Re: Hydrogen Production Method Could Bolster Fuel Supplies

From: Mike Swift (tomswift_at_cruzio.com)
Date: 12/14/04 

Date: Mon, 13 Dec 2004 19:00:02 -0800

In article <10rna5mp5l2qo58@corp.supernews.com>,
 "charliew2" <charliew@ev1.net> wrote:

>
> > The rest of the time they're outside their natural efficiency range.
> > Big engines need to be exercised to be efficient. Your big cars are
> > most efficient at pushing air away while travelling at 100mph.
>
> From a wind drag standpoint, engine power requirements rise as the cube of
> the speed. I seriously doubt that Detroit designs engines to be most
> efficient at 100 mph, as this is substantially above the speed limit of
> every state in the U.S.

The limiting factor in engine sizing for cars is to provide power for
acceleration. At speeds of 60-70 MPH (100-120 km/h) most car engines
are running at 25-30% of rated output. If the engine were sized for say
80% of rated output at 80 MPH it would be unmarketable. No body will
buy a car that "can't get out of its own way". Hybrids like the Honda
Insight get around the problem by using the electric motor to give power
for acceleration allowing the small (1000cc) engine to run at a higher
percentage of maximum output for normal running. This is one of the
four methods used to get its 60 mpg.

Mike

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