[Spehro Pefhany]

It is indeed a confusing name.
The "3 liter" is supposed to express the fact that it consumes less
than 3 litres / 100 km. It is a special edition of the Lupo with
lightened interior and skinny tyres.

The "real life" Priusses (Priae, Prii - whatever) we have here do
15...18 km to a litre (no documentation, asking real life owners on
local phora), a figure that is easily beaten by a average diesel car.

This is overall use. In city use (stop & go) the Prius may have a real
advantage.
I do like the hybrid technology - but I wait for the figures to
improve.

I can imagine e.g. a light 2 stroke diesel, operating in its most
efficient fixed rpm, driving a generator / accu combo; wheels driven
by electrics only - may have a better yield.

Don't diesel's have to be heavier to support the higher compression
ratio?

Somehow I distrust the factory milage figures. Makes me think of PMPO
power..

http://jalopnik.com/cars/news/classic-top-gear-the-prius-kinda-blows-buy-a-diesel-186004.php

I trust the test figures in a comparative sense. OTOH, I've not driven
a diesel that wasn't smelly, noisy and with crappy performance
compared to a gas engine. We won't easily put up with that sort of
thing here, nor is the lack of diesel pumps conducive to adoption. And
yes, I've driven a modern mid-size (VW Passat) diesel in several
European countries.

Best regards,
Spehro Pefhany

 

[Eeyore]

I can imagine e.g. a light 2 stroke diesel, operating in its most
efficient fixed rpm, driving a generator / accu combo; wheels driven
by electrics only - may have a better yield.

I'm pretty convinced that would be much better. And don't run the engine for shorter journeys.

I'm not sure that 2 strokes will meet emissions limits though.

Graham

 

[Eeyore]

Don't diesel's have to be heavier to support the higher compression
ratio?

Typically they are. They need to be stronger rather than heavier really.

I trust the test figures in a comparative sense. OTOH, I've not driven
a diesel that wasn't smelly, noisy and with crappy performance
compared to a gas engine. We won't easily put up with that sort of
thing here, nor is the lack of diesel pumps conducive to adoption. And
yes, I've driven a modern mid-size (VW Passat) diesel in several
European countries.

I drove a Peugeot 1.9 turbo diesel as long ago as 1988. It was pretty brisk. Performance seem to
be less of an issue with diesels these days although they don't rev as fast.

Graham

 

[Spehro Pefhany]

Typically they are. They need to be stronger rather than heavier really.



I drove a Peugeot 1.9 turbo diesel as long ago as 1988. It was pretty brisk. Performance seem to
be less of an issue with diesels these days although they don't rev as fast.

Graham

How about noisy/smelly?

Best regards,
Spehro Pefhany

 

[Eeyore]

How about noisy/smelly?

I got caught behind a smelly one the other day. It was a 1996 or thereabouts model and seemed not to
be in the best state of tune (it was smoking a bit too). You get petrol cars that are equally
offensive. Mostly diesels don't seem to be very smoky or smelly these days although buses often seem
to be rather poor.

As for noise, some seem worse than others. The best examples are quite quiet now.

Graham

 

[Rich Grise]

Typically they are. They need to be stronger rather than heavier really.


I drove a Peugeot 1.9 turbo diesel as long ago as 1988. It was pretty
brisk. Performance seem to be less of an issue with diesels these days
although they don't rev as fast.

I won "designated driver" one time, and drove this guy's Mercedes 300D.

What a pig! Had horrendous blind spots, and went 0-60 in about 10 minutes. ;-)

Thanks,
Rich

 

[MooseFET]

In city driving it's regenerative braking that can make a huge difference. The
complexity of shoving electrical and ICE motive power through some combined
transmission seems plain daft though. The series hybrid (in which the ICE simply
recharges a battery) seems far more sensible all round.

No, I disagree. The dual electrical machine design beats the series
system hands down. Having the engine go straight to the wheels when
it makes sense to do so makes the demand on the electrical system way
less.

 

[MooseFET]

Sure. It's interesting to see that they've actually achieved it, with
significant mileage improvment to boot, in a practical production car.

I suspect that many of us in this news group such as those who have
done things like DC-DC converters would say that any car that doesn't
do that is an example of bad design. The auto industry is still stuck
largely in the stone age. They are a little like the folks who club
dinner but have a transistor radio.

 

[MooseFET]

3-cylinder? Well, if you want real economy, an electric scooter with
SLA battery charged from a SMPS brick is about as far as you can go.

Take a modern bike and add a good electric motor and battery and it
will do even better.

 

[MooseFET]

Don't diesel's have to be heavier to support the higher compression
ratio?

They usually are bigger and heavier but that is partly because when
you are designing the engine for a train you don't worry about
weight. The forces in a high performance gas engine are higher than
in a diesel.

 

[MooseFET]

How about noisy/smelly?

The new ones are nearly odorless. The ball in a coffee can sound is a
lot quieter on the new ones too. One of the companies has an
experimental engine that uses a cute trick to refine extra oxygen out
of the air and add it to the intake. This raises the burn temperature
enough to eat up all the bad stuff.

 

[MooseFET]

On Wed, 01 Aug 2007 07:15:06 -0700, John Larkin

For a given shape, at automotive speeds, I think there is a square law
relationship between air speed and drag.

No thats a cubic law. The energy per mile is the square law one.

 

[MooseFET]

You are correct at higher speeds. The relationship isn't simple it seems.http://en.wikipedia.org/wiki/Drag_(physics)

Drag coefficient can make collosal differences too.http://en.wikipedia.org/wiki/Drag_coefficient

Unfortunately current US styling (the trend for truck like 'slab fronts' ) is producing
cars with greater rather than lesser drag.

The shape of the back controls the drag more than the shape of the
front. This is why the shape gets tot he full width fairly quickly
and then slowly tapers to the back.

The current hybrids also use skinny tyres to reduce rolling resistance. I hate to think
of the adverse effect on road holding.

There is basically no difference in the traction. Wide tires look
cool but below a certain amount of force per unit area of rubber give
no traction advantage. The traction loss in thing tires is because
the force on the surface is high enough to rip bits of the rubber or
the road loose. They modern materials in the tires are less subject
to this problem. The cars we are talking about are quite light too.

 

[Guy Macon]

Where do you think the electricity comes from? An electricity well?

It comes from an open-pit electricity strip-mine.

 

[Don Klipstein]

On Aug 1, Spehro Pefhany <[email protected] wrote:

No thats a cubic law. The energy per mile is the square law one.

Energy per mile is proportional to force of drag so both are
square laws. The cubic law is power used to overcome drag - airspeed
squared times groundspeed.

- Don Klipstein ([email protected])

 

[MooseFET]

On Wed, 01 Aug 2007 08:46:53 -0700, John Larkin

On Wed, 01 Aug 2007 08:26:13 -0700, Jim Thompson

[snip]

You need to look at engine horsepower and torque versus RPM as well.
Don't tell me what I need to do.

Eh? Didn't get any last night, John? You sure are cranky ;-)

I think, if you will follow my advice, see the horsepower peak in that
region as well.

...Jim Thompson

I wonder at what speed a 500HP 'vette is most efficient? ;-)

When its in the shop and you take a taxi home.

 

[Guy Macon]

I wonder at what speed a 500HP 'vette is most efficient? ;-)

You get 500HP out of your Chevette?

 

[Eeyore]

No, I disagree. The dual electrical machine design beats the series
system hands down. Having the engine go straight to the wheels when
it makes sense to do so makes the demand on the electrical system way
less.

Why's that an advantage ? It also means you can't have 'meaningful' true electric only
operation of it, plus it requiresa gearbox which otherwise may not be needed at all.

Graham

 

[Eeyore]

There is basically no difference in the traction. Wide tires look
cool but below a certain amount of force per unit area of rubber give
no traction advantage. The traction loss in thing tires is because
the force on the surface is high enough to rip bits of the rubber or
the road loose. They modern materials in the tires are less subject
to this problem. The cars we are talking about are quite light too.

I'm not talking about traction, I'm talking about road holding / handling. I know American roads don't have corners (or at
least from the way US cars drive you'd think that was the case) but we do here.

Which reminds me... why do Americans seem to want such big engined over-powered cars when most of them fall off the road
so easily if you use it ? Is it just a macho thing ?


Graham

 

[Nobody]

Why's that an advantage ? It also means you can't have 'meaningful' true electric only
operation of it, plus it requiresa gearbox which otherwise may not be needed at all.

The disadvantage of an all-electric or series hybrid vehicle is that the
maximum total power is constrained by both the ICE and the electrical
system, while a parallel hybrid can potentially combine the two, or at
least provide a more powerful ICE for motorway cruising without having to
size the electrical components to match.

A secondary consideration is that the generator losses subtract from any
efficiency advantages of the electrical drivetrain.

But mostly it's a case of having to size the electrical system to the
power requirements for motorway cruising even though it has fewer
advantages over a mechanical drivetrain in that context (i.e. regenerative
braking is of no benefit).