Dieselgate, after the dust has settled

I have owned and driven diesel cars and vans since I passed my driving test, bar one petrol car when I first passed. I have always been a devotee of diesel cars and diesel engines in general, in my opinion for reliability and long distance fuel efficiency they cannot be beaten.

Even with the development of newer more efficient petrol engines, they are unable to compete with diesel engines for fuel efficiency, pure pulling power and reliability. That is why diesel engines still power the modern economy, diesel engines are used to power the machinery which produces the food we eat and drive the vehicles which transports the goods we buy.

So, it was with great surprise and disappointment that I learned (admittedly this was some years ago) that some car manufacturers were cheating the system and were allegedly building diesel powered vehicles that emitted more dangerous gasses than were allowed under US and EU law. This news has since gone on to have a huge knock-on effect to vehicle manufacturers, even those for which no allegations were leveled against them.

I believe however that news reports on the story at the time were confusing and didn't really explain what particular legislation the engines were falling foul of, nor in my opinion did the media fully explain which emissions were being released at levels above those allowed.

To be Frank I think the media and government's subsequent over-reaction lead to the collapse of the market in diesel engines, a fact which has has been particularly harmful to the UK vehicle manufacturing industry.

Jaguar Land Rover in particular has paid a heavy price for the fallout from diesel-gate, being that diesel powered vehicles make up a large proportion of those sold by the company. Diesel engines after all being most suited to large vehicles such as Land-Rover 4x4s and sports utility vehicles.

Environmentalists will probably be chomping at the bit to explain why it was the vehicle manufacturers fault that diesel-gate happened at all, but let me explain why I think the Governments' move to being anti-diesel was and is an overreaction.

I should start by saying that I am in no way defending those manufacturers who cheated the system, what they did was outrageous and unacceptable but I do think that the media and government has a lot to answer for in its response.

If I'm perfectly honest I don't know full details of how manufacturers cheated the system, but as I understand it the under certain circumstances on-board computers of cars fitted with certain diesel engines were programmed to know when the vehicle was under test conditions (or programmed prior to test), the engine management system would then use various means to reduce the amount of Nitrogen Oxides (NOx) the engine produced, therefore allowing the vehicle to pass US and EU emissions tests.

The result being that some diesel cars were emitting greater amounts of NOx than legally permitted. Therefore breaking US and EU law and deceiving consumers into believing that the vehicles were more environmentally friendly than in reality.

Now, it is important to understand the difference between NOx, CO2 and the impact each has on the environment. CO2 is an invisible and odorless greenhouse gas emitted by all internal combustion engines, for which there is overwhelming evidence to suggest it is one of the major factors in global warming. NOx on the other hand has a more localised effect on the environment and people, "The main effect of breathing in raised levels of nitrogen dioxide is the increased likelihood of respiratory problems. Nitrogen dioxide inflames the lining of the lungs, and it can reduce immunity to lung infections. This can cause problems such as wheezing, coughing, colds, flu and bronchitis." [1]

Therefore NOx emissions are a serious threat to people's health and the amount of NOx that vehicles can produce is tightly controlled, hence why US and EU emissions standards have been steadily tightened since 1991 when, in Europe the Euro I standards for passenger and light vehicles were first introduced. In 2014 Euro 6 stands came into force which limited the amount of NOx that was permitted to be released to 0.080g of NOx per km.

So when the diesel-gate story broke and the media began to refer to "emissions", the first thought the public had was that diesel are much worse for the environment than manufacturers and indeed governments had been claiming for decades. Whilst it is entirely true to say that some diesel vehicles were more efficient than their modern petrol equivalents. This means that diesel vehicles still produce less C02 per km when compared with similar petrol vehicles in certain circumstances.

Diesel-gate Paradox

Before I go on to the way in which manufactures can and do limit NOx, it is important to realise that there is there is some what of a paradox which played a part in the current situation. Manufactures have strived to make engines as efficient as possible since the invention of the diesel engines back in 1890 by Rudolf Diesel.

Technologies such as injection, later direct injection and turbo charging have lead to diesel engines which convert as much as 45% of the fuel into mechanical energy, compared with petrol engines which are broadly only 30% efficient.

However in order to increase efficiency the temperature of the burn must be increased. With increasing temperatures and pressures comes an unwanted byproduct, NOx gases. So when the EU and US began to clamp down the amounts of NOx that can be emitted by motor vehicles manufactures began to look at ways in which to reduce the emissions.

Exhaust gas re-circulation 

Paradoxically one method was to reduce the temperate at which the diesel burnt. The method which the vast majority of manufactures eventually settled on was exhaust gas re-circulation (EGR). EGR is a method of reducing the temperature within the cylinder and therefore the amount of NOx emitted. An EGR valve works by letting a small amount of exhaust gases back into the cylinders, this has the effect of reducing the temperature of the burn within the cylinder, thus reducing the amount of NOx generated.

EGR is a relatively inexpensive way in which to reduce NOx, however it does have its drawbacks, mainly in that by reducing the combustion temperature the efficiency of the engine is reduced. Also EGR valves must open and close at very specific points, they should not for instance open when the engine is cold. However EGR valves can become clogged with soot from the exhaust gas mixture and therefore remain jammed open during periods when they are supposed to be closed.

Selective catalytic reduction

There is another way to reduce NOx however, and it is a method which is already widely used within heavy goods vehicles and agricultural machinery. The alternative is to inject what is know as diesel exhaust fluid DEF (32.5% urea and 67.5% deionized water) [3] into the exhaust stream, the subsequent chemical reaction converts the NOx gases into gaseous nitrogen and water. People will most likely know the fluid by one of its brand names, Adblue. This is sold at most petrol stations and it poured into a small tank which often has a blue cap.

The process known as selective catalytic reduction (SCR) can reduce NOx emission by up to 90% [4] whilst allowing the engine to burn the fuel at the optimal temperature, therefore it would seem to tick all the right boxes, it reduces NOx whilst allowing diesel engines to operate at high temperatures and therefore more efficiently.

However SCR systems are more complicated and therefore upfront costs are greater, also drivers are required to ensure that the system is topped up with DEF without which the system does not work. This isn't an issue so much with HGV drivers and farm machinery operators who are typically more accustomed to regular vehicle maintenance and checks, also the cost of larger engines is enough to negate the upfront cost of the SCR system. This may be why, whilst adblue has been on the market for a number of years, up to now only a small number of vehicle manufactures have been willing to fit SCR systems to personal vehicles and small commercial vehicles.

Conclusion 

After all that, in conclusion given that there are practical means of reducing NOx emissions to "safe" levels I believe that governments have been rash in their decisions to begin clamping down on diesel engines. Even if governments reconsider their decisions as SCR system become more common, the looming potential threat that all diesel vehicles could be banned from city centres or urban environments is enough in my opinion to have irrevocably damaged the market for diesel vehicles, even though there may still be many benefits of driving diesel powered vehicles for certain types of drivers. 

Final thought

I do think that diesel engines are most likely unsuitable for people who only drive around town and hardly every venture out onto the motorway, not least because the benefits of greater economy will not be felt, but also because as well as EGR and SCR, diesel vehicles also employ diesel particulate filters (DPF) which reduce heavy particulates (soot). 

The filters work in urban environments when the engine is under reduced loads to capture the particulate matter. Said filters are then designed to "regenerate" in a process which burns off the soot in order to clean the filter, however this process usually only occurs at high speeds or when the engine is under sustained heavy load, therefore in theory burning off accumulated soot away from urban environments. Hence why I believe that diesel powered vehicles are suitable for motorists who do a large number of miles and use motorways often.

[1] http://www.environment.gov.au/protection/publications/factsheet-nitrogen-dioxide-no2

[2] https://en.m.wikipedia.org/wiki/European_emission_standards

[3] https://en.wikipedia.org/wiki/Diesel_exhaust#Remedies

[4] https://www.prnewswire.com/news-releases/clean-diesel-what-is-scr-selective-catalytic-reduction-how-does-it-work-----why-is-it-important-300158921.html

The end of Diesel trains?

By Chris Howe


On the 12th of February 2018 the Minister for transport Jo Johnson MP announced that he "would like to see us take all diesel-only trains off the track by 2040". This being the same deadline set by the government to ban the sale of all petrol and diesel cars. The announcement got little press attention considering the Minster had set such an ambitious target, which if it was to be achieved would require a huge investment by the government.

The devil though is in the detail, two little words which water down the announcement from one which could have involved large-scale electrification being put back on the table, to one which simply pays lip service to the environmental debate. The two words being "Diesel-only", very carefully chosen as not to undermine the £5bn investment that is being made in a fleet of new trains to replace the aging HST fleet. Why? Because the new trains which are only now coming into service and are expected to be in service for 30 or 40 years have diesel engines fitted to provide power on non-electrified routes.

A soon to be replaced HST passes Honeybourne station. This route does not fall within the GWML electrification programme, therefore any new trains serving on this route will require diesel power for the foreseeable future. 

If the 2040 deadline had been for all diesel-powered trains it would mean removing the engines from a fleet of trains which by that time will be little over 20 years old, no big deal however because they were designed with this in mind, as/when electrification was extended. BUT, this would mean the government would only have 22 years to fund, plan and complete the electrification of many hundreds of miles more of railway than already planned.

22 years does seem a long time, however Just to remove the engines from the new class 800s and 802s which will be operated by Great Western Railways would mean extending the wires from Cardiff to Swansea, Oxford to Worcester and Bath to Penzance. This alone may be achievable, but it is hard to see how any other routes such as Midland Mainline and TransPennine could be electrified with the time allowed, given that the GWML electrification programme, is billions of pounds over budget, behind schedule and has been de-scoped with electrification between Cardiff and Swansea now cancelled

9 years since GWML electrification was announced and still there's a year to go before trains will be running on electricity only between London and Cardiff, whilst other routes such as Oxford to Didcot Parkway will have to wait a further 2 years. So in all, it will have taken 11 years from go-ahead to completion to electrify 235 miles of railway. Such is the scale of the challenge just to electrify the GWML other schemes have had to be deferred or cancelled altogether.

So we are left with a ban on "diesel-only" trains, this gives a reprieve to bi-mode trains such as the class 800s and others currently on order. But what of the class 195s, yet to enter service are hailed as the much-anticipated replacement for Northern Rail's fleet of loathed Pacers? These new trains will be "diesel-only" and will operate in some cases on lines with no wires for most of their length and for which there are no current plans for wires. By the time we get to 2040 the trains will be little over middle aged and given the cost of rolling stock the owners would surely hope to get 30-35 years out of their investment.

One of the soon to be replaced Pacers sits at Chester station, these trains will be replaced by modern diesel-only DMUs

The 2040 announcement whilst ostensibly sounds like great news for environmentalists and passengers, it could seriously jeopardise investment in new rolling stock in the near future. Who would want to invest in a new fleet of diesel-only trains which may only be in service 20 years or less? The Wales and Border franchise which is soon to be taken over by a new company still has a fleet of 30 Pacers and across the country there are 1000 aging diesel Sprinter units which will have to be replaced within the next 10 years.

Hydrogen fuel cell power is one option being investigated but plans are only now being put in place to test such trains in the UK, so hydrogen-powered trains won't be carrying passengers in the UK for at least 5 to 10 years. This leaves a gap in which time rolling stock owners may choose not to invest in new trains and try to keep trains running which are already well past their best, heck it could mean a few Pacers still being in service well into the late 2020s.

Class 230 "D-Train" being developed could be one answer for the short/medium term, using second-hand aluminium bodies these trains could be pressed into services quickly and provide a return on any investment in well under 20 years. 

I hate to be cynical about the railway but I think setting such a deadline could have a negative impact in the short to medium term, it relies too much on the assumption that unproven technology (at least in the railway sense) such as batteries and/or hydrogen fuel cells will be a viable solution in just a few years time. 

Follow me on Twitter and Facebook - For more information e-mail Blog@EngineeringFocus.co.uk