Discussion > Diesel Eco-good or Eco bad ? ... from Unthreaded
I know very little about the pros and cons of diesel/petrol/ethanol/lpg as fuel for the internal combustion engine. Personal experience suggests that diesel has the most obvious emissions (in all meanings of the word) and LPG the least. Poitiers has bendy buses which use LPG and Limoges uses trolley buses; in both cities there are lower levels of detectable to a human air pollution. However this doesn't mean that there aren't nasty emissions. Petrol certainly has harmful components.
Hopefully this will be like the Thorium discussion where some knowledgeable people post useful (or even people posting red herrings) and I learn something.
Living in rural Limousin, in winter, the most detectable air pollution comes from domestic wood burners.
SandyS
Seems to me the history is
- 1. diesel good , more efficient than petrol
- 2. petrol gets catalytic converters, so petrol is clean wheaers diesel spurts the kind of particulates that could cause cancers eventually, so diesel bad
- 3. so UK gov increases diesel price to favour petrol
- 4. diesel good , Diesel can easily fueled by biofuel
- 4. the alledged recent improvements to diesl ..largely fix the particulate problem ..so diesel good again ?
..."I have beeen wrong before"
stewgreen
Ignoring the particulate emissions it used to make sense to run a diesel car, I had a A reg Audi 100 that returned 50mpg, diesel was cheaper than petrol, the engine was home repairable and petrol engines no where near as efficient.
Today, petrol is cheaper than diesel, petrol cars are closer in efficiency to diesel, diesel cars have all manner of extras added to help reduce particulates and improve vibration levels so are no longer serviceable at home and these extra features like dual mass flywheels and exhaust filters are prone to failure and expensive to buy replacements.
Nissan had a major problem with the Quashai, advertised are for the Urban jungle they were bought in diesel version by city dwellers, trouble was to regenerate the exhaust filter you need a regular high speed run. In a city this takes some doing so filters were failing regularly, cue Nissan embarrassment and salesmen having to ask potential customers what type of driving they intended to undertake.
So unless you do a huge mileage, for the moment stick with petrol.
Breath of Fresh Air
The process will be familiar to most here. In order to facilitate banning the hated private car, they went all out to find problems which could be attributed to petrol engine emissions. This meant that diesels became popular, so they started looking for something else, and decided it was to be particulates. It all helps their case for trains and trams, which some of them actually describe as "zero emission" (because "Coal powered" doesn't sound very green).
As car use has risen along with all sorts of other things as society has advanced, it is a simple matter to correlate it with any health issue which can be made to appear to increase over a similar timescale and claim causation as a result. There is plenty of the usual pal reviewed dross from third rate academics on the subject. It's where I first saw the fiddling techniques which would later become so familiar in CAGW, like conclusions which aren't supported by the experimental data but which are put in anyway on the basis that nobody will read or understand the data.
The initial attempt focussed on "asthma clusters" until it was pointed out that these clusters appeared randomly around the country including places like Orkney. This is because they are a statistical anomaly caused by the effects of random variation on insignificant sample sizes.
In another familiar situation, they are now setting arbitrary particulate limits based on roadside sampling. As these sampling stations appearing at our roadsides recently are a new thing, there is of course no comparable historical data to be able to say whether or not there is a problem. The stations are also carefully placed at traffic lights, on uphill urban one way streets etc. to produce the worst possible results. Very Climate Science.
NW
As I said earlier I am no expert on the subject.
When I was a resident in the UK I used to like browsing through the Daily Telegraph Motoring section in the Saturday edition. The Honest John page which answered readers queries on the maintenance and reliability was quite interesting and often useful. When I wa in the market for a replacement car Honest John's opinion was that in general modern petrol cars were more reliable than modern diesels (Euro4 & Euro5 standards).. I think apart from all the additional sensors there were mechanical elements in modern diesels which led to the economy from greater mpg being out weighed by potential large repair costs. Two particular items were particulate filters becoming clogged and dual mass flywheels becoming early failures. In an older, say 5-6 year old, vehicle repair of either is uneconomic.
When I did a bit of research earlier I found some advice from Honest John on increasing the life of a DM flywheel, this involves skills which are no longer taught and most drivers under 30 won't have heard of.
Don't let the clutch out when you're in gear and the engine is idling – always apply some revs. Also, try to double declutch smoothly up and down the box. That's the advice offered by readers whose DMFs have lasted for 200,000 miles.
Progress being the proverbial one step backwards.
SandyS
If your Diesel car has a DMF you can replace it with an SMF as a lot of minicab drivers do from new. A little rattle on idle with the clutch out but otherwise no difference.
Morph
A couple of questions....
* Do diesel engines (under similar conditions of use in similar cars) last longer than petrol engines?
- My 2.4 litre diesel Volvo 940 has done 270,000 miles, half of it in my ownership, and I think it has never had a cylinder head off. It burns no oil and gives 35 mpg.
- I heard (dunno how true it is) that diesel in cold cylinders acts as a lubricant, so less cylinder wear when the engine is cold.
* In the 1940's (I think) a car would have a decoke every 10,000 miles or less. And would have had several rebores in its lifetime. What changed?
Martin A
A couple of questions....
* Do diesel engines (under similar conditions of use in similar cars) last longer than petrol engines?
Don't know about modern diesel but yes old diesels lasted longer as the major components where strengthened to cope with 23:1 compression ratio, that plus the lower revs extended bearing and piston/bore life.
- My 2.4 litre diesel Volvo 940 has done 270,000 miles, half of it in my ownership, and I think it has never had a cylinder head off. It burns no oil and gives 35 mpg.
- I heard (dunno how true it is) that diesel in cold cylinders acts as a lubricant, so less cylinder wear when the engine is cold.
Diesel is thicker than petrol and closer to oil, you can run an old diesel on filtered but untreated used veg oil as soon as the engine is up to temp and the coolant is used to pre warm the oil to thin it out.
* In the 1940's (I think) a car would have a decoke every 10,000 miles or less. And would have had several rebores in its lifetime. What changed?
New fancy materials which last longer, new machining techniques that allow closer tolernaces introduction of detergent oils and inline 30 micron filters, petrol and diesel additives cleaning combustion chamber.
Breath of Fresh Air
Morph
Presumably there is a highist expense in swapping a DMF flywheel and it can only be done outside warranty. Probably OK for taxi drivers who expect to swap s couple of DMFs whilst clocking up 500k miles not so reasonable for a private motorist who might leave until failure?
Breath of Fresh Air
Isn't the problem with fueling a modern HDI type diesel with petrol that the high pressure fuel pump is made to much tighter tolerances and is terminally damaged?
SandyS
Breath of Fresh Air
Isn't the problem with fueling a modern HDI type diesel with petrol that the high pressure fuel pump is made to much tighter tolerances and is terminally damaged?
The old pumps were also ran the injector fuel pulses driven by a internal cam, they ran at low pressure and can cope with lots of variations of fuel including oil, just as long as its clean.
The newer pumps driving the common rail only supply the pressure which is much higher, the injectors time their injection pulse by receiving an electronic pulse from an ECU. They are not capable of handling a wide range of fuels and suffer when fed out of spec fuel. No idea if they are rebuildable like the old ones.
Breath of Fresh Air
Martin A: * In the 1940's (I think) a car would have a decoke every 10,000 miles or less. And would have had several rebores in its lifetime. What changed?
Fuel quality and octane mostly which gives cleaner burning and more efficient combustion as higher compression ratios can be used.
ssat
(sorry - wrong thread)
Martin A
Regarding Bio-Diesel
I read recently that this fuel was causing engines to get clogged up and need expensive repairs, the problem increasing as the amount of bio additive increases?
Dung
Dunno about bio-diesel, Dung, but you are certainly recommended very strongly not to put the 95 octane stuff with alcohol in it (which is produced from crops as I understand) into your 1950's collector's car if you don't want to seriously bugger up the fuel system.
Martin A
Martin A
Ethanol in Petrol causes problems to more than just 1950s cars. I have found (partially as a result of interest piqued by this discussion) that it can cause to a greater or lesser degree
There is an interesting site here with a very comprehensive list of issues for the E10 fuel.
Water accumulation in fuel tank - ethanol absorbs water from the air (particularly in marine environments if left in tank)
Deposit build up
Loss of power
Rough running
Lower fuel mileage
Corrode internal engine components
Contaminents in fuel system *
Fuel phase separation - cannot be restored
Encourages microbial growth in fuel *
Short shelf life -as short as 90 days
*Possibly in bio-diesel too?
SandyS
The Bio diesel problem is not proven as yet, but the clues are pointing to bio diesel being the cause of fuel starvation due to the filters getting clogged in cold weather.
The Ethanol in petrol problem is not just a problems to 50's engines, it affects all carburettor equipped engines so a brand new lawn mower will suffer, it leaves deposits in the jets especially the small pilot jet which can only be cleaned out by a drill, carb cleaner will not shift it, unitil the jets are cleaned it won't start. It has also affected some modern plastic petrol tanks eg on Ducati's and KTM's requiring new materials, the ethanol attracts water which then collects in the bottom of the tank which if steel starts rusting, it also attacks the resin in glass fibre tanks for boats and motorcycles. All this has been communicated to the powers that be but they only want more ethanol eg E10 is next.
Breath of Fresh Air
BoFA, that is what I have occasionally read about biodiesel, that the major problems arise from the physics and chemistry before it reaches the combustion chamber.
A few days ago I took a look at the chemistry of a process converting "vegetable oils" to "biodiesel". As far as I could see it only converted long-chain fatty acid methyl esters to their respective ethyl esters. In my experience this would increase the liquid temperature range (methyl esters tend to crystallise more readily) and reduce the rates of chemical and biochemical spoilage (methyl esters tend to react more readily, primarily with water in this case.) It would probably also improve miscibility with other (fossil fuel) hydrocarbons.
michael hart
"electric cars haven't really caught on why is that ?" in the show BBC R5 Joy Of Tech last 3 mins has the Tesla Europe boss plugging their new model Tesla-S for the UK
.. it's got a range of 350 miles and the journalist did get 200 miles,
... they then mention even with the subsidies it costs £50,000 !
stewgreen
Michael Hart; with respect, the Biodiesel production process is not as you describe. I know a little about it from a brief involvement in a biodiesel project about 5 years ago.
The basic process reacts methanol with tri-glycerides using a catalyst to produce fatty acid methyl-esters (FAME) and glycerine. The FAME is then cleaned, refined, etc and suitable additives included to produce Biodiesel.
Biodiesel properties vary, depending on the feedstock which can be anything from used cooking oil or tallow through to a multiplicity of vegetable oils. For example, rapeseed-derived biodiesel has better cold-flow characteristics than fuel produced from palm oil which is, in turn, better than that produced from tallow.
mikeh
stewgreen
in the UK all of this is the fault of Millibrain and Mendleson ^.^
They gave a shed load of our money to support extra research by the motor industry into electric and hybrid cars. Without our money they would have had no reason to do that research (and they still can not make the bloody things work hehe)
Dung
It was just one that I looked up, MikeH. They only thing they described was a trans-esterification process to form eethyl esters, so I tried to draw some conclusions from that...incomplete I guess...
michael hart
Michael H,
I found I have some write-ups in my old files from companies like Lurgi and Ballestra. If you want more info, their websites might be useful.
One of them included a clear equation but it won't copy across. The text is below.
An interesting side-issue is that this process produces loads of glycerine - approx 10% of the biodiesel output. One of the challenges is to find new uses for glycerine as the historic pharma market is very small.
It is not widely known that glycerine is the basis for many of the various gels, creams, lotions, etc which sell for silly prices to the chatterati. Wonder how they would react if they knew that their mega-price wrinkle cream was mostly made up of the by-product of an industrial chemical process....and that the feedstock can be animal tallow, grease scraped from sewers, old cooking oil or that arch-baddy, palm oil??
5.1 Biodiesel Chemistry
Biodiesel is a mixture of methyl esters of long chain fatty acids like lauric, palmitic, stearic, oleic, and so on. It is produced by the transesterification of animal fats and vegetable oils – all of which belong to a group of organic esters called triglycerides. Typical examples are rape / canola oil, soyabean oil, sunflower oil, palm oil and its derivatives, etc. from vegetable sources, beef and sheep tallow and poultry oil from animal sources, and also from used cooking oil. The chemistry is basically the same irrespective of the feedstock.
An example is Oleic acid, which has 18 carbon atoms and one double bond:
CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH=CH-CH2-CH2-CH2-CH2-CH2-CH2-CH2-COOH
or more simply: CH3-(CH2)7CH=CH-(CH2)7COOH
The abbreviation C(18:1) is also often used.
Typically, 1000 kg of dried degummed and deacidified rape seed oil will produce approximately 1000 kg of biodiesel (RME) plus 128 kg of crude glycerin, which in turn can yield some 93 kg of pharmaceutical grade plus 5 kg of technical grade glycerin. This will require 96 kg of methanol and approximately 5 kg of catalyst (as 100% Na-Methylate).
mikeh
Diesel vs petrol radio 4 now : Renewable energy and the cost of diesel Friday 16 May 2014
"Peter White looks at
1. how far more solar farms and wind turbines have been built than the government expected *.
0:33 And why, unlike much of mainland Europe, diesel costs more than petrol in the UK #.
... And efforts to protect bowling greens from the developer."
* Corruption or usual DECC incompetence I expect
# We have a thread for discussion Diesel Eco-good or Eco bad ?
May 16, 2014 at 12:36 PM | Registered Commenterstewgreen
So what reason was given for diesel being more expensive than petrol in UK?
Martin A
Those You and yours stories
The gov cuts (large scale) solar subsidy story :
last year cost large scale renewables subsidies was £33 now its £40 to each bill payer
Homemade renewables energy subsidy cost moved from £8 to £10
So the gov has put the brakes on subsides before the rise gets out of control
Prof said they can't predict how much future subsidy costs will be
"by 2020 bills could be lower due to renewables or they maybe adding 10%"
..I think we could compare a country with no renewables to one with green politics and find bills are 50% higher not just 10%..see germany now never mind in 2020
stewgreen
a continuation from unthreaded
- "The deadly diesel deception: We were bullied into buying diesel cars to help fight global warming. Now experts say this ‘green’ fuel is killing thousands of us
‘In hindsight the switch to diesel was a mistake,’ he, [Martin Williams, professor of air quality at King's College London,] says. ‘In the past 20 years we’ve had far more toxic emissions from cars than we should have done.’
How did such a dirty, noisy and dangerous technology fool so many experts?
The reason appears to be that car makers, governments and environmental groups were so wrapped up in the mania for reducing carbon dioxide emissions that their ‘experts’ managed to overlook the other highly toxic pollutants that diesel engines produce.”
Daily Mail
May 1, 2014 at 12:34 PM | Registered Commenter Robert Christopher