Dave Plowman (News) wrote:
In article ,
The Natural Philosopher wrote:
The trouble is electric car makers and their advocates always quote
the best possible range and best possible performance without making
it clear the two can't happen at the same time. To fool the gullible
like dribble, who already thinks it's possible to exceed 100%
efficiency. Now we all know that driving an IC car hard results in
heavier fuel consumption and of course the same applies to an electric
one.

But thats no different from any other car. My Jag I have just sold was
quoted as 0-60 in 5.2 secs and 22mpg.

There are official fuel consumption figures for any IC car which will give
some guidance between makes - but not for electric ones. And hybrids
distort the issue since the town figure is so much better, leading people
to think they are more economical for all use. Which leaves advertisers
open to claim what they want for electric vehicles

It CERTAINLY would NOT do 22mpg at its rated top speed of 156mph.

Around London, it used to be about 12mpg. Over 70mph it dropped to
20mpg, and over 100mph it was around 17mpg.

Those figures are very poor - but it is a design dating from the '60s and
far too heavy with poor CD so the only way to get decent performance was
with vastly powerful engines.

No, its just an utterly over engined car - 4 liter superharged with an
auto box.

Design from the 90's actually :-)

And built for luxury, not fuel consumption.


Make an electric car weighing that amount
etc for a reasonable comparison. Because such things *always* cloud the
issue. Electric cars will be made with every weight saving and friction
reducing trick in the book. And then compared to the worst possible
conventional IC engined vehicle, when of course the comparison should be
with a similarly advanced construction one. It's called common goalposts.
;-)


Typical figures suggest that a small equivalent 100bhp 5 door town car -
something like a Fiesta..is replicable with about 50Kwh for 200 miles range.

At 50mph average, an average drain of 12.5kw. About 16.7bhp.

If one thinks it might do 6 times that power to do 120mph continuously,
then its got 20 minutes 'in the tank' - or about 67 miles 'in the tank'
One third of the fuel consumption. I think that is probably about right.

I think that is very reasonable. Anyone who has actually really stirred
a car around knows that at the best, you can use full power about 70% of
the time, the rest is braking for the next corner..unless you have a car
geared to achieve max power at max speed and hit the autobahn..

One of the major reasons that diesels are so mpg efficient is that they
are most efficient at low throttle settings...petrol tends to be far
less so.