The Emissionary Position: screwing the motorist the European way Everyone has heard about the diesel emissions scandal surrounding Volkswagen, but finding out what really went wrong and who is to blame is not so clear cut. John Watkinson considers the culprits: mechanical, political and virtual. Diane Keaton and Woody Allen in Sleeper Wait! Don't give your filthy VW the push, the trail …
...Should be put to MOST EFFECTIVE use.
* Against NOx emissions.
* In the most affected regions.
But don't assume that fixing the VW fleet is the best way forward.
Perhaps city buses with heavy diesel engines would be a more effective target. Larger realworld reductions per €£$.
Opportunity knocking. Somebody needs to break out a spreadsheet to optimize the way forward.
Thumb down...
Okay, let's have a narrow view based on ideology and squander the opportunity. So retrofit millions of VWs that'll be rust in about ten years. Not the city buses that run 16 hours a day and emit vastly more NOx.
Yep, let's take the LEAST EFFECTIVE action.
#Humans_are_doomed
> Jet fuel ≅ diesel fuel
Very curiously this is actually not true.
There are diesel engines for light aircraft, and they don't run on ordinary diesel fuel, they are designed to run on Jet-A. They do get better economy, even when measured as energy per unit mass, rather than by volume. What they are not is common. Continental for one, are in the midst of bringing one to market.
You can happily run an unmodified diesel engine on Jet fuel (I've done it, and US military hummers run on it almost exclusively) and you can happily put diesel in a gas turbine engine (Have done that too - one of the classic bodges is a mix of diesel and petrol in turbine helicopters if you're really in a pinch)
Most light aero engines are still using 1930s engine technology because it's difficult to homologate newer ones. This is why they have to be torn down at such ridiculously short intervals.
JET-A hasn't been on the market for a long time, but if you can find it, I'm sure your diesel won't mind it.
And the difference between Summer Diesel, Paraffin stove fuel, Kerosene, Winter Diesel, home heating oil, "jet fuel" is?
Versus Car petrol, high octane non-jet aircraft fuels etc? There is a good reason why lead is in aircraft petrol, makes the octane rating appear higher!
Whilst I see that questions have been raised over buses, none have been made over the core thrust of your point, namely: squandering the opportunity that VW's potential payout of billions actually represents.
You are right the real losers here are not the individual VW owners but society as a whole. Hence it potentially makes little sense for VW to spend billions on something that isn't either a safety or reliability issue, nor something that will move the state-of-the-art of vehicle emissions forward.
Because a key question has to be whether these old VW's once retrofitted with 'correct' software will be anywhere as clean as a new VW with current state-of-the-art emissions technology. Hence governments and VW should be spending their money on getting owners to update, which also helps to keep VW employees in work. Also because we know that VW are only the first to come clean this approach can very easily be applied to other manufacturers and may offer them a no fault way to come clean about their emissions misdemeanours...
Perhaps city buses with heavy diesel engines.
Err... Most of these already run adblue so they are fairly NOx clean compared to cars.
It is possible to make them even cleaner on other parameters (soot, etc) too. The tech has been well tested and is used extensively around Europe. It is called diesel fumigation - adding a small amount of LPG to the injection flow (AKA diesel blanco, etc). It is used on boats, buses, etc worldwide.
It improves fuel efficiency, reduces particular output roughly by an order of magnitude (before any filters take effect), but as with anything which improves diesel efficiency it also raises the NOx. If you are already adding "piss" to the exhaust that does not matter, you just adjust the amount of piss to add. It is also retrofittable.
The problem is that some governments like UK are so oil revenue addicted that they will do no anything to disallow a massive step-decrease in fuel consumption so you cannot get a fumigated diesel past a MOT in the UK and similarly, the LPG conversion guys are not allowed to do fumigations except on boats.
So the article is incorrect. You _CAN_ get a diesel to emit less off everything compared to gasoline on any metric, you just have to make it even more complex. You will be looking at 3 tanks - diesel fuel, LPG and Piss (adBlue). Similarly, if you are looking at pollution efficient vehicle that burns stuff, LPG _WITH_ adBlue is way ahead of gasoline too (switching to LPG raises NOx quite a bit). Gasoline trails all of them and once you take into account everything that is available for pollution reduction it is not any better.
The current state of diesel technology is another example that taxes corrupt everything. There we are, we take decades of research to get away from a slow, smokey, noisy and stinky 1975 Mercedes 200D/60HP engine to a 2L four cylinder diesel with 140-150HP. The latter comes with a price, approx. three times the costs of a 2L petrol four cylinder which can nowadays be brought to 130HP without turbo. A replacement *four* cylinder engine now costs $ 4000 - $ 7000 for any VW in Europe.
What do we get for the low taxing of diesel oil by most European states: Expensive and difficult to maintain diesel engines with parts prices at aviation level, NOx everywhere and fine soot, which is the real killer.
Maybe this VW scandal will be the beginning of the end of diesel cars in Europe. We better invest in general availability of 120-140 octane petrol and build engines for that, they will be clean and cheaper to produce than these dumb diesel engines, which will always burn Nitrogen due to the high temperatures and pressures involved in the diesel combustion process.
The article is great, the best i have seen on the subject.
NOX isn't exclusively a diesel issue, see my earlier comment.
The _only_ reason gasoline engines have low NOX emission levels is that lean burn technology was essentially banned 20 years ago in the USA. That ban means that petrol engines get 20% worse fuel economy than they are able to if NOX wasn't an issue.
(Lean burn was banned by US federal legislation mandating that stoiciometric fuel ratios are used at all times in spark-ignition engines. 3-way catalytic converters need this to work effectively but it's just as feasible to put adblue on petrol engines and change the type of cat in use.)
As of 2011 (latest test results available) _HALF_ the NOX in London is emitted by stationary sources - primarily older boilers.
IN 2001, they accounted for 1/3 of emissions. Vehicle-sourced emissions have halved in the last decade.
They should have reduced further but that's what the article's all about. It's extremely unlikely that VW accounts for all the rogue emissions as there simply aren't enough of their cars on the road to account for it.
Condensing boilers emit almost no NOX at all (the burn temperature is lower and much of what's left gets absorbed by the condensate). Boilers made since 2002 have emissions limits they have to comply with (it'd be interesting to see if they are playing cheat games). That puts the finger squarely on 15+ year old installations.
Reducing car emissions further won't make much difference to air quality in London. It might in places where gas/oil heating isn't widely used.
It's also worth noting that NOX levels are only problematic inside the North/South circular roads and critical within the inner London ring road: IE: All that NOX control used everywhere is to combat problems encountered in very limited geographical areas.
The same pattern is seen in most cities. Once you hit the suburbs NOX doesn't matter.
The fact that cars can cheat is only a problem if they cheat in critical zones. They have enough smarts to know where they are then they can adjust accordingly. The sensors used to detect nox levels in the exhaust can also detect nox levels in the intake and switch emissions control on/off as required.
Blanket emissions controls are a very blunt instrument and the counterpoint is much reduced power/increased fuel consumption when it's used unecessarily. Perhaps it's time to start regulating intelligent use of it.
That said, there's no good reason why diesels should be used as urban commuters. The engines will gum up quickly if used like this (which makes car dealers very happy as they do a roaring trade in DPFs).
I read somewhere* recently that older boilers were better on NOx than condensing, although worse on CO2 hence the move to switch. The reason being that the exhause on older boilers cools more slowly, allowing the NOx to degrade to something else. In a condenser the gasses are cooled rapidly defeating this process. Also I believe condensing boilers have a higher max burn temp, increasing NOx production.
*I think it was here on El Reg.
Except that when you take a balanced view of emission limits, the petrol/electric hybrids piss on diesels from a great height.
Why are we where we are? 'Cos the EU wouldn't countenance handing the playing field to the Japanese manufacturers while simultaneously rendering the billions poured into oil-burner design by the Germans and French manufacturers money down the drain.
The prospect of every fleet Mercedes purchase in year 1 being a Lexus in year 2 if the "wrong" emissions standards had been chosen caused a fair bit of lobbying effort.....
It's far, far worse than just that.
You see, ICE fuels are actually waste products of the catalytic refinery process. The very process that give us our myriad of plastics and lubricants and the various other products made from crude oil.
It's the very reason automobile inventors chose it. It was cheap because it was waste. Much like today's vegetable oil converters use waste frying oil for their cars..
Now imagine there is no longer any demands for ICE fuels. What will they now do with all that waste?
It is a very big and potentially catastrophic dilemma.
This is part of what creates the political problem.
"With respect, that is garbage. Vehicle fuel is the highest value product of refining, and determine the economics."
Just because that is the case now, doesn't mean it was always the case. Two examples:
Sawdust was a waste product of the wood industry, we now take trees and instead of machining them directly into timber planks and beams, we mill them and make chipboard, fibre board, flake board etc.
Caffeine was a waste product of the decaffeinated tea and coffee business, now decaffeinated tea and coffee is a byproduct of the caffeine production industry...
Correct. Gasoline used to be routinely dumped into rivers by the early oil refineries because it was considered useless. They were more interested in refining high grade lubricants and kerosene for oil lamps.
Er...no
Diesel engines utilise a higher compression ratio that spark ignition engines. They need to because it is the air temperature rise on compression that ignites the fuel. This means, too, that the combustion peak temperature is higher than in SI engines, and this produces more NOx, because nitric oxides are endothermic. So (with the other factors involved) it is easier to fix the NOx problem in SI engines using EGR and catalysis.
If CO2 wasn't considered to be a problem then cars would almost all be SI because the engines are simpler, lighter and cheaper, and with no need for turbocharging or supercharging maintenance is a lot cheaper too.
Was tried in the 50s because of the theoretically high specific fuel consumption compared to petrol piston engines and the then state of jet engines. But the engines were complex. Eg Napier Nomad compound engine, and turboprops worked out more effective overall.
Pre-war there was a Junkers Jumo diesel
"Are you saying the current American diesel-hating is a misplaced and belated effort to one-upmanship the Putin?"
Well, I doubt that parking a few T-34s on the White House Lawn would go down well. Especially as they would be used by the Repubs as evidence that Obama was a closet Communist.
Jet fuel is exceedingly similar to diesel. Nearly interchangeable.
.: Most large aircraft are (effectively) diesel fueled.
The mental focus on piston engines has left a rather large turbine-sized hole in the arguments being presented here on the subject of aircraft fuels.
"But the engines were complex. Eg Napier Nomad"
There's quite a difference between a light aircraft engine (70-300hp) and something like a Nomad (1100-3200hp). The research in the 50s was aimed at getting as much horsepower on the wing as with as low weight as possible because this was a fundamental limiter on the size/lifting power of aircraft.
The main reason for wanting light aircraft diesels is fuel commonality (they can burn kerosene). There are a significant number of automotive-derived gasoline engines around already and the prime advantage of those is much longer maintainence periods.
As for leaded aircraft fuel: This is because of the age of designs, as I mentioned in a previous post (and the age of the aircraft. Many light aircraft are 50+ years old with 50+ year old engines). Moving avgas to unleaded would result in receeding valves as it did with car engines until they were retrofitted with hardened valve seats. This has been done in most cases anyway (anything rated for Mogas is done already) but the aviation sector is notoriously conservative in this arena.
If you have a _really_ old engine such as a Moth, they run better on white spirit than avgas, but that's technically illegal in most countries. (The lower your fuel octane the more energy it contains but the less you can extract due to compression ratios)
Diesel engines are nasty, diesel fuel is nasty, for some reason (political lobbying?) it was "chosen" over petrol lean-burn, possibly during the Thatcher years. Good riddance. With everyone hung-up about the possible C02 threat, the real nasties such as particulates and NOx were overlooked.
Dirty business loves the focus on CO2, afterall we all emit CO2 to some extent so the blame and the costs can be evenly spread.
The car manufacturers have been cheating on their emissions but they are not the only ones, once all diesel/petrol cars are within real world tolerances we will still find that levels of pollutants are higher than models suggest, this is because everybody games whatever systems are put in place.
The financial profit motive is a strong driver.
There is nothing wrong with making a profit but perhaps we need to add a new measure to the bottom line to provide balance.
A company that posts good profits and high 'general social good' indicators could be considered more attractive and therefore valuable than one which only produces good profits but low 'general social good' indicators.
BR proposed "A company that posts good profits and high 'general social good' indicators could be considered more attractive and therefore valuable than one which only produces good profits but low 'general social good' indicators."
VW has been given 'tax' and similar breaks because they were such a 'green' company. I expect that they'll also be expected to pay some of that back.
They've had some awards rescinded.
Sucks to be them recently.
Point being... "indicators" <- LOL. What? Like vehicle emission test results? Purported fuel economy?
Diesel works best in large engines that are typically run at a fixed or narrow range of speeds. This can make the engines very low emission and very efficient.
Unfortunately cars don't run like railway locomotives. Their engines are worked at different loads and different speeds.
This is why buses and urban delivery vehicles should be running on CNG. Leave diesel for long haul work.
This whole discussion about gasoline versus diesel overlooks one quite fundamental point:
Gasoline, in the quantities used today, requires cracking of crude oil -- an energy intensive process. Diesel fuel is much closer to what we can distill off crude and takes less energy to produce. So diesel is cheaper (in price and environmental impact) to produce. Of course we see little of this because the price is a highly political issue.
It may be useful to refine gasoline in suitably modern and clean refineries and then use a more compact gasoline engine that burns cleanly in your car. I may be even more useful to burn the raw fuel in clean power plants and then use electricity instead. But to compare those things, we must consider the whole production chain from oil rig to kilometers driven.
Or we could just pretend that those electrical cars have zero emission.
You seem to think that cracking and distillation are different, but actually cracking is the same thing (it's also called "fractional distillation"). To get all the other fractions of the crude oil used elsewhere (like the propane and butane that make up LPG, and the ethane and aromatics that go into plastics and drug manufacture, and the diesel and kerosene and heavy fuel oil, the whole lot is distilled at the same time.
@ Peter Ford: Things may have changed since I got my chemical engineering degree in 1991, but certainly back then cracking was breaking the long chained (heavy) hydrocarbons into shorter (lighter) ones and destination was separating the light and the heavy fractions.
It may be possible that the processes can be combined - as I have not worked with it since, the finer details are in long tern storage.
> With everyone hung-up about the possible C02 threat, the real nasties such as particulates and NOx were overlooked.
True. However, in the quest for fuel efficiency, petrol too has become "dirtier" by some metrics - increased NOx and particulate matter. GDI engines produce surprisingly high levels of particulates (according to TUV, the EURO-V GDI's they tested were 10x higher than diesels for particulate matter), and need extra work (e.g. hybrid port injection) to make them pass EURO-VI standards. Also, modern engines (both types) producing a higher proportion of ultra-fine particulates is unpleasant.
It's been claimed that the latest petrol powered (ULEV or similar) vehicles have such clean exhaust that they'll actually "clean the air" in areas with excess air pollution.
This assumes that their real world emissions are reasonably aligned with the purported emission levels.
I've seen this factoid mentioned in various places. I assume it's true at least in the extreme cases.
> It's been claimed that the latest petrol powered (ULEV or similar) vehicles have such clean exhaust that they'll actually "clean the air"
Saab made that claim ages ago (1980s? Can't remember).
As an aside, the fact that Saab went out of business and Volvo didn't is (in microcosm) an indicator of what is wrong with the motor industry (if not more)>
..while they'd never say this publicly they thought everyone did already know. Just not possible to get the mpg..
Indeed.
No doubt they're all optimising to meet the naïve and absurd US test criteria. I fancy VW's mistake was confessing rather than spinning some "it's an olddddddd..... performance optimisation to minimise emissions when cruising down long 1 in 10 gradients on freeways passing through sensitive desert ecosystems, isn't your rigorous testing protocol aware of it?" style "prove criminal intent in court" defence and lawyering up. Big mistake. BIG BEEEEEEEELION$$$$$$$$...... MISTAKE!
Still, suppose it might have vented the pressure for giving poor gas-pedal-hustled Toyota another pass through the wringer.
But just knocking diesel because it has some characteristics that can cause problems (which have largely been solved) and then blithely saying petrol engines "will catch up" simply doesn't cut it. Each engine type has its particular emissions issues that need to be cleaned up and an advance with one fuel sort is quickly transplanted onto the other.
Frankly petrol engines have different characteristics to diesel which are fundamental to the cycles that they use. Those characteristics are why trucks use diesel and cars (that don't tow or carry heavy loads) use petrol. It isn't simply a matter of fuel consumption. It is all about torque curves and a petrol engine performs comparatively poorly in the [torque, engine size, fuel consumption, (blown) air pressure] matrix compared to diesel at various loads.
I declare an interest: I have had several diesel vehicles over the years - for the way they drive and not just for their fuel consumption. Given equal fuel consumption and similar fuel costs: I prefer the diesel.
"It is all about torque curves"
Yes and no.
Diesels work well in locomotives (where they can run at constant speed as generators) and their torque curve, giving high torque at low piston speeds, is good for load haulers which have mechanical gearboxes, where the gap between gears means that a fairly wide rev range of high torque is needed.
Recent developments in CVT are negating some of that advantage for cars because a CVT can allow a spark ignition engine to run at optimum revs over a wide range of speeds. The CVT used by small Toyotas has an effective gear range over 4:1, coupled with a small torque converter for low revs. CVT characteristics mean they work best with relatively high rev engines and modest torque, as Diesels require heavy components to convey peak torque at low speeds.
Electronic CVT for small cars and hybrids for large ones seems to give the best of all worlds, except to the people who like the feel of high torque at low revs.
Exactly what I was going to say. The article seems to assume that people have only bought diesel engines for their environmental and economic advantages, and argues that because those advantages aren't real no-one should actually want one. But anyone who drives at all regularly with heavy loads, whether that's towing a trailer/caravan or just a really full car and/or roofrack, will see huge benefit from a diesel car, especially if their journeys involve hills (the difference driving around Wales or the Lakes in a petrol or diesel car is amazing). And while a petrol Jag getting 40mpg may well be equivalent to a diesel doing 54mpg in terms of CO2, that diesel will go a hell of a lot further before needing to stop for fuel. Most people only care about pollution in a very abstract sense, but they really notice when their car struggles to get up hills and needs filling up twice as often.
Obviously there are plenty of situations where petrol wins as well, so I'm not saying everyone should rush out to buy diesels. But only looking at one or two pollutants and assuming that's the whole story is never going to get you to a sensible conclusion. After all, that's exactly how we ended up with this whole mess in the first place.
@cuddles...
One issue i have with the whole "diesels are better at hills" thing / car load / etc is... Most diesels are turbo charged and larger - i.e. 1.6 - 2.0 turbo diesels where as most petrols (in the UK at least) are 1.0 - 1.6 with no turbo...
if you take an equal size petrol turbo against a diesel turbo you will find the petrol p**s all over the diesel for speed, power, drivability, etc... have you driven an early 90s non turbo diesel? i can tell you they don't go up hills at all... Most people like the way the TURBO changes the characteristics of the engine...
that all said - i am a petrol man personally and those petrols come in V format at larger sizes... plenty of torque and up hill is not a problem - shame turbo Vs are so hard to find...
use is being restricted. Even Cross Channel Ferries are having to change to Diesel.
Military Vessels make up a small proportion of all Marine traffic so forcing them to change won't have too big an effect.
Now if every container ship and oil tanker was forced to change then the effect would be a lot greater but personally, I'd look at getting them to stop dumping plastic into the sea first.
"...I'd look at getting them to stop dumping plastic into the sea first."
BINGO.
There should be a flat $50 fee for any ship to offload their trash at any port. And a flat $50,000 fee if they mysteriously don't have any.
Of course lost fishing gear makes up a large fraction of plastic at sea.
Think you will find that ferries typically run 'medium speed' diesels with variable pitch props as against bigger deep sea ships which run low speed diesels (90-130rpm 2 stroke reversible). It is a much better system for short trip rapid turnaround vessels.
The low speed ones use higher grade fuel for manouvering when decent response is required say in port, but once up to speed at sea they switch to 'bunker oil'. Which is far less refined and hence hugely cheaper.
So by all means run cleaner diesel. But your import costs will rise on all your lovely chinese imports.
Also AFAIAA large ships are hugely more efficient per tonne/mile carried than any alternatives.
Steam is great for power efficiency but the cost for making it is high due to inefficient boilers and hence few if any steam turbine ships are about today.
Not that as an ex navigator I know much about engine rooms :-)
There are some rules for large ships in some places. East of Falmouth heading into the English Channel, they're not supposed to burn the bad stuff, so there's a bit of business to be had there providing better-quality fuel to those ships that arrive without any. Possibly it's cheaper for them not to carry it from far away places.
"Now if every container ship and oil tanker was forced to change then the effect would be a lot greater "
At least in terms of the super panama class of container ships it's been claimed that the cost of shipping a container from China to the UK is less than the cost of the trip from the port to the final destination on the back of a lorry. Using cleaner fuel would be better, but it's already cleaner than all those lorries trundling to and from the ports to load/unload the container ships.
> Bunker Fuel use is being restricted
Not for bulk long-haul shipping, I suspect.
> Even Cross Channel Ferries are having to change to Diesel.
Is there enough traffic on this (very short) crossing for that to be significant? Especially on those days when Eurotunnel is running normally? (I.e. the days when you can be across the Channel and on your way in less time than it takes to load a ferry).
"Meanwhile humongous cruise and military ships keep throwing shit around like there is no tomorrow."
Never a truer word ...
Whilst on a cruise in the Caribbean, I happened on a book shop in a Virgin Island (they are not: they are well shagged). I staggered back out into the sunshine with "Pirates Of the Caribbean": an analysis of the cruise ship world which was a bit of an eye-opener. A cruise ship does generate quite a large amount of shit - tonnes of the stuff dumped offshore.
I have noted regular brown patches in the Caribbean about 10-100cm across every say 10-100 meters. Probably just seaweed ...
(The icon is missing 2 letters)
> They might as well just ban non electric cars
Not practical - especially in cities ! The very characteristics of a city (high population density) also makes cars you have to plug in impractical (the vast majority of owners don't have somewhere to park where they can plug in). But even if you lined all the roads with charging points, it still couldn't work - where "couldn't" rally means no-one would be prepared to pay even a fraction of the cost ...
> Long-term it's likely to happen in cities
Doubt it ...
There is this teensy little problem that even if we had the generating capacity (we don't, because hippies and tree huggers have been so against building sensible capacity - ie nuclear) we wouldn't be able to transport it to the point of use. In many parts the power distribution is close to maxed out - they had to install a lot of new capacity to keep the lights on for the Olympics ! Add a lot of electric vehicles and the network would collapse - and the cost of upgrading it would be "quite significant. Not just in cash terms, but also in "dig the streets up for months" terms as well.
Financially and politically impractical until things change somewhat !
> If that electricity comes from sustainable sources, that’s fine and dandy.
Ballcocks. When you plug in ANY electric load, and I really do mean any, in this country the result is that the "taps open" a bit on a fossil fuelled power station. Our nuclear fleet (what's left of it) just runs flat out and I believe doesn't even meet baseload at night now. Renewables get special (expensive) treatment and get to supply all they can produce. And fossil fuels make up the rest - coal for the bulk of it, a load of CCGT for more baseload, and OCGT for the load following - and also compensating for the crap windmills.
So when you plug in the car, it WILL cause the taps to open on a fossil fuel station - most likely gas. No ifs or buts, that's a "will". So your lecky car is, for the forseeable future in the UK, gas powered !
Look at *any* newspaper or 'net article about people that go out to sea to extract plastic from the ocean. It's always one-tonne of lost fishing gear and 26 lbs of other waste.
http://loveforlife.com.au/files/Plastic-Ocean.jpg
http://i.telegraph.co.uk/multimedia/archive/01241/rubbish_1241490c.jpg
Pay attention and you see it's at least somewhat true.
There are a few obvious errors in TFA:
1)Efficiency - Diesels are more efficient than gasoline engines because of thermodynamics. For a given amount of heat energy released in the cylinder, more mechanical energy is obtained largely because the temperature of the working gas is higher. It has nothing to do with the nature of the fuel except that diesel is less expensive and can ignite at the higher temperatures found in the engine. Diesel fuel would not burn well in a spark-ignited engine with 10:1 compression ratios. Diesel engines have compression ratios near 20:1. The air is heated by compression (as in a bicycle-pump), and the fuel burns as soon as it is injected into the hot air. The expression for the efficiency has a major factor, (1-Texhaust/Tcombustion) where the Ts are the absolute temperatures of the working gas. The higher compression ratio raises the temperature at which stuff happens in a diesel engine.
2)Clatter - The clattering noise of a diesel engine has nothing to do with detonation. It's the noise of the fuel injection system. Typically, hydraulic pressure of the fuel from the pump forces the injector open at the right time in the cycle and this action makes a pronounced click.
3)Burn - diesel engines take in the same amount of air on each cycle and injects a variable amount of fuel into the heated air according to the load. The injection pump controls the amount of fuel by the length of its stroke.
4)Gears - people who drive diesel care about efficiency and more gears helps improve acceleration and efficiency at cruising speed. A diesel engine has a wider range of torque v rpm than gasoline engines simply because of the higher compression ratios and the longer power strokes. Further, a gasoline engine may red-line at 4000 rpm while a diesel engine may red-line at 3000 rpm. High rpm is a great waste of energy in most cases as the viscous forces in the cylinder/lubricants and gas-flows increase as the square of the velocity. The slowest diesel engines are on ships and may exceed 50% efficiency.
Efficiency of diesel is not just about consumption of fuel and work done. Diesel engines last about twice as long as a gasoline engine, saving fuel, manufacturing costs, and many other energy consumptions around the planet. TFA should have mentioned that the NOx problem exists in all engines but is worse in diesel engines because of the higher temperatures. Many manufacturers inject urea into the exhaust to decompose the NOx. VW opted to cheat on tests instead. They still make fine cars and I would not hesitate to buy a diesel Jetta or wagon. They manufacture a light truck in Asia/Pacific which I would like to have: efficient, geared for efficiency rather than pulling tree stumps... The real problem here is the bad rep of diesel engines. This situation will not help that and the world will continue burning more fuel as gasoline instead of diesel as a result.
The right way to use a diesel engine in a car is as a hybrid. These ~2L diesels can be run at optimal efficiency instead of being chained by gears to the wheels. They would perform better in city and highway driving.
Interesting comment and clearly made points BUT 1 fact you should have checked...
I've not seen a petrol engine that stops at 4000 rpm in the last 15 years, most petrols happily rev to 6/7000 and I've seen some that hit 8-9000... And most are at their highest torque/power at the top end as well...
"most are at their highest torque/power at the top end as well"
This is always the case in petrol engines, hence why race engines have tiny cylinders and stupidly high max rpms. (Back in the 1950s Ducati was making V8 500cc motorbikes and in the 1960s Honda had 4 cylinder 50cc ones. I'd love to have either as a collectors' item.)
Internal friction losses go up with the cube+ of piston velocity, just as rolling air friction does. There's always a tradeoff.
> Back in the 1950s Ducati was making V8 500cc motorbikes
That was Moto Guzzi.
From the article:
"to get that high compression ratio, the diesel engine needs a longer stroke"
There is no relationship between stroke and compression ratio. It is simply the ratio between the volume swept by the piston and that of the combustion chamber.
"the higher density of diesel is the reason there are very few diesel aeroplanes"
I would have thought that the additional weight (required to contain the higher pressures) was more of a factor.
-A.
Another one:
"But charge a Tesla with electricity from a coal burning plant and it becomes a fossil-powered car and just as mucky"
This is too simplistic.
Firstly, unlike a fossil-powered car, a coal burning power plant doesn't pump its emissions directly into the faces of children in crowded High Streets and city centres.
Secondly, because a power station is not a mobile vehicle, it is free to use any emissions cleaning equipment available without having to consider the weight of that kit.
I have a modern pure petrol care which is giving me near diesel MPG and huge lumps of torque from low RPM thanks to a turbo. I can only think that adding a hybrid electric system to help with the pulling away from stopped in traffic etc and to give a little push up hills would make it better than diesel. So there is no case for diesel anymore.
@werdsmith you have an upvote for pointing out the difference between burning the fossil fuel in a car and in a power station, however I want to note that there are good reasons for a diesel to be very clean and efficient in hybrids - i.e. under constant load and RPM, not geared directly to wheels. Where petrol engines benefit (from running at the optimal conditions all the time), diesel ones would too.
"Those who actually care about saving fuel and resources - and perhaps about helping to end the evil of economic growth - might instead consider buying a secondhand VW Polo Bluemotion or one of the various similar cars offered by rival manufacturers a few years back.... though to be sure using diesel."
- editorial note Sept. 2014
Your editor's advice from the end of the Jags to riches article on fuel efficiency.
You give the same advice now and it makes perfect sense too. Toyota managed to shrug off a 10 million car recall after a Lean Quality Control disaster, in less than 5 years.
Regardless of manufacturers' hype, we all know that we never get from our cars the mileage they are claimed to achieve.
The thing is that up until perhaps the mid 2000s, I did get the mileage claimed. I was able to achieve figures perhaps 10% better than those claimed with just a little effort. A side effect was (is) reduced tyre and brake wear - for some years in the early 2000s my dad and we had the same model car at the same age, though his was petrol and ours Diesel. We changed our front tyres literally half as often as he did, and the brake components likewise. We had been expecting the Diesel car to be harder.
We still have a 2006 Diesel Kangoo. It now has 128,000 miles on the clock and achieves between 55 and 60mpg regularly with a journey mix that is probably 80% "short" (under 5 miles) journeys. I used to commute in this vehicle, 45 miles each way, mostly motorway and in the last summer before I "retired" it to the school run, it did three tanks in a row, each one well over 70mpg. Its official figures were low to mid 60mpg from memory.
The car I use now (a 2011 model) has official motorway figures of (IIRC) 72mpg yet I struggle to get it much over 65mpg.
diesel fuel should cost 11 or 12 per cent more than gasoline, because it contains that much more energy and that much more carbon.
But Diesel has (since the 1990s anyway) always been more expensive than petrol. Perhaps not 12% but often 5 to 8%. The current situation where they are about the same price (UK) is unusual and I don't expect it to last. We have bought Diesel cars for the last 10+ years because even with the price difference and the higher up front cost, the economics made sense.
We must not forget CO2 emissions. NOx and CO2 are two completely different things and have utterly different reasons for wanting to reduce them. We must not concentrate on one and ignore the other.
It is only recently that hyper efficient petrol engines have started showing. At the moment they seem to be confined to very small capacity, high revving, highly turbocharged units that must be utterly tiresome on the motorway.
I would love to buy an electric car for commuting and power it with "green" electricity, but apart from the Tesla cars - which are way, way out of my reach - not one of them could guarantee to do my 90-mile commute. Yes they all claim 100+ mile range (I think the Nissan Leaf claims 120 miles at the moment) but when you start asking about the range at motorway speeds, in the winter, with the wipers, heaters and lights on then salespeople get very evasive and manufacturer websites are completely silent. I'm pretty certain one of them could get me to work but I'm just as certain it couldn't get me home again without recharging, and although we do have a charging point at work, I could hardly hog it, and what if someone else needs it?
On top of that we have relatives that live 150-ish miles away. We visit them several times a year, but turning that 3-hour journey into a 2-day journey, plus hotel costs, just doesn't work.
The alternative is to buy an electric car for the school run, but that would mean I'd have be commuting in the large family car we'd need to buy in order to do the holiday trips, which wouldn't be at all efficient.
I'm sticking with Diesel for now.
M.
Mag offered "...hyper efficient petrol engines....at the moment they seem to be confined to very small capacity, high revving, highly turbocharged units..."
They're still working on the 'hyper efficient' 6 ¾ L motors. They'll be out next year. Until then, you'll have to make do with the small ones.
/sarcasm
Re: Jeffy.
It's all very well being "sarcastic" but while I'm sure a Fiat Twin Air works very nicely in a Fiat 500 driven around town, there are two particular circumstances where it doesn't seem like the ideal, nor even the current best, solution:
- stick a Twin Air in a large family car and see how it copes
- nip 200 miles up the motorway and see how your ears cope
M
I easily get the claimed mileage, and better on my new efficient petrol car.
Reduced tyre wear is not a benefit though, as it is necessary to carry energy through corners, can result in some higher than normal corner speeds and increased tyre edge wear.
There was so much garbage written in this article, that it's apparent that the writer has no idea how (or why) a diesel engine works. The diesel engine and the petrol engine work by two entirely different concepts . That for the petrol engine is combustion at constant volume, that of the diesel combustion at constant pressure. In the petrol engine the fuel and air are compressed until ignited by the spark. The gas/air mixture burns in a flash. The pressure rises instantly and provides the driving force. In the diesel, the air alone is compressed . At the end of compression, the fuel is sprayed in over a period of time, so the pressure remains the same, since the piston is descending on the power stroke. The Pressure/Volume (PV) diagram for the diesel is nearer the ideal (The Carnot Cycle, which indicates the ultimate efficiency that may be obtained) than that of the petrol. In practise, the distinction is slightly blurred, but the distinction is still appropriate. Oddly the diesel as invented by Herr Diesel is not a diesel engine in that it is not combustion at constant volume, but, like the petrol engine is combustion at constant volume. In fact the only diesel engines still in use are the engines made for model aircraft, and as far as I know the last commercial true diesel engine was the Vincent Firefly, a cycle motor made in the mid fifties by the Vincent Motorcycle Company during the craze for motor assisted bicycles. It should be noted that Herr Diesel was NOT the inventor of the Diesel Engine that bears his name. The true diesel engine was invented by gentleman of the name Ackroyd-Stuart. His engine was being made and sold by Hornsby and Company of Lincoln, two years before Herr Diesel built his engine. It is this engine on which the modern diesel is based.
In this debacle, my sympathies lie entirely with Volks Wagen and other car manufactures. . Governments issue directives. The directives do not have to based on logic, or indeed have to be obtainable under the laws of Thermodynamics. No doubt the car manufactures argued long and hard to convince the authorities otherwise/ To no avail I've a sneaking suspicion that VW have done nothing unlawful. No doubt their lawyers and engineers have long laboured to create a test which adheres tightly to the provisions of the statute. Much like Google, Apple, Starbucks, etc have laboured long to establish a financial regime which avoids paying taxes, entirely within the legal requirements. The article writer did make one point which seems to have been missed by most other commentators. The US has no diesel powered car manufacture. Every diesel powered car imported to the US is one car not manufactured by the US car industry. I'm sure that their lawyers and engineers laboured long and hard to formulate rules which would effectively exclude the VW from the US
I'm not sure I follow you. Petrol certainly does not ignite all at once, and the pressure is not instant (at least within timescales of the piston moving). And direct injection petrol engines can (and do) vary how the fuel is injected, no doubt in the same way as diesel engines.
The thing to remember with both petrol and diesel engines is that the technology has changed a very great deal in the last couple of decades in both cases.
Diesels have changed from indirect injection using mechanical injectors to direct injection using piezoelectric transducers to modulate how much and when the fuel is injected; modern diesels also use variable vane turbochargers. The net effect is to spread out the torque and power curves, so that diesels are efficient and powerful at a wider range of speeds.
Petrol has if anything undergone an even greater series of changes. Old-style petrol engines used carburettors to produce a petrol-air vapour which was then sucked into the engine. This vapour had to be sufficiently concentrated to ignite from a spark (hence the choke on earlier designs, to enrich the mixture when the engine was cold). This changed to injection into the intake system, and then to the modern, direct injection systems.
These inject petrol directly into the cylinder, but vary the mix so that there is a blob of richer mixture next to the spark plug, and leaner, less rich mixture elsewhere. Combined with a turbo this makes these direct injection engines very, very fuel-efficient indeed.
Toyota hybrid engines have another trick: they are not Otto-cycle engines but are Atkinson cycle engines, which means that more power is gotten out of the petrol combustion cycle, at the expense of somewhat reduced power and torque.
Jaguar recently went one better with a prototype gas turbine engine, which used gas turbines to generate power very efficiently to drive electric wheel motors, with a battery pack in between to smooth the power flow. This works and indeed a US truck company is selling LPG-fuelled gas turbine electric transmission replacement systems, but the problem here is the high cost of the gas turbine engines, which are uneconomic for passenger cars.
"the problem here is the high cost of the gas turbine engines, which are uneconomic for passenger cars."
The engines themselves aren't expensive over their lifespan - until you cook one through bad starting procedure or poor maintenance. Automotive use demands extreme tolerance to operator abuse.
Turbines aren't as efficient as piston engines in most cases (especially turboshafts(*)) but they pack a lot of HP in a very small, lightweight space. That's great for aircraft and not such a big deal for cars.
(*) Power generation turboshafts make up the efficiency loss by putting a steam boiler plant on the end, driven by the hot exhaust. It's kind of hard to do that in a car.
Over 40mpg from a 30 year old Jag is not even remotely possible.
If you took the trouble to read the article linked you would realise that the author did a lot of work to make his Jag that efficient, but that he absolutely did do it.
It was certainly worthwhile from a "let's find out" point of view, but whether it was financially worthwhile is debatable ;-)
M.
> "The apparent low running cost of a diesel vehicle that you would determine by reading the advertising in a magazine is a complete myth compounded from three distortions"
Hmm ... I have an old (2004) 1.9TDI [100hp], which has a published MPG (combined) rating of 54mpg. My commute looks somewhat like the combined test, and I get an overall consumption of 53.8mpg over the last 30,000 miles [typically around 58mpg in summer and 49mpg in winter], based on "brim-to-brim" calculation (i.e. using the odometer reading and the amount of fuel put in), rather than the in-built computer.
As a courtesy car, I recently had the "new" version of my car, with a 105hp 1.2TSI engine for a week. The published combined MPG for this was 59mpg, yet I saw ~38mpg in the week I had it (it was basically used for commuting, so was exposed to the same conditions as my car, if not better, as it was the summer and traffic was light) ... some of this may be due to being a tighter, newer engine, but this is a pretty sizeable difference.
(For what it's worth, I would've gone with a petrol engine when I got my car, but the diesel option was far better than the available petrols in terms of driveability and lack of known issues)
Haven't seen anyone post the correct fact anywhere, but a number of flat-out WRONG posts.
Jet fuel is not "the same as" diesel fuel. Jet-A is essentially kerosene (terminology in the US, Canada, India, Australia, and New Zealand), which is called paraffin in the UK, Southeast Asia, East Africa, and South Africa. Of course Jet-A has strict specifications not guaranteed to be met by common kerosene.
Diesel motor fuel for road use is either #1 or #2. #1 is essentially kerosene, and #2 is the well-known substance most people recognize as "diesel fuel". There is also a heavier cut used by ships at sea and by railway locomotives, but that is off-topic when discussing road use.
Most pump diesel fuel is #2, except that in regions which get cold weather in the winter, it is cut with #1 during the winter time in order to most easily reduce the problem of cold-gelling.
Jet engines can happily burn either kind of diesel fuel, as well as a wide variety of other liquid fuels, but are not certified to do so reliably or long-term.
Historically, diesel engines have been able to burn Jet-A very well. That is essentially what they are burning when they use #1 diesel fuel. In fact, with the diesel technology as it existed up to the 1980s, savvy owners knew that in a pinch you could fuel up with gasoline, cut 5-10% with motor oil in order to afford viscosity and lubricative properties more appropriate to the diesel injection pump and injectors. The vastly higher injection pressure which later came about for emission reasons made this a poor idea, and common-rail pretty much drove a nail in the practice. You can still use Jet-A; in fact aircraft diesels are only certified for it; but to use it long-term it would be best to have an injection system adapted and tested for it, as aircraft diesels are.
I'll carry on with my 2005 Panda. 1.3 diesel. Official mpg of 65.7. My ten year old, 100k miles vehicle does between 62 and 74mpg depending on temperature, length of run and loading. "On the road tests" are rubbish as there's no consistency for comparative purposes. Defeating the rolling road test should be illegal (if it isn't) as it's basically making a fraudulent claim.
Sulphur first, particulates next, NOx after that ... what's next in the 'I hate diesels' campaign?
Just for reference, Norwich has made huge areas 'pedestrian and public service vehicles' only. One of the largest ones was named on the NOx study as having excess NOx ... it doesn't appear that anyone's questioning the figures, what the underlying cause is, or what they actually mean, they're just blaming the easiest target - diesel cars - which in Norwich's case is probably incorrect ...
if the goal is to encourage engine technologies that are fuel efficient and low in emissions, then surely a level playing field is to be desired. Thus, diesel fuel should cost 11 or 12 per cent more than gasoline, because it contains that much more energy and that much more carbon"
This is only true if you accept that "diesel" is only a product of fossil oil. Which it isn't.
The reason I bought a 20-year old Toyota Hilux, is that it happily runs on converted vegetable oil.
The benefits of this are multiple:
- The engine runs cooler, and bio fuel has self lubricating properties reducing wear and tear. WIN.
- Low NOx emissions. WIN.
- Low particulate emissions. WIN.
- The CO2 output comes from within the carbon cycle, this doesn't add new carbon to the atmosphere. WIN.
- Recycling vegetable oil means it doesn't go into landfill. WIN.
The two FAILs I can see currently:
- The Government refuses to promote biodiesel as a fuel, so you still need to go and seek it out if you want to run your vehicle on alternative fuel.
- Current spec vehicles have been engineered to get the absolute maximum economy out of fossil diesel, so things like the injectors may not play nicely with the different viscosity fuel.
"it happily runs on converted vegetable oil."
It's an even bigger WIN if you modify the engine system slightly (fuel line heaters) so that it runs on unmodified vegetable fuel:
No noxious byproducts from the conversion
You don't lose 50% of the available energy in the oil to the conversion process.
Re: "The two FAILs I can see currently:"
There is a third, that you probably can't see due to you only seeing trees and not the wood: we can't produce sufficient biodiesel and still feed the world...
So whilst we should encourage some to take advantage of biodiesel and other interesting fuels, they are not mass market fuels.
There may well be concrete advantages to running your diesel engine on vegetable oil, but I fail to see how low NOx and particulate emmissions can be among them. The NOx comes from subjecting the N and O *from the air* to high combustion temperature and sub-stoichiometric fuel quantity. The particulates are just soot, which you get from burning anything that's got carbon in it.
I'd prefer to be proved wrong than downvoted, by the way.
-A.
Gasoline and diesel are both hydrocarbons, and if burned with pure oxygen would produce water and carbon dioxide. But burned in air, which contains a lot of nitrogen, some other compounds are produced as well, especially as the temperature rises. Indeed, it will in a diesel running at low power, where a tiny amount of fuel finds a vast amount of oxygen and burns like crazy. This results in high temperatures and NOx – the x being the classic variable to denote that various numbers of oxygen molecules can be bound to one of nitrogen.
Then why not just remove the nitrogen from the air?
There are a number of ways of doing this for medical and industrial applications. Surely one or more of these methods could be applied to diesel engines.
Yes, using a very large superconducting magnet works.
Slight snag here is that all the ones I've seen with useful field densities (ie in the .5 Tesla range) require liquid nitrogen or more usually liquid helium to stay cold enough to superconduct.
Ironically the Chinese buying up all the neodymium recently might have to do with wind turbines and emissions control systems, they are heavily into renewable energy due to the smog issue.
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