General Has diesel had its day?

Discussion in 'General Discussion' started by Jonnyjohnson, Sunday 11th Oct, 2015.

  1. Jonnyjohnson Junior Member ☆ ☆ ☆ ☆ ☆

    United Kingdom Jonny East Sussex
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    After having run diesels for over twenty years I have returned to a petrol engined car.
    My reasons for this switch has come about because of the bills I have paid repairing a euro4 engine. Over the last two years and approximately 12000 miles I have had the
    MAF fail, throttle body failure, EGR valve removed and cleaned, and final straw was when the swirl system failed. All these components are fitted to achieve ever decreasing emissions. Each time one of these components failed it put the car into limp mode and involved an expensive visit to main dealer for said repairs.
    Now VW and other manufacturers have been caught out failing to meet emission requirements, and using software tweaks to pass, I personally don't believe these exacting requirements can be achieved without such software or high failure rates of DPF's, regeneration systems etc etc. What say you?
     
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  2. Zebster Expert Advisor ★ ★ ★ ★ ★

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    I've known MAFs, throttle bodies and EGR valves fail on petrol engines (and would assume that swirl valves could fail as well). In fact, on my Omega V6 the EGR valve didn't just fail, it fell apart and began blasting exhaust gases under the bonnet when driving home to North Hants from Chepstow. Taking a car to a main dealer for repairs will always result in massive bills... maybe these things could have simply been cleaned, rather than replaced?

    It's having a DPF that puts me off ever having another diesel.
     
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  3. SpeedyGee Administrator Staff Team

    England Speedy Birmingham
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    If you're not doing the miles then a petrol is the more sensible option.
     
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  4. ArcticFire-Account Closed Banned Getting Started

    Scotland Graham Scotland
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    It's still difficult to produce both power, economy and low emissions without a blower which in itself brings added complications to an engine which I reckon is the main restricting element with petrols. Diesels do have extra problems but I reckon both are on their way out, but diesels will probably go first. Perhaps a little longer in the commercial sector.
     
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  5. exec Premium Member Club Supporter

    United Kingdom London
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    Doesn't it become false economy when you have to spend so much money repairing diesels overriding any fuel cost saves?

    All I ever see and hear about diesel is endless amounts of issues.
     
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  6. Zebster Expert Advisor ★ ★ ★ ★ ★

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    Presumably because owners with reliable diesels tend not to start threads telling everyone? Additionally, there are far more diesel Accords than petrol Accords, plus these diesel models (very popular with fleet buyers) will have far higher average mileages... no wonder forums have more reports of problems with diesel cars!

    In nearly 9 years of ownership I've only had two serious issues (timing chains and a regulating solenoid in the fuel pump) which were both reasonably DIYable and inexpensive. I'm honestly still glad I have a diesel, rather than a petrol model (my other car is petrol, BTW... I'm not anti-petrol!).
     
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  7. chunkymonkey Senior Member ★ ★ ☆ ☆ ☆

    United Kingdom Gary Lincs
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    Not sure how the future will pan out for both to be honest but in my opinion hybrid is not the future either, look at the amount of pollution is caused by actually making lithium batteries in the first place, that and the cost of replacement when they die make hybrids uneconomical too and if they go wrong they are very complex. Diesel and petrol will be around a few years yet IMHO
     
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  8. exec Premium Member Club Supporter

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    I don't mean just in cyber world but in real life too, lots of family, friends and general people I know who have diesels seem to always have problems.
     
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  9. Pottermus Valued Contributor ★ ★ ★ ★ ★

    The biggest problem modern diesel owners have is that they bought the wrong car to start with.

    Fred and Dorris buy a diesel because it's cheaper for them to go to the shops twice a month.
     
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  10. Jonnyjohnson Junior Member ☆ ☆ ☆ ☆ ☆

    United Kingdom Jonny East Sussex
    18
    8
    I had no problems to mention in twenty odd years, but as I said earlier the last two years had been very expensive for repairs. My previous car was a Volvo with the D5 engine, it had only covered 70k miles but became a millstone. This was my second Volvo with the D5, the first giving me no problems up till I sold it with 100k. Previous diesels have been Mercedes, Ford, Peugeot/Citroen and engine problems had been miniscule
     
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  11. Zebster Expert Advisor ★ ★ ★ ★ ★

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    Diesel problems seem scary because most owners haven't got a clue about what all the 'alien technology' (e.g. the bits you don't get on most petrol engines) actually does, how you diagnose it, nor how you fix it.

    Unfortunately this is true of a lot of professional mechanics, as well...
     
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  12. ArcticFire-Account Closed Banned Getting Started

    Scotland Graham Scotland
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    The maintenence costs of hybrids will come down in time as they become more developed, that is if hybrids do take off properly.

    As for the pollution of making the materials and generating electricity at the power plants well that can be done in more remote places and therefore reduce pollution in built up areas and being the narcasistic, selfish earth destroyers that we humans are, this will fit in nicely with our continued global domination and destruction. Win-win for the human.race. Until it's too late of course but by then we will probably be ready to move onto another planet to ruin lol
     
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  13. jimjams Expert Advisor ★ ★ ★ ★ ★

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    possible curved-ball is a petrol engine with the efficiency of a diesel

    i.e. 5-stroke, which has two small high-compression cylinders coupled to one large cylinder which thereby reduces the temperature in the high-compression cylinders (because "work" is extracted as the exhaust gas leaves the high-compression cylinder)



    5-stroke engine

     
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  14. Blizzard Club Member ★ ☆ ☆ ☆ ☆

    Whether or not diesel has had its day, one thing you can guarantee.... HM Government will continue to fleece the end user to the very best of their abilities.
     
  15. FirstHonda Premium Member Club Supporter

    ^^ I remember VW/Audi claiming this when they first launched their TSi / TSFi engines a few years ago. They are almost as efficient as diesel in terms of MPG, but still seem to be higher in terms of C02 emissions.

    I don't think diesel has 'had it' quite yet. IMHO the current scandal will simply mean a short-term focus on the tests and how accurate they are, followed by manufacturers looking for new ways to 'beat' any new tests.
     
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  16. jimjams Expert Advisor ★ ★ ★ ★ ★

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    ^ Ilmor claim that this 5-stroke engine is a bit more efficient than a GDI engine, with better emissions. They also say that it might be possible to add on GDI to a 5-stroke to make it even more efficient.

    What they don't say though, is that the catalytic converter might take a long time to warm up, because the exhaust gases are considerably cooler (so the cat takes longer to become effective at removing NOx etc)
     
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  17. FirstHonda Premium Member Club Supporter

    I found this interesting.

     
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  18. jimjams Expert Advisor ★ ★ ★ ★ ★

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    One of the problems with GDI (aka FSI, SCI, HPI, CGI, SIDI, IDE) is that it's a relatively new development that might well take the petrol engine down the same path as the diesel, in that it requires a lot of extra controls and maintenance.

    i.e. lean burn and high compression has problems, and as I've said before, Rudolf Diesel was not looking for something that burnt oil, he was looking for high compression (because of its innate efficiency, as well as the fact that it did not require spark ignition).

    If you try to inject petrol into a very high compression engine when the piston is close to TDC, the vapour will explode, which is why a heavier hydrocarbon is used. The advantage of the heavier hydrocarbon is that its droplets burn rather than explode, but the problem is controlling the size of the droplets. As a diesel engine ages, you start to get issues with droplet size. Plus, the extra control systems to overcome the issues with lean burn and incomplete burn of the fuel, results in more maintenance issues.

    With GDI, the compression is not as high as a diesel, and, you still have to inject much earlier. So a GDI will never be as efficient as a diesel, and along with that you also get the lean-burn problems of a diesel. So a GDI has to have more complexity added on, which there is the possibility that GDI will show similar issues long-term as diesels do.

    However, the 5-stroke design is radically different. One of the issues for high compression and petrol, is the temperature in the combustion chamber. The problem with both petrol and diesel engines is the exhaust manifold. Ideally, it would be better to blow the exhaust gasses away from the exhaust ports so that the combustion chamber could cool down a tad. But with the exhaust manifold sitting there (needed for the silencer system), the combustion chamber remains hot. In a petrol engine, running at stoichiometry helps to keep the chamber cool, but if you raise the compression ratio too high, even a rich mixture will not prevent detonation.

    The 5-stroke is an interesting idea, and when you look at it, you wonder why it has only been thought of in the last decade. It does two things
    1. it allows the exhaust gasses to be moved further away from the exhaust ports (by allowing them to expand into a large cylinder), which means that a relatively high compression ratio (for a petrol engine) can be used
    2. it allows further work energy to be directly gained from the exhaust gasses (this was done in double and triple-expansion steam engines)

    As a result, the 5-stroke gains a lot of efficiency over the 4-stroke, particularly for petrol engines. IMO it's a shame that this simple way of raising the efficiency was not invented several decades ago (some argue that the Atkinson engine acted in a similar fashion but apparently not). There are bound to be some down-sides to this as well, but in principle it seems to offer a lot of prospect for the petrol engine.
     
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  19. FR-V Valued Contributor ★ ★ ★ ☆ ☆

    Pete Lincs
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    It would seem that in striving to get an internal combustion engine (be it diesel or petrol) to run without emmiting harmful substances we are only succeeding in strangling the power output and then overcomplicating the control systems in an attempt to get back to where we started.
    I run a diesel car (my first) because I tow a caravan on the continent and need the power, torque and weight of an old fashioned oil burning lump. Being a 2006 I-CTDI I don't have to worry about a DPF and with an annual mileage of 12 - 13,000 the sums add up. The car was totally unsuitable for its first private owner who put only 14,000 on it in 5 years! It took a good 6 months of running and a total fluid change ( and a new EGR valve ) to get it running as it should, but since then it has been faultless. I know the engine is of Germanic origin and have been told it is a VAG unit, but is too old to have been fitted with the software tweak.
    The old saying of "horses for courses" has never been truer, and the designers should stop trying to get a Clydesdale to run the National !
    What about going back to external combustion? Or did the gas turbine engine designs go to China with Rover?
     
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  20. Zebster Expert Advisor ★ ★ ★ ★ ★

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    It's a Honda engine... not VAG in any way! The fuel system (including the ECU) however is German, made by Bosch.
     
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