chear up later today

[Titan]

I am not convinced about stop/start.  From time to time with my job I get to drive a variety of modern hire cars. Never had one with stop/start, but I did have a few which could tell you your fuel consumption. which when stationary changed to gallons/hour. When stopped this was typically 0.2 gallons/hour or about 2p per minute at today's prices. Now before stop/start was invented, I was told it was only worth turning off your engine if you were going to be stationary for more than 30 seconds, as the fuel used to restart the engine (including the extra required to recharge the battery) would be more than that saved. Stop/start does not know how long you will be stationary, and in moderate town driving most of the time you halt will be less than 30 seconds.  I was behind one in a traffic jam on the M6 recently, with the traffic moving forward sporadically. Rarely was the traffic completely stationary for more than 30 seconds, but with the stop/start nature of the traffic the starter must have been getting a real work out on it! So it is quite possible that depending on your driving conditions stop/start on average could increase emissions!

 

Which brings us on to the next issue, we know that by far the largest amount of wear is done to the engine on starting, particularly when cold. I bet these stop/start cycles do more than 4p of wear to the engine for every 2p of fuel saved.  In fact an engineer friend of mine said that you would get a far more accurate indication of engine wear on a car if instead of mileage it recorded the number of times the engine was started!

 

And a more minor issue, in this weather I want the engine to warm up as quickly as possible, so there is no way that I would want stop/start to work before the engine is fully warm, apart from the extra wear it would cause I want the heater to work to the max!

[skipepsi]

You do have to opt in to the stop/start 'eco' setting but as the car I drive at present has a push button handbrake any hills I end up holding it on the clutch to prevent roll back when setting off. Unless the car is an automatic I won't be leasing a push button handbrake car again.

[peanuts]

another thing to think on is the effect of stop start on bearings etc you come off a long high speed run on the motorway and into town and typicaly get into a gyrater traffic light sytem strait away so tthings like the turbo bearings which are nice and hot and will continue to spin after engine shut down are no longer recieving oil under pressure from the engine cant be good for the bearings 

[Gary H]

peanuts, on 17 Nov 2014 - 18:56, said:

another thing to think on is the effect of stop start on bearings etc you come off a long high speed run on the motorway and into town and typicaly get into a gyrater traffic light sytem strait away so tthings like the turbo bearings which are nice and hot and will continue to spin after engine shut down are no longer recieving oil under pressure from the engine cant be good for the bearings 

That's a valid point!

Turbo's get extremely hot and when you stop the engine after its been worked hard (or even cruise on the motorway for that matter) it suffers from heat soak from the turbine side (very hot exhaust) causing carbon to form on the sleeve bearing of the turbo as the oil overheats because of shut down. These conditions  are ripe for turbo bearing failure! Cue a 2 grand bill for a new turbo.

The other thing that bothers me about this stop-start nonsense is wear to crankshaft shell bearings. They obviously have zero oil pressure every time you start the engine, its only for a couple of seconds but what's going on with with these soft white metal bearings inside a hot engine at every set of lights / stop start traffic every day!!

[Guest]

I am not convinced about stop/start.  From time to time with my job I get to drive a variety of modern hire cars. Never had one with stop/start, but I did have a few which could tell you your fuel consumption. which when stationary changed to gallons/hour. When stopped this was typically 0.2 gallons/hour or about 2p per minute at today's prices. Now before stop/start was invented, I was told it was only worth turning off your engine if you were going to be stationary for more than 30 seconds, as the fuel used to restart the engine (including the extra required to recharge the battery) would be more than that saved. Stop/start does not know how long you will be stationary, and in moderate town driving most of the time you halt will be less than 30 seconds.  I was behind one in a traffic jam on the M6 recently, with the traffic moving forward sporadically. Rarely was the traffic completely stationary for more than 30 seconds, but with the stop/start nature of the traffic the starter must have been getting a real work out on it! So it is quite possible that depending on your driving conditions stop/start on average could increase emissions!

 

Which brings us on to the next issue, we know that by far the largest amount of wear is done to the engine on starting, particularly when cold. I bet these stop/start cycles do more than 4p of wear to the engine for every 2p of fuel saved.  In fact an engineer friend of mine said that you would get a far more accurate indication of engine wear on a car if instead of mileage it recorded the number of times the engine was started!

 

And a more minor issue, in this weather I want the engine to warm up as quickly as possible, so there is no way that I would want stop/start to work before the engine is fully warm, apart from the extra wear it would cause I want the heater to work to the max!

 

i drive a Ford Galaxy 12 plate with stop / start, it only operates when the engine has warmed up, you can also turn it off...and to add insult to injury it also has an electronic handbrake! however with 112k on the clock and averaging over 50, no complaints from me.

 

Regards

 

Gary