Diamond DA-40 with G-1000 pirep

George Patterson wrote:
Do a comparison of the diesel and gas Maules. The diesel costs more,
True.

is slower (due to cooling drag),
It may be slower, but it doesn't "ring true" to me that the cause is higher
cooling drag. Diesel engines are more efficient than gasoline engines
because they extract more of the chemical energy as useful work, and less
chemical energy is converted to waste heat. With less waste heat, their
cooling drag should be *less* than a gasoline engine's.

and carries less weight (the engine weighs more).
True.

Russell Kent

Russell Kent wrote:

It may be slower, but it doesn't "ring true" to me that the cause is higher
cooling drag. Diesel engines are more efficient than gasoline engines
because they extract more of the chemical energy as useful work, and less
chemical energy is converted to waste heat. With less waste heat, their
cooling drag should be *less* than a gasoline engine's.

Well, they don't. They have a higher compression ratio, and that produces heat. The
SMA diesel is air-cooled, it produces more waste heat than an IO-540, and there's
more cooling drag than with an IO-540.

George Patterson
In Idaho, tossing a rattlesnake into a crowded room is felony assault.
In Tennessee, it's evangelism.

"G.R. Patterson III" wrote in message
...


Russell Kent wrote:

It may be slower, but it doesn't "ring true" to me that the cause is
higher
cooling drag. Diesel engines are more efficient than gasoline engines
because they extract more of the chemical energy as useful work, and
less
chemical energy is converted to waste heat. With less waste heat, their
cooling drag should be *less* than a gasoline engine's.

Well, they don't. They have a higher compression ratio, and that produces
heat. The
SMA diesel is air-cooled, it produces more waste heat than an IO-540, and
there's
more cooling drag than with an IO-540.

Aren't they also heavier, i.e., pound of engine weight per HP generated?

Tom Sixkiller wrote:

Aren't they also heavier, i.e., pound of engine weight per HP generated?

Every one of which I've read is heavier than an equivalent gas engine, especially
with all the accessories installed. Since some of the new diesel designs are
2-stroke, and most gas engines are 4-stroke, though, some of the newer ones may
actually come in lighter than the equivalent gasoline engine (if they ever make it to
production).

George Patterson
In Idaho, tossing a rattlesnake into a crowded room is felony assault.
In Tennessee, it's evangelism.

G.R. Patterson III wrote:

Aren't they also heavier, i.e., pound of engine weight per HP generated?

Every one of which I've read is heavier than an equivalent gas engine, especially
with all the accessories installed. Since some of the new diesel designs are
2-stroke, and most gas engines are 4-stroke, though, some of the newer ones may
actually come in lighter than the equivalent gasoline engine (if they ever make it to
production).

Help me out here.

Why "especially with all the accessories installed"?

Why is a 2-stroke cycle engine lighter than a 4-stroke?

Thanks.

Dave

Dave Butler wrote:

Why "especially with all the accessories installed"?

The injection system tends to be more complex and heavier than gasoline models or
carburettors. This is because the injectors spray fuel directly into the cylinder
rather than into a section of the intake manifold. Many diesels handle the higher
CHTs by using water cooling systems, and those add weight (Lycoming was working on
one of these a few years ago). On the other hand, the glow plug systems used for
starting tend to be lighter than the magnetos used in gas engines.

The main cause of the weight difference is still the fact that everything must be
beefed up to handle the higher compression, though.

Why is a 2-stroke cycle engine lighter than a 4-stroke?

There are twice as many power pulses per minute with a 2-stroke. They usually are not
as efficient as a 4-stroke, so you don't get twice as much power, but they will
easily produce 1.6 times the power of a 4-stroke the same size, and most do better
than that. So a 200hp 2-stroke engine is smaller than a 200hp 4-stroke engine. In
addition, 2-strokes don't have a valve train, which saves some weight.

George Patterson
In Idaho, tossing a rattlesnake into a crowded room is felony assault.
In Tennessee, it's evangelism.

Why "especially with all the accessories installed"?

-heavier high-pressure fuel pumps, lines etc which are not needed on gas
engines.
-on two strokes you need a supercharger to get them started.

Why is a 2-stroke cycle engine lighter than a 4-stroke?
-less stuff: with twice the power strokes per piston, one needs fewer
pistons and all associated stuff. For example the three cylinder Wilksch is
as smooth as a six cyl gas engine http://www.wilksch.com/

If only they could be lighter :-)

Cheers & blue skies,

Pete

Europa Builder A239 dual-wing

http://europa.zutrasoft.com



"Dave Butler" wrote in message
...
G.R. Patterson III wrote:

Aren't they also heavier, i.e., pound of engine weight per HP generated?

Every one of which I've read is heavier than an equivalent gas engine,
especially
with all the accessories installed. Since some of the new diesel designs
are
2-stroke, and most gas engines are 4-stroke, though, some of the newer
ones may
actually come in lighter than the equivalent gasoline engine (if they
ever make it to
production).

Help me out here.

Why "especially with all the accessories installed"?

Why is a 2-stroke cycle engine lighter than a 4-stroke?

Thanks.

Dave

G.R.,

. Since some of the new diesel designs are
2-stroke, and most gas engines are 4-stroke,


None of those certified or close to certification are 2-stroke. And all
the Thielert engines are very close to the Avgas engines they replace,
weightwise.

--
Thomas Borchert (EDDH)