40 mpg Prius vs 50 mpg European Diesel cars - Page 5

 

Back in the '70's I remember driving a small Toyota diesel pickup several
hundred miles.  They might as well have replaced the gas pedal with an
on/off switch given holding it to the floor would just make 55.  The fellow
who owned it left it running in his driveway all night when it was -5F or
colder.  I take it they've improved, huh?

 
The big difference is undoubtedly the turbocharger. Half a bar of boost is
fairly standard for consumer gasoline turbos, but the diesel turbo (at least
the one in my truck) boosts three times that. It is very much like you
describe - foot to the floor - until the turbo gets spinning, but then the
power becomes phenomenal.

Mike

        perfb@yahoo.com  writes:


In Europe we have been developing and using diesels seriously in
cars far longer than the US has, AFAIK.  Private perceptions and
legislation played their part, as did the clunky performance of
designs back when attitudes were being set in stone.  Add to that
give-away prices of petrol in the US and it's not hard to realise
why diesel became the Sooty Sheep of the fuels-family there.

For many years, in the UK diesel was not taxed as hard as petrol
-- not sure what today's situation is, as I don't run a diesel
and anyhow prices (and taxes) are wandering all over the place.
The famous London black taxis went diesel around when Adam was a
lad, though the pong of diesel and vibration (coupled with urban
taxi driving style) could be stomach-churners for passengers.


That figure is likely to depend on petrol engine type.  You may
be thinking of the commonplace Otto; but (and I mention it purely
as you troubled to mention the Prius in your Subject and posting
list) the Atkinson is more efficient than the Otto, especially if
operated at/near constant speed, and we surely have not heard the
last of oddities like the Stirling.  Add modern control systems.
IOW, study the whole vehicle package when evaluating efficiency.

Previous discussions have wondered whether future hybrid cars may
incorporate diesels, as do some buses currently being trialled in
the UK.  (NB: Google is your friend.)
--
Andrew Stephenson

 
Disclaimer - my experience with diesels is limited to my TDi work truck.

Diesels are still cantankerous - cold starts are problematic; they still
clatter like something's wrong, especially when cold; the diesel guys who
gave me basic instruction warned me to take it easy on the engine until it
warmed up / quieted down. Cars like Mercedes have quiet interiors as a
result of insulation, but outside they still clatter (so my former Euro-car
mechanic partner tells me.) Smoke is a normal part of start-up and warm-up
and smell is a normal part of operation. I canna change the laws of physics.

Turbo diesels are plenty powerful once the turbo gets spun up, but until
then I wish I had four feet so I could hold the accelerator to the floor
with one, feather the clutch with a second, and do the Fred Flintstone thing
with the other two. You haven't experienced turbo lag until you've waited
for 20 psi boost to appear. (I understand VW's variable vane turbo reduces
that quite a bit, but one still has to choose one's gap in traffic
carefully.) Hybrids excel in off-the-line performance. A TDi hybrid, when
the technical details are worked out, would make a dynamite power train.
Even an electrically boosted turbocharger would be an improvement.

Every diesel pump handle I've picked up is a smelly, oily thing. Gasoline
evaporates, diesel accumulates. I always wear gloves while fueling.

Diesels give great economy on the highway, but scarcely better than
conventional gasoline engines in town. Hybrids walk all over them for
in-town economy.

Mike

 
<snip)

This was true of Turbo Diesels but I have found that the modern common rail
diesel engine (of which I have Peugeots HDI model in the 406 that I had new
in 1999) starts better than any petrol engine I have used and is far less
noisy than its predecessors.   Also, unlike petrol engines, there is no drop
off in performance before the engine warms up, it starts and is ready to
give full acceleration straight away.

<snip>

Again, IME, the HDI engine seems not to suffer from any lag and is more akin
to driving a petrol engined car when it comes to pull away and acceleration.
And for interests sake my car averages 46mpg.

--
Keith Willcocks
(If you can't laugh at life, it ain't worth living!)