"Burgerman" <burgerman (AT) ntlworld (DOT) com> wrote

Yes you do. Then claim you'd had too much to drink.

No, the point I'm making is that you're either unsensitive to change or
lying.

Point being that you have read what I've written and are ignoring it.

Then filling in gaps in your own knowledge by making claims that have almost
no relevance to what happens at the street.

Hahahahahahahahah. Yet again you insist that you are able to use any engine
from idle (for arguments sake) upwards.

Later on you go on to claim that using an engine below where it works as
best it can is foolish.

By your own words, you try to drive the turbodiesel like a petrol. You harp
on about accelerating then needing to change up, which means in the majority
of cases you're in the wrong gear.

I'll go on.

Take it to the manufacturers.

Your own minivan has a 3.3 *naturally aspirated* petrol or some turbodiesel
instead.

Why no turbopetrol? Oh, right, because this would reduce the effectiveness
of the V6. Uh-huh.

So?

Yes. That's because they're better, they're quicker, quieter, go further to
a tank and have improved engine longevity.

Yes. This is precisely where one keeps the engine speed. I appreciate that
this is a hard concept for you to grasp.

Petrol engines need to be kept at higher engine speeds for better
performance.

Turbodiesels are kept lower.

You clearly struggle with this.

Yes that's right, if you accelerate the engine speed increases. Except the
difference is that for a similar maximum power output engine, the
turbodiesel has much stronger acceleration at lower engine speeds compared
to the petrol. One drives the turbodiesel to make use of this, just as one
would drive the petrol to use the greater power higher up in the rev range.

This doesn't make one bad, simply, different.

No I disagree; inflexibility is the reason why the driver must change down a
ratio for a gradient or overtake. This is because it won't go up the hill
in the higher gear.

Except that like for like maximum power engines have quite a difference in
their delivery at 3,000 rpm. Not to mention that the two have different
gearing.

For best acceleration in the petrol car here you'd change down to increase
the engine revs.

In the turbodiesel you won't bother, you'd probably keep the engine speed
somewhere closer to 2,000 rpm.

Thus yes, absolutely, this is what would happen except people don't drive
like this because it isn't using their engine to the best of its abilities.

It isn't though.

I reach a hill in XYZ turbodiesel with the cruise control engaged at the
national speed limit, somewhere around 2,300 rpm. I ascend the hill with
barely any noticeable difference in speed. As the revs drop the torque
increases. Less revs, more torque, lower power, probably, but from 2,300
rpm we have a good 500 rpm until the turbocharger stops doing its
turbocharger thing and becomes an obstruction.

I try same in a similar priced, similar maximum power petrol car. Say 2,700
rpm. The car struggles up the hill and bleeds speed. As the revs drop so
the torque is reduced. Less torque, fewer revs, less power. With the
shorter gearing it loses more revs for a given reduction in road going
speed. The situation is resolved by changing down.

But you claim that the petrol engine is usable at low speeds.

Except it's more gear changes to keep the power output levels high on the
way up a gradient.

*Stacks* more torque at the flywheel, which more than makes up for it, going
on in-gear acceleration times.

Nullified by taller gearing.

Minimal.

Extra noise outside when cold. On the hoof or when warmed up, the cooling
fan is noisier. The air conditioning condenser fan is noiser than the idle.

It's entirely possible that your damaged hearing has removed some of the
frequencies that petrol engines produce thus you only hear the diesel
frequencies.

Maybe my hearing is the other way around. Who knows.

Go on?

Cars are built by robots.

It isn't.

No. Two and three speed automatics were used because of cost reasons
created by engineering difficulties, size constraints, lower speed limits,
lower noise and environmental compromises put into place by Governments.
They had serious complications for performance and economy. Electronically
controlled, four, five, six, seven speed transmissions have had just as many
benefits for diesels as they have with petrols.

Diesel automatics have been made for a long time.

It's by demand more than anything else. Citroen have manufactured diesel
automatics for the longest time.

So? You may struggle to buy a petrol anything in France.

No, the reason why diesel sales are very low in North America is thanks to
General Motors' diesels in the early 1980s being poorly engineered and
having huge technical problems. There's a resurgence in low fuel cost
vehicles in many States thanks to the hike in the price of oil. VAG have
sold their TDI Golf, Beetle and Bora for the longest time.

Because until manufacturers sell naturally aspirated diesels alongside we
can't do a like for like.

Where?

Cost versus cost is.

Power versus power is.

Market sector for market sector is.

We're not comparing engines, we're comparing cars.

Numbers.

Perception of the pain involved in constantly having to change down to
accelerate.

Partially. There's also an element of demand and market continunity.

So why don't they, then?

Comparing like for like maximum power figures, since plenty of European
countries derive tax on engine power.

And is flawed without reference to what happens out there.

People in the real world.

If it's an alien concept, just say so.

Correct. And why is that?

Market demand perhaps?

And yet nobody does? This isn't quite the case though.

Well here you're wrong. Oddly enough Saab have used turbocharged donks for
the longest time, the '98 to '02 9-3 used a range of atmo and turbo engines
from 2.0 through to 2.3s.

The 2.0t, that is the low pressure turbo, is a nice piece of kit. Never
quick, but a good deal more flexible gear for gear than the 2.0 atmo despite
being geared for 26 mph / 1,000 rpm in top compared with the NA 2.0's ratio
of around 23.5 mph / 1,000 rpm.

Yet the 2.0t revs just as well as the 2.0.

Curious that, isn't it?

Except the higher rev issues are not a problem... you're not making any
sense.

And so little relevance to what happens out there...

It isn't useful if it can't pull the skin off a rice pudding. Isn't this
your issue with an off boost turbocharged engine?

Little torque, few revs, little power.

Well I for one have yet to drive anything with four cylinders that'll "pull
hard" from idle in top gear without protesting and trying to shake itself to
bits.

Yet less crap than a petrol equivalent.

It's hugely important what we use since it's an overall package. You can't
spout off about road speed / gear selection / engine speed without reference
to a given car.

Otherwise we're comparing something like a Lupo TDI with a BMW V10 M5. And
that's hardly fair.

Even and some?

But has stacks more at these engine speeds anyway for the same maximum power
output.

Except the diesel has stacks more torque at the same engine speed. The
reason why you need to use shorter gearing is because the petrol engine
needs those extra revs to compete on a power output scale.

We all bow down to your superior knowledge then.

Echoes previous comment.

You don't think you need to think, you just waffle on about irrelevances to
day to day driving.

No you mean you'd have reference to the real world.

Show you what? Show you that you know everything there is to know about
turbodiesels on the road but have not managed to put this into perspective?

It isn't an illusion unless you believe fewer seconds to cover a given
change in speed is a lie.

Of course. The petrol is operating below its optimum. One should change
down.

You don't need to in the turbodiesel.

So what's the difference? Change down before accelerating, then have to
change up again when you reach your intended speed, or changing up during
acceleration?

If the turbodiesel is turning over at ~2,000 rpm in third gear at 30 you
don't have to change up until you reach 60.

If your petrol engine is turning over at ~2,000 rpm in third gear, you
select second, nail it, then have to change up at 60. Quicker? I'd expect
so. My Accord was.

That's more gear changes for the petrol not fewer.

If you accelerate in third gear in the petrol engine, you'll move the donk
from 2,000 rpm to 4,000 rpm, which is precisely where the turbodiesel has
better power production. The petrol model is *slower* over this increment.

See above then try it on the road.

But like everything, just looking at a bunch of tables or charts and then
claiming you know how its applied on the road is daft.

You claim to have done it.

Correct.

You don't need to.

Except it's a case of little, whoosh, change up.

Kinda like a petrol engine, except that's little, bit more, bit more,
whoosh, change up.

It's the short rev range that only says part of the story.

Short rev range + tall gearing = large speed range per gear.

Only over 5,000 rpm though, depending on the design.

And yet turbodiesels manage so much without running up against this
breathing limit.

The driver who constantly reaches this limit is unable to drive properly.

And it isn't a problem with an automatic either.

Utter irrelevance since we're taking about cars.

Yet production diesels in rather ordinary cars have benefited from variable
geometry turbine blades for almost ten years...

You so need to drive something with a Mercedes badge and launch control.

Except they do, though.

Where?

Only from one perspective, though.

I couldn't fault mine other than the seats are not as comfortable if you're
over 6' tall and it's a bit boring. Very quiet, great petrol engine, decent
handling, decent ride, okay equipment.

Lacks a bit of soul in my opinion. I swapped it not because I disliked it,
but because I didn't like it.

The 1.85 goes from very little (under 2,500 rpm) to having a bit (2,500 rpm
to ~4,500 rpm) to going properly (~4,500 rpm upwards).

The 2.0 is quite a bit better lower down and the same gearing.

I'm sorry, but I can't take the opinion of somebody who makes a conscious
decision to ride a bike seriously.

Take a look at older generation donks. A bunch of the Sierras have a lovely
flat torque curve from 2,000 rpm to somewhere over 4,000 rpm.

Or, hmm, well it's close enough: http://www.dervman.com/kermitcurve.jpg

Ignore the figures because they're made up it's the shape that counts.

It certainly is in the case of the Ka.

It's one reason why I liked that engine... relatively good low to mid range
poke, exactly where I keep the engine most of the time.

But posts say otherwise.

Correct. I would have to change down a gear or two in the Accord,

That's exactly what you are doing with the turbodiesel...

By selecting higher engine speeds you are biasing your result in favour of
your beloved petrol, which can only do diddly squat lower down in the rev
range.

I do.

No it's less flexible, you have to change gear more to change speed, not
less.

?

You'd think so. I'd think so. It is quicker but only if you change up
somewhere between the redline and the limiter in every gear.

But that isn't what happens with any like for like maximum power petrol
versus the turbodiesel.

You don't want to discuss this because the Saab wees all over the Accord for
towing stuff? Because it does.

Light car? Perhaps in something like a Citroen AX you have a point. But in
case you didn't know, stuff in the Mondeo class these days is around ~1,500
kg.

Yeah why not. VAG sold a 1.8T with 150 bhp and 177 ftlbs. They also sold a
1.9 TDI with 150 bhp and 236 lbsft.

Fiat manufacture a 1.9 diesel with 150 bhp and 225 lbsft, also used in Alfa
Romeos, Vauxhalls and Saabs.

The PSA group manufactured a 2.0 low blow turbo with 150 bhp and 173 lbsft
of torque.

Saab's 2.0t used in the 9-3 and 9-5 with 150 bhp and 177 lbsft.

Now I need to borrow stuff back to back. I suspect the diesels' 0 - 62
times favour the petrols but the 30 - 50 or 30 - 70 favour the diesels.

See above.

So you can't drive it the same way as the turbodiesel.

Right, so what you're essentially saying is if the Honda isn't pokey enough
to be driven at 2,000 rpm then it's less flexible than my Saab, which will
happily be driven at this engine speed. Even with the shorter gearing of
the Accord it needs down changes to perform.

No, I have more low down torque and the same speed range in the gears.

Because when I'm cruising I don't need to change speed... and because it
would be pretty stupid to cruise at 70 in third in the Saab.

Honda Accord at 70 indicated: 3,250 rpm. I should use third? Meh.

In the short term it may be. I get bored spending time on a fuel station.

I compare for what my cash can buy and what's available.

Little torque at low engine speeds means little power.

High torque at low engine speeds means more power.

The next time I'm in a Prius I'm remember that. But I don't think I've
driven a steam powered machine.

See other comments about power to weight.

So basically you don't understand how the four cylinder manual turbodiesel
drives and therefore berate it.

The TiD's peak torque is a quoted 192 lbsft from 1,900 to 2,500 rpm. No
great shakes really.

Rather than nothing, better than nothing, more, yeah here we go, then torque
falls away.

Across the same speed range too.

Yes absolutely, except as your girlfriend may discover, keep the Honda's
engine speed in the low lift camshaft / longer intake tract mode (under
~4,000 rpm for the 2.0) and it's not too bad with petrol. Use the higher
lift zone and it's disproportionately thirsty.

Most economical or most efficient, because the two things are different.

Some machines are more economical at a higher engine speed and lower gear
for some speeds, aie that's certainly true. But they're also quieter in the
higher gear.

But what if peak torque is at the 2,000 rpm point?

I don't give a stuff about noise outside the car to be honest. Given the
idiot who tries to block me in half of the time (and has yet to realise that
when he runs into my tow bar it sets the alarm off, damages his bumper but
doesn't do anything to the Saab).

At a cold idle the Saab has a delightful diesel clatter.

On the road I can't tell any difference.

It isn't usable at 750 rpm. It will drive the air conditioning compressor
and the alternator but that's about it. It certainly won't pull itself
along the road.

If you try to drive it like a petrol, yes.

Petrols are an even bigger compromise if you try to drive 'em like a
turbodiesel.

I mean a reference chart on a screen or page isn't really useful when I'm
driving it, since I can go by how well it accelerates - or not - at
different speed / gear selections.

Even my Mondeo TD spooled up under 2,000 rpm.

Cue some turbo waffle...

Yup, lots of waffle. You are missing the point.

As I have demonstrated there may be fewer changes and greater flexibility
compared to the weany-at-low-revs naturally aspirated petrol car.

So what? You're still trying to convince me that it's possible to
accelerate a car in the highest gear at idle speed up a hill.

And yet I can select a high gear much earlier than I can in a petrol car for
comparable acceleration and keep to the high gear through a much wider speed
range.

I am. You're the one hung up on trying to compare a small capacity three
cylinder TDI with a six litre plus V12.

Nah they're not crap, this is something that shoddy inadequate drivers
claim.

Have you actually driven any recent diesel automatics with six or seven
gears? Ever noticed that it's entirely possible to keep the engine speed at
or under 1,500 rpm simply by being moderately careful?

No of course you haven't. You'd been ranting on, Clarkson-like, about power
and stuff. Goodo.

Ivory Tower. Inadequate experience of real stuff on the roads.

And yet you do.

Oooooh goodo. So why don't you understand how they apply to the real world
then?

Ya and you can't apply this to the road, can you?

No you misunderstand. I don't give a stuff about the increased cost of
manufacturing the turbodiesel if I can buy it for the same as I can buy
something with a weany naturally aspirated four cylinder petrol engine.

I do give a stuff about running costs. That's why I didn't run a V8.

There's incorrect though. Try swapping the turbodiesel and naturally
aspirated petrol transmissions around...

Right, but as you said earlier on, finding something with four cylinders,
decent low down torque, no turbocharger and petrol is just plain difficult.
The point I was making is that the majority of ordinary petrol engines
produce peak torque above this 3,000 rpm point.

And in the petrol you have to change down sooner. Much sooner.

I could have told you that.

If it moves. Oh and changing gear over and over and over and over again.
Dropping to second when towing and encountering a gradient. Or worse,
dropping to first when you're towing something heavy.

Check again.

What part of, "low carbon dioxide / low fuel consumption / low noise levels"
didn't you read?

No no I mean all this nonsense about climate change and such gibberish.
They calculate fuel consumption by carbon dioxide emissions.

Correct, issue is that you have to either keep the petrol on the boil and
increase fuel consumption or accept that you need to change down when
acceleration or power is needed.

You're clearly unusual in this respect then.

I can't get my head around how you would be unable to keep a turbodiesel on
the boil either.

This is how you drive the turbodiesel... D'oh.

Correct. So you change down into a lower gear, accelerate, then change up.

Rather than keeping the turbodiesel in the high gear of course.

Yeah try it then.

Correct.

More engineering "no compromise" stuff.

In high gears for relatively long periods of time.

It doesn't. Besides you're only opting to use the lower gears because that
suits the petrols...

Peoples' perception doesn't allow them to overtake other vehicles without
using second and third.

And people have to change down to access more power.

Except people buy cars, though.

At marginally greater sticker cost.

Not really.

No, the turbodiesel is sold as a viable alternative to a naturally aspirated
version.

Ya? And you think that turbopetrols are cheap?

That's classic gear set up; these days manufacturers do deliberately raise
the gearing for consumption purposes. Sad but true.

And it makes modern petrol engines less and less suitable for ordinary
driving conditions...

Why would you not? Perhaps because after a while you'd get bored of 5,800
rpm in third at 70?

You don't know that. All this stuff about peak efficiencies and similar,
point is that there's a compromise. If a car will drive along at 70 in 6th,
why shouldn't one use that ratio? It also encourages people not to change
speed as much, but I appreciate that cruising is an alien concept.

No, the point is you have to.

Correct, there's no need to drive it this way. You can. Don't need to
though.