Advantages v disadvantages of a diesel!!!

i think they should share.

Reply to
Burgerman
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That's the one. I'm surprised you have heard of autospeed over there.

Fraser

Reply to
Fraser Johnston

I here of a lot of things car related, still using Australian Dollars over there as we don't trust you with pounds.

Reply to
Depresion

More likely an old CX judging by his wants in a car. Lets see, he wants the power curve of a 3 litre v6 with everything from 3000rpm lopped off...

Reply to
Burgerman

Actually repairing rotaries is big business too...

Reply to
Burgerman

Nehhh Would still be rattling smoking along to the finish, and leaving carbon dust on the strip...

Reply to
Burgerman

Ignoring issues of economy, for a given power, the diesel is better, because it's quicker(&), has a wider _power_ band(*), is _much_ better suited to normal driving and is more reliable.

(*)Yup, a wider power band - proportionally. The torque curve of a diesel drops off roughly linearly with rpm, but since power=rpm*torque, this gives the power curve a wide peak. e.g. 130BHp VAG Tdi, produces >90% of peak power from 2600-4600rpm, i.e. over 43% of rpm range. A petrol engine with ideally flat torque curve produces >90% of peak power for les than 10% of rpm range.

(&)because of (*) it's possible to be within a few % of peak power for a significantly larger fraction of the time than for a petrol lump.

For most people, the rev range above 5000rpm is never used, so the peak power of the engine is irrelevant, and the petrol is effectively much less powerful than the 'equivalent' TD.

So, basically, I like diesels because for the amount of money I can afford to spend to run my car, the TD is significantly quicker and more enjoyable to drive than the equivalent petrol.

Reply to
Albert T Cone

Ignoring your other coments, why exactly do you think "more reliable"????

Extremely questionable!!! Since you must be comparing turbo against more reliable non turbo petrol.

Depends how you drive or if you collect pension yet or not.

??????? Ahhh pensioner!

so the peak

Not to most people its not!

and the petrol is effectively much

Then its not equivelent. Aturbo petrol will destroy your diesel!

You said ignoring the economy???

the TD is significantly quicker

Extremely debatable, and depends what you compare to what.

and more

Reply to
Burgerman

Yes, but only because they have to. Even then the economy and power outputs compared to the diesel / petrol engined equivalents is s**te.

Reply to
SteveH

No, you resort to even more complicated ways of doing it like variable timing.

Reply to
SteveH
[...]

No car available with a 450bhp V8 can be considered ugly...

...even if it is.

A
Reply to
Alistair J Murray
[...]

5.0l, 450bhp V8 to special order, 3.0l, 265bhp I6 from September. A
Reply to
Alistair J Murray

Why do you keep bringing in 'less reliable' when you talk about TDi engines? - there's nothing inherently less reliable about the low pressure turbo in a TDi application.

Quite the opposite, in fact, the TDi lump will quite often outlast the petrol lump just because it's lower revving.

Reply to
SteveH
[...]

So, to sum up:

For Against Diseasel Cheap Nasty Petrol Everything Dearer

A
Reply to
Alistair J Murray

Incorect. (like my spelling)

Once running an oil film prevents any metal on metal contact, revs are irrelevant. Any oil company or car manufacturer will tell you almost all wear is due to friction when starting without oil pressure/flow. And oil errosion. And bearing surface corrosion between different metals.

About ten mins after starting a new shiny diesel car its begun! For starters: At idle it has huge loads and cylinder pressures to cope with due to no throttle plate, so full air load to compress to daft compression ratio. Its why they sound so stressed and noisy at idle. So apart from huge loading on crank bearings, small end and side loading on piston (which will cause wear only when the oil is dirty which happens fast!) you have much by products of combustion, and carbon, blowing past the rings into your oil due to high cylinder pressures that do not exist in the petrol engine. This is why engine oil in a diesel goes black so fast.

This carbon builds up fast in all diesels, and is very abrasive. And the acids and other combustion by products begin etching and corroding all the bearing surfaces, including the rings, pistons, mains, and big ends, and your fragile turbo. Next the heat in the turbo carbonises the oil, and dries out the oil leaving carbon in the turbos bearing for later on... In the meantime the oil film is squeezed thinly on the cylinder walls, and the crank bearings allowing the carbon saturated oil (made worse still by longer service intervals) to wear and errode the soft bearing surfaces and cylinder/piston etc. Meanwhile the less stressed petrol engine also has clean oil still... Since it has not much air to compress (throttle all but shut) under idle and most slow / cruise conditions.

Thes are only SOME of the reasons that diesels wear out faster, the addition of a turbo adds more complexity (and more low rpm loading still!) which can and do fail regularly. Turbos on diesels generally fail due to bearing or seal faliure caused by dirty carbonised oil and heat! Directly caused by the marketing departments decicion to extend service intervals to try and compete with petrol engines which dont dirty the oil even 1/3rd as quickly.

Would you like some more reasons??? There are a good few.

Reply to
Burgerman

Because the correct compression ratio and ignition curve and fueling is vastly different and they dont change it! If they did they would see a small power gain possible because of the octane. Same with propane.

Reply to
Burgerman

Eh?

For Volvo - their diesel I think is there own design, now (D5, as opposed to the legacy 2.5D I5 they used to use).

Plus Vauxhall produce blown petrols and diesels of roughly the same capacity, don't they?

Reply to
Douglas Hall

1 litre bike engine makes 170 without variable anything, and only 2 fixed ignition timing points!
Reply to
Burgerman

Snip slightly dodgy technical bollocks.

The real world says different.

Reply to
SteveH

Well I think it's deceptive - obviously if you are going to compare forced induction with NA engines, there's going to be differences in characteristics - but that obfuscates _why_ there's a difference in characteristics. It's not something inherent...

Fair comment.

I think of the comparison like this - Volvo's T5 engines, easily capable of mid to late 200s in the bhp stakes. Reasonably similar to many of the 4-ish litre V8s. What would I rather have and drive? The V8. Why? Because fuel economy will likely be similar given similar driving style - OK, a V8 car might have a heavier engine, and be generally a bit heavier - but roughly

280 bhp seems to have similar fuel economy, so long as there's not a major difference in the weight of the car. And the V8 will probably feel better from lower in the rev range, before the turbo has spooled up - plus higher up in the rev range, it's got more cylinders, and more valves.
Reply to
Douglas Hall

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