In message ,
writes

Sorry , I disagree. The only thing in diesels favour is its lower fuel
consumption. Thats it. Diesels max rpm are limited by the physical
characterstics of the fuel , which results in a lower max power for a
given engine size than a petrol engine (when was the last time you saw
15,000 rpm diesel motorbike engine or a diesel F1 car?) , their
throttle response frankly is rubbish in comparison , they're heavier
and the combustion process at full power is a mess (how many times have
you seen even a new diesel vehicle belching out black soot) and because
of this they can't use catalytic converters and to get any reasonable
power out of a diesel you have to shove on an expensive turbo. Yes
diesels put out more torque than a petrol engine of equiv size but
thats easily solved by different gearing on the petrol. The lack of
power however can't be solved by gearing.

To be honest diesel engines are a prehistoric bit of kit which belong
alongside steam engines in a museum and which only still exist because
of their *slightly* higher fuel efficiency than petrol (and if you
measure it by weight of fuel used and not volume the story isn't so
rosy for diesel as you'd imagine) and slightly less maintence. If
diesel prices were to rise relative to petrol the diesel car (and
possibly other vehicles) would soon vanish off the roads and the sooner
the better IMO.

B2003
I sometimes try trolling, but at least I'm honest about it, and I know a
few facts before I start, the rubbish above shows just how little you
know about the different fuelling systems in current use on just cars
alone.
--
Clive

In message , Dave Plowman
writes

They're still incredibly inefficient compared to a decent electric
motor - energy in against energy out.

Also, the difference between a petrol and diesel of similar output both
at full power isn't that great.

--
Whilst both are true, electricity has to be generated somewhere and
that's where the losses occur. As for Petrol v Diesel, neither are
driven flat out for very long in the life cycles but the efficiency of
the unloaded Diesel far exceeds the unloaded Petrol at similar low
powers.
--
Clive

In article m,
Martin Underwood wrote:
I'm comparing two engines with the same rated power and almost identical
capacities. The diesel has a torque that peaks to a higher level than the
petrol and at a lower engine speed. That sounds like a good example of
higher torque at lower engine revs - a common feature of diesel engines.

Try comparing a petrol turbo with a diesel turbo - that's fairer.

--
He who laughs last, thinks slowest.

Dave Plowman London SW 12
RIP Acorn

In article ,
Clive wrote:
Whilst both are true, electricity has to be generated somewhere and
that's where the losses occur.

That's not important when comparing efficiencies of a power plant.
Otherwise you'd have to take into account transport and refining costs etc
of any fuel.

As for Petrol v Diesel, neither are
driven flat out for very long in the life cycles but the efficiency of
the unloaded Diesel far exceeds the unloaded Petrol at similar low
powers.

The trouble is that it's never like for like. Powerful diesels - like BMW
ones - with say six cylinders, designed for refinement and power rather
than outright economy, tend to narrow the fuel consumption gap
considerably. You pays your money...

--
*The fact that no one understands you doesn't mean you're an artist

Dave Plowman London SW 12
RIP Acorn

In message , Dave Plowman
writes
Similarly, using a supercharger etc increases 'atmospheric' pressure
and the final compressed pressure. If you could develop a supercharger
which was super efficient, you could negate the effect of the throttle.
But you'd then have to adjust the fuel accordingly which would mean the
engine accelerating uncontrollably until it burst. One thing
overlooked with petrol and diesel (or steam) is that all reciprocating
engines have nil torque at TDC and because modern diesels have up to
five bursts of fuel between TDC for ignition and 90 degree after TDC
maximum torque, diesels will always win hands down. I find a lot of
people equate engine power with bhp and don't take torque into account,
hence a PP who was witering on about F1 engines.
--
Clive

"Martin Underwood" wrote in message
s.com...
"Nick Finnigan" wrote in message
...
"Martin Underwood" wrote in message
s.com...

I've always wondered: is it the fact that diesel engines use compression
ignition or the fact that they use different fuel which gives rise their
greater efficiency and their greater torque at lower engine revs?

It is quite possible to design an 'inefficient' diesel engine, but
no-one would buy a car with one instead of a petrol engine.

Do you have examples of greater torque at lower revs?

1.8i 16V Zetec
1.8 Duratorq TDCi

1.8 16v petrol
2.0 HDi diesel

Maybe the difference is partly due to the diesels being turbo-charged and
the petrols not being.

Yes, of course it is, the function of a turbo is to increase torque,
by increasing the amount of air per stroke.

Could this be a fairer comparison?
1.4 16v petrol

1.9 SDI diesel

Still different amounts of air per stroke.

In message , Dave Plowman
writes

Try comparing a petrol turbo with a diesel turbo - that's fairer.

--
He who laughs last, thinks slowest.
True.
--
Clive

In message , Dave Plowman
writes

The trouble is that it's never like for like. Powerful diesels - like
BMW ones - with say six cylinders, designed for refinement and power
rather than outright economy, tend to narrow the fuel consumption gap
considerably. You pays your money...

As you says

"you pays your money an you take
your choosy". Diesels compression ignition have the upper-hand over
electric ignition petrol ignition. I'f you don't know how, the I.P.
address is real. I don't have anything to hide.









--
Clive

In article ,
Clive wrote:
I find a lot of people equate engine power with bhp and don't take
torque into account, hence a PP who was witering on about F1 engines.

BHP is the product of torque and rpm. An ideal engine might have the peak
torque and maximum BHP as widely separated, rpm wise, as possible.

--
*I get enough exercise just pushing my luck.

Dave Plowman London SW 12
RIP Acorn

In article ,
Clive wrote:
As you says

"you pays your money an you take
your choosy". Diesels compression ignition have the upper-hand over
electric ignition petrol ignition.

In your opinion. Plenty would disagree. And fuel consumption isn't
everything.

I'f you don't know how, the I.P.
address is real. I don't have anything to hide.

What the f**k you on about?

--
*i souport publik edekashun.

Dave Plowman London SW 12
RIP Acorn