Are diesels losing their old boy image

[pgarner]

Originally Posted by Poddy

not sure if the extra torque would count for much with 60bhp less but thats just my understanding.

i could be wring

depends on where in the rev range it was used.

say both were tottinling around 2500rpm and both put the foot down the diesel would pull away 1st

[HDi fun]

Definitely. That's why in general driving (where you don't have any need to go near the red line) high tech diesels feel so bloody rapid. They are, too. It's not all an illusion.

Some diesels still have annoyingly narrow 'useful power' bands but that, too, is disappearing with the widespread adoption of both variable geometry turbochargers and ever more ridiculously outrageous fuel injector rail pressures.

Petrol engines are progressing as well though. They've been deprived of development cash for some time (because of the love affair with diesel in recent years) but VAG's veritable arsenal of TFSi engines should not be ignored. Nor should Ford's brilliant 5 cylinder 2.5 turbo unit (315bhp in the Focus RS!).

[indiaman]

Diesel engines are inherently more efficient than Petrol engines, the new generation of Diesels are way ahead of their petrol counterparts. way to go, Diesel!!!

[HDi fun]

Let's just hope that the fuel companies don't start selling fuel by mass instead of volume. The calorific value of a kilo of diesel is similar to that of a kilo of petrol.

I am a hardened diesel fan but I do try to be 'diplomatic' to satisfy the boneheads who will still argue that a 80bhp petrol car will outrun a 300bhp diesel one.

[turbonutter69]

Who argues that Hdi?
Obviously a 80bhp petrol will loose to a 300bhp diesel. But so would the diesel if it was the other way round.
Diesel are more fuel efficient than petrols but that is out the window these day due to the running cost of diesels.

[HDi fun]

Everythings too bloody expensive to run these days. If you could invent a car that ran on tap water they'd tax that as well.

[cavy andy]

they lost that image with common rail diesel with less engine clatter and petrol rivaling power. With the price of fuel they realy do make more sence

[HDi fun]

Originally Posted by cavy andy

they lost that image with common rail diesel with less engine clatter and petrol rivaling power. With the price of fuel they realy do make more sence

At the expense of opening some old wounds I think you generally get more performance £ for £ with diesel. Where I'm less convinced is the reliability over extended mileages.

Dual mass flywheels, hydraulic engine mounts and outrageously complex fuel injection might well take their respective tolls over ten years of ownership. These are expensive parts to replace outside of the usual 3 yr warranty.

[turbonutter69]

But with diesel being dearer than petrol is it actually more economical?

[HDi fun]

Originally Posted by turbonutter69

But with diesel being dearer than petrol is it actually more economical?

Very possibly not.

I've thought this for some time if it's a long term proposition. For performance £ for £ at purchase price and fuel economy I'd take diesel over a similarly priced petrol model so long as someone else is paying for the long term maintenance.

Most of the current diesel technology is ridiculously complex and there is not yet a network of independent specialists who really know what they're at.

At the moment I'd be very likely to take a 6cyl 3.0 NASP petrol (no turbo means no heat problems, no need for sixty quid a fill engine oil etc etc) over a 4cyl 2.0 twin turbo diesel as a long term option. Performance wise, in a large car they'd be comparable. THe diesel might well have a slight advantage.

But the diesel WILL demand more prescriptive servicing and over time the costs add up, even without the slightly higher fuel price.

So, in short, I'm torn.

[turbonutter69]

Thats exactly my point. Diesels are better on fuel but the fuel costs more so it's a no win as far as I can see.

[HDi fun]

Originally Posted by turbonutter69

Thats exactly my point. Diesels are better on fuel but the fuel costs more so it's a no win as far as I can see.

Not that much better though. The stresses that a high performance diesel engine puts upon its components are huge.

I still would not go for petrol just for performance because I think that is outdated now. Diesel engines do deliver the torque and acceleration in spades; they're also very quiet and refined. Until it's out-of-warranty-maintenance-time. DMF £1000; most common rail diesels still use belts for the valvetrain drive; lots of petrol cars use duplex chains.

But I certainly wouldn't buy diesel simply to save money. I'd buy new for the huge range of usable torque. You can stay in the same gear from 1500rpm right to 4500rpm with max torque all the way with a diesel. Treble your speed in one gear - 30-90mph without a change. They are quick. A peaky petrol engine would require one, maybe two changes.

Much as I promote diesel, I was it's earliest hater, and I'm not fond of the way the economics of owning one long term has panned out.

If I bought, say, a 4yr old 5 series with the 4.4 V8 petrol engine I will rarely see more than 30mpg. But the engine is classicly simple and does not demand much more than servicing at the correct times. It does not require specialist attention every 12,000 miles.

If I kept that car 10 years I'd be no poorer than having 3 Renault Laguna 1.9dCi models in the same period.

[WLBjork]

Depends on mileage, and how you treat the car.

To put things into perspective, driving 10,000 miles a year and achieving the average fuel economy displayed at whatgreencar I found the following costs:

Octavia vRS Diesel - £1150 fuel + £150 road tax = £1300

Octavia vRS Petrol - £1440 fuel + £215 road tax = £1655

BMW 5 series with 4.4L engine = £2240 fuel + £405 road tax = £2645

That's roughly saved me the cost of the DMF in a year - and I'll only need one every 5-6 years.

However, it seems it is possible to recondition the DMF, which works out cheaper (out of warranty anyway) - one chap had his DMF reconditioned and a new clutch for a total of £335 (interestingly at the Clutch Centre in Arnold or Basford, here in Nottingham), and it lasted for at least another 40K miles (even after a remap).

[pgarner]

Originally Posted by HDi fun

Dual mass flywheels, hydraulic engine mounts and outrageously complex fuel injection might well take their respective tolls over ten years of ownership. These are expensive parts to replace outside of the usual 3 yr warranty.

these are also on alot of petrols now.
OEM clutch, DMF and release bearing plus fitting im looking at close to a grand

[HDi fun]

Petrol engines are a lot less savage on these components. The flywheel torque is much lower

[jarrus]

Yes this is what I was going on about in another thread,
No wonder my old rattley mechanical inject turbo diesel are so good, yes a new car will do more mpg but I won't need to get the dealer to plug in his diagnostic box everytime something goes wrong, but cause it's sooo simple it doesn't go wrong....
and it's not like it's a slouch though I have surprised a few pd140's

But yeah I know what you mean though, the torque delivery on turbo diesel's is very savage, the engine might last long but you can't help but thinking how many more clutches, flywheels, driveshafts and gearboxes (and set's of tyres come to think of it)am I going to destroy during my car's life time,

It's a very tough call and I've come to the awkward time as well HDI where I'm not sure whether to stick with diesel or go for a petrol....
a gti-6 does sound nice, so does a lancia delta 16v
but so does a 306 2.2 hdi.......

[HDi fun]

You can fit a solid flywheel in place of the DMF - it comes as a complete kit as the clutch is different as well. Personally I'd not do this, I think that the angular torque reversal (which is quite significant in a 4 cylinder engine) could do more harm to the engine itself over an extended period.

[jarrus]

What you have to considered is that torque is a measure of the engines turning force and hp is a measure of "work done" so to speak, and hp is also directly proportionate to torque

So really a turbo petrol generally speaking is producing it's hp though the big amount of torque that the turbo is serving up,

and high revving petrol's produce there hp because they work very hard as in very high up in the power band,

as for diesels the big amount of torque they have is down to the high compression ratio and big boost,

From what I can work out that is why a turbo diesel that is producing the same torque as a turbo petrol will never put out the same power because the petrol revs higher, and the same power petrol and diesel, the diesel will always produce far more torque due to the massive boost and compression,

That is how I see it...