> >> As far as weight, my Dodge Ram has the Cummins diesel, the engine
 > >> weighs 1,000 lbs., give or take
 > >> a couple.
 > >>
 > >> As for fuel economy, Dodge does not make a gas engine that will touch
 > >> this diesel.  I consistantly
 > >> get 21+ mpg at highway speeds of 70 to 75 mph.  This is a 3/4 ton quad
 > >> cab truck.
 > >>
 > >> Just my $.02.
 > >>
 > >> Steve -in Michigan
 > Yes, but what is the mileage per pound of fuel?
 >
 > Chris C.
 > microcosman.com/aircraft

Diesels do extremely well in automotive service and that includes empty
pick up trucks as the cruise HP is down around 20%. This is because diesels
will run extremely lean at low power. The throttle (there is none) is
always wide open
and only enough fuel is injected to generate the low power required.  As
the HP increases towards 100% the fuel burn of the diesel and the gasoline
engine is much much closer. This is the case in aircraft engines.

According to Peter Garrison in his recent article in Flying magazine
the Renault aircraft diesel engine weighed 100 pounds more and burned
only one gallon less per hour. 25% more engine weight for 10% less fuel.
It only makes sense in Europe where the tax on diesel fuel is half
of what it is on gasoline.

Paul Lamar

dave wrote:

Here's what I was getting at: Put the highest compression rotors in the
engine you can get. Is that about 13:1 ? Then, turbo charge it to about
46mm of MP. That should give you combustion pressures high enough to
sustain direction injection of diesel fuel. As the efficiency of
 diesels is due to higher compression ratio and the fact that at any
power setting, they are always running lean to extremely lean, you get
fuel savings and the ability to burn Jet-A if needed.

Q: Can the 13B or 20B (if I can ever find a 20B) handle these pressures?
-dave

Forget it. The highest compression ratio you will ever be likely to see in
a rotary is 10:1. Anything beyond that and the depression in
the rotor become so shallow the combustion chamber becomes near useless.

Just use a spark plug or a glow plug out of a Mercedes diesel to heat
the combustion chamber. The draw back to the glow plug is it draws
electrical power all the time. The spark on the other hand
only happens when needed.

Paul Lamar
 
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