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As a converted diesel user could someone explain why on new family sized cars the turbo-diesel car costs approx. £1000 more than the petrol equivalent. Also why are we the only Country in Europe where diesel fuel costs more than petrol.
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Why are the cars more expensive? Because the manfacturers want them to be - who knows why? To dissuade people from buying them as they last longer than petrols? Because they can by playing on "higher building / development costs" to make more profit?
Why is the fuel more expensive than on the continent? Because it carries much more tax in the UK. Most other contries give a tax break to diesel as it is more environmentally friendly - but not the UK Gov who are hell bent on extracting every last penny from motorists. If everybody switched to diesel this would blow a large hole in the public finances, and income tax would have to go up.
It's a consipracy!
Richard
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Richard,
Yes, the tax on diesel in the UK is higher than in some other countries, but don't think other governments wouldn't leave a chance to let motorists pay go amiss!
In other countries, roadtax on diesel cars is considerably higher than on petrol or GPL (LPG) powered cars.
No such thing as a free ride!
Robert.
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Going a little out of the way with this but does anyone know why 10 yrs ago LPG was big in Spain and France but now seems to have dwindled whereas diesel powered cars are very popular.
Is it simply because diesel is so cheap or because they have come to the conclusion that LPG is a waste of time.
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Diesel engines are more expensive because they have a turbo and a very high pressure pump and heavier components and bigger cooling systems and bigger clutches and stronger transmissions and more NVH material and vacuum pump and EGR etc. etc. Enough explanation?
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Diesel engines are more expensive 'cos punters will pay the premium. The perception in Pete's post helps the maunufacturer rationalise that in the mind of the customer.
How do prices for petrol/diesel vary in France, Germany or Holland?
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The thing that's always foxed me is that the pricing of Diesel on the continent is so obviously set up to encourage use, thereby implying that they think its environmentally friendly. And in this country, we "apparently" think the opposite!!! Personally, I'm with mainland Europe on this one...and I've no opinion on the environmental issue until someone backs up theirs with some figures which justify why its dreadful here but fine in Italy.
Splodgeface
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Fuel/Diesel/Petrol prices across Europe (pence/litre):
www.see-search.com/business/fuelandpetrolpriceseur...m
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Pete,
I think the question was "Why is a turbocharged diesel much more expensive than a naturally-aspirated diesel?" but, even so, I don't think you were far off the mark.
As you say, diesels cost more to make anyway, though the cooling system shouldn't need to be any larger because the diesel converts more of the fuel energy into motive power rather than waste heat.
Turbo diesels cost a lot more than N.A. because the engine is capable of producing much more power so it usually needs stronger engine components (crankshaft etc) and possibly a stronger transmission. Then there is the cost of the turbo and perhaps an intercooler. On top of that, turbo cars tend to have higher spec injection systems than their N.A. counterparts. The oil pump probably also needs upgrading as it has to feed the turbo ... and so it goes on.
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Dizzy
The original question does say 'why is turbo diesel more than petrol?' That's what I answered.
Cooling systems do need to be bigger on Diesels because the coolant temperature is lower and so a bigger radiator is needed to dissipate the heat
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Pete, please accept my grovelling apologies. The original question was perfectly clear but I still managed to mis-read it.
However I can't quite grasp what you are saying about lower coolant temperatures needing a larger radiator. I could well be wrong but I thought an indirect injection engine produces quite a lot of heat that has to be got rid of via the cooling system but modern direct-injection engines don't produce as much waste heat as petrol engines. I'm here to learn!
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Diz - I'm a bit puzzled too, but Pete may be referring to the temp at the cool end, not the hot end? Other things being equal, as a diesel burns less fuel per mile than a petrol engine, it should follow (IMHO) that the diesel will produce less heat per mile and thus a slightly 'less hot' coolant. If we assume that the intention is always to return the coolant at (say) 40°C, that should mean a diesel would need a smaller rad? This argument takes no account of whether the diesel wastes proportionately more or less heat than the petrol engine - any knowledgeable auto-physicists listening in? (Toad will say one will be along in a minute).
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Dizzy and Andrew. Interesting and I?m not sure about this but relating it to heat transfer such as your central heating radiator.
Transfer of heat from this relates to the differential between temperature of the radiator and the ambient air temperature surrounding it.
As the air temperature gets higher the transfer decreases until ultimately (if it were possible) the air temperature equalled the radiator temperature no transfer can take place.
Fairly basic I know but thinking about what Pete is saying I would imagine that if the water temperature passing through the radiator of a diesel engine was normally at a lower temperature than a petrol one, it would mean that a diesel needs a larger heat transfer area than its petrol equivalent to reduce it to its desired return temperature.
Does this make sense............ I think so.
alvin
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Dizzy
Both indirect and direct injection diesels are more efficient than most petrols so less heat is put into the coolant as you suggest. However, diesels always run a lower coolant temp than petrols as governed by the thermostat. (Typically in the 80's for diesel and 90's for petrol). This results (as Alvin says) in a bigger radiator being needed because the temperature differential is less. This more than outweighs the reduced heat that needs to be got rid off.
The reason diesels have a lower coolant temp than petrols is because of the heavier castings used in a diesel. It is harder to get the heat from the cylinders into the coolant due to greater metal thickness. Also, when you switch off the engine, there is more heat stored in the castings which would result in the phenomenum of 'switch off, boil over' that most of us have experienced. Hope this explains some things.
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Thanks for that, Pete. It just shows that we are never too old to learn (I hit the dreaded 60 in a few days time!).
I now realise what you mean about the different temperatures and how the thermostats differ because of this. Certainly 'our' diesels (Perkins) had typical start-to-open temperatures in the 80s, even in the 70s for some marine engines, whereas on my BMW it is 92 degrees.
On the other hand, on my Triumph 2500 petrol engine the start-to-open temperature is only 82 and was about 10 degrees less than that with the original bellows thermostat! Perhaps the logic has changed over the years or varies from make to make.
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Petrol and diesel cars both put around the same proportion of waste heat into the engine coolant.However proportionally more heat is lost through the exhaust pipe in a petrol engine due to the lower efficiency.
I don't go along with the lower coolant temperature theory - temperatures are kept as hot as possible to increase engine efficiency for petrol and diesel engines... a 1.4 peugeot petrol engine uses the same thermostat (with same opening and closing temp) as the 1.8 diesel version.
My theory is diesels have larger capacity radiators because they generally get workd harder being used for towing etc. A cooling system has to be designed for the worst case scenario of lugging 4 passengers + trailer up a hill on a stinking hot day..something diesels are very good at
Steve
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Steve
It is well known that Diesels have poor heater performance even at stabilised temperature. This is because they reject less heat to coolant. I agree the exhaust is cooler also. If the engine is more efficient, then in general less heat will go to coolant and exhaust.
I cannot dispute your claim for the Peugeot petrol and diesel having the same thermostat but this is not the case with most engines. There may be some other reasons why the Peugeot can use the same thermostat.
Both petrol and diesel cars are designed for towing trailers and in the case of Ford, the requirements are the same.
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Pete
I would suggest that the only reason for the thermostats being the same is that both engines operate at the same temperature! - in the case of the peugeot XUD engine this is 93 deg..this is a very common unit and is typical of many small diesel engines. Both petrol and diesel engines operate at higher temperatures than previously because of better oils and the need to increase engine efficiency.
For a diesel operating at full power and at low speed (as when towing) the rate of heat-rejection relative to the brake power output is significantly higher than a petrol engines despite the increased thermal efficiency - a result of the exhaust gases being rejected at a lower temperature and rate due to the lower engine speeds of a diesel.
The latest direct injection diesel engine equipped cars might suffer from slow heater warm up compared to petrol when operated at light loads but once stable temperatures are met their is more than enough waste heat available
Steve
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doh! my middle paragraph should read ..
For a diesel operating at full power and at low speed (as when towing) the rate of heat-rejection to the COOLANT relative to the brake power output is significantly higher than a petrol engines despite the increased thermal efficiency - a result of the exhaust gases being rejected at a lower temperature and rate due to the lower engine speeds of a diesel.
Steve
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