Diesel for Diamond DA40?

"Greg Copeland" wrote

On top of all that, the energy density for 100LL is some
20% higher (IIRC; or was it 40%) which means fuel consumption is 20%
higher for the same HP rating.

I think you have that backwards. Diesel fuel has a higher energy density
than 100LL. You burn less fuel per HP produced.
--
Jim in NC

Morgans wrote:
"Greg Copeland" wrote

On top of all that, the energy density for 100LL is some
20% higher (IIRC; or was it 40%) which means fuel consumption is 20%
higher for the same HP rating.

I think you have that backwards. Diesel fuel has a higher energy
density than 100LL. You burn less fuel per HP produced.

actually the energy density by weight is about the same. However Diesel is
about 0.85 kg/litre, while Gasoline is 0.725 kg/l. So the energy content per
volume per litre/gallon is higher for diesel.

However the important point here is the efficiency of the engine, Diesels
do about 15-30% better. So from the same weight of fuel a Diesel will get up
to 30% more energy to the prop. While most diesel engines are indeed a
slight bit heavier than gasoline engines of similar power output, the weight
of a diesel engine plus fuel for any decent range is less than with
gasoline, hence useful payload is better.

If gross weight is not an issue but fuel tank capacity, a diesel will
extend your range through better efficiency AND the higher energy content
per volume.

And of course there is the price issue, in Europe Diesel (or Jetfuel) is
significantly cheaper than Avgas. Some Thielert operators claim a reduction
in overall fuel cost, fuel price times fuel consumption, of up to 2/3 vs.
Avgas.

If I was shopping for a new engine (or a new plane with new engine) I would
go for a diesel.

regards,
Friedrich