On Feb 13, 11:14*pm, Peter wrote:
WingFlaps wrote

Why should that be? Generally, diesels are great at running at high
power for long periods and they are also *the powerplant of choice for
high reliability when fuel consumption is also an issue (ruling out
turbines) -or am I wrong?

Diesels are indeed great in applications where they can be designed
without weight issues e.g. ships and trucks.

It appears that their problems (Thielert specifically - there is no
other diesel actually flying any meaningful hours at present) are to
do with a lightweight car engine - 1.7 litres - being run at 130HP (or
close to it) for 100% of the time. The original car engine would be
running at 20-30HP, maybe 100HP very briefly in a big Merc on a German
motorway (no speed limits). But an aeroplane is a whole different
situation.


Yes I've heard that argument but I'd like to add/offer a different
POV. What is really stressful for engines is constant power changes
and the temperature fluctuations that involves. Therefore if your
engine can do 150 mph on a german autobahn for an hour or two it
should have no trouble doing it for a 4 hour flight in a plane. I also
agree that marine installations pay no/little attention to weight
(some performance boat installations aim to keep weight low) but tha's
just a design thing. The natural rpm/torque curve for diesels seems to
match a prop better too. The metals exists to make a diesel about the
same weight as a petrol engine so with a bit more hours under their
belt to identify weaknesses I can't see diesels not becoming the (?)
engine of choice (more range, less fuel quality issues). One more
think, no mixture control just rpm and pitch!
Imagine just setting rpm just one and then doing everything else with
pitch ;-) ...

Cheers