subaru diesel

wrote in message ...
On Mar 22, 9:33 pm, "Dale Scroggins"
wrote:
"Blueskies" wrote in message

...



"Morgans" wrote in message
...

"Philippe Vessaire" wrote in message
news:19459447.yEvPs9oxTh@GastonCoute...
Hello

Torque curve page 6

http://www.subaru.fr/special/pdf/doc...esel_lo_08.pdf

Holy crap! That thing has the peak torque, and it is almost a level
line, from about 1600 rpm to about 2400 rpm!

That sucker should really pull a big prop, and well!
--
Jim in NC

Is the price of diesel fuel 25% above gasoline prices everywhere?
Jet A costs the same as 100LL now also, so what is the benefit?

SNIP
2. No ignition system needed.

Not to be a ball-buster, but the injection systems for the new
generation of diesels is incredibly fancy. From a risk analysis
standpoint, it is hard to say whether this system in place of magnetos
is a gain or a loss.

3. Turbocharging a diesel is a win-win proposition. EGT is lower, so turbo
system parts last as long as the engine, usually. Turbocharging improves
both performance and fuel efficiency (not always true for gassers).

True, but boost levels in diesels inversely effect their reputation
for reliability.

SNIP

8. I can make biodiesel for 67 cents a gallon. You or I can buy off-road
diesel or heating oil for much less than either auto gas, avgas or jet A.

Biodiesel gels at a higher temp than does winter diesel, and be damned
sure you have no rubber in the fuel system. And the 67 cents is
quoted for recycled oil. Not my first pick at altitude.

9. For a given trip, less fuel is needed, both in volume and weight. 25%
to 35%, depending on the trip profile. If the diesel is turbocharged and
gasser is not, the diesel's ability to cruise significantly higher may
result in a bigger efficiency spread.

This is dependent on tuning the boost map, and whether the blower is
big enough. Off the shelf this may or may not be true. I have not read
flight tests for any new European diesels which have been impressive
in high altitude performance. I doubt this is because of any
fundemental flaws, but rather performance tuning.

10. Props are more efficient at lower RPMs, usually. Diesels have torque
to turn props slow in cruise, like a turboprop (1800-1900 RPM), giving maybe
another 5% efficiency gain, and a quieter cabin to boot.

Given time, I can think of more. Please note that gas engines were
abandoned decades, nay, scores of years ago in other transportation sectors.
It will be the same in aviation if the weight difference shrinks enough.

DS

I dig your enthusiasm. Please post if you hear of any new diesel/
biodiesel aviation projects. I would be interested in reading any
related results. I believe that the new generation of diesels are the
long term solution for keeping GA operating costs down. But it will
take a while.

-Matt


Why any sort of reciprocating engine?...small turboprops would be the best solution of they can get the mass fuel flow
problems resolved...

"Dale Scroggins" wrote in message
...

...
1. Most diesels wear more slowly than gas engines. The fuel is a better
lubricant than gasoline is, and the combustion products are a bit more
benign.

Except, of course, for the particulates. Particulates are hell on bearings,
and lungs, and...
NOx tends to run higher and isn't usually clasified as "benign"

5. Automatic mixture control.

"mixture control is irrelevent" would be a more accurate statement.

7. Lower fire risks.

Not really.

10. Props are more efficient at lower RPMs, usually. Diesels have torque
to turn props slow in cruise, like a turboprop (1800-1900 RPM), giving
maybe another 5% efficiency gain, and a quieter cabin to boot.

Depends on how the engine was designed, not how the fuel is ignited.


Given time, I can think of more. Please note that gas engines were
abandoned decades, nay, scores of years ago in other transportation
sectors. It will be the same in aviation if the weight difference shrinks
enough.


Well, there's the problem, isn't it. Making a light weight diesel that will
last.

Note: I'm not suggesting that diesels are a bad idea - they do have there
advantages. But, let's not over sell...

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
When immigration is outlawed, only outlaws will immigrate.

"Capt. Geoffrey Thorpe" The Sea Hawk At Wow Way D0t C0m wrote in message
news:N6adnXfOAtwpgHXanZ2dnUVZ_sWdnZ2d@wideopenwest .com...
"Dale Scroggins" wrote in message
...

...
1. Most diesels wear more slowly than gas engines. The fuel is a better
lubricant than gasoline is, and the combustion products are a bit more
benign.

Except, of course, for the particulates. Particulates are hell on
bearings, and lungs, and...
NOx tends to run higher and isn't usually clasified as "benign"

The specific comparison I had in mind was a current-production piston
aircraft engine burning 100LL, compared to a current-production automotive
diesel engine. Given a choice of the lead compounds that collect within and
are emitted by the gasser, and the low levels of particulates deposited and
emitted by a current-production automotive diesel, I'd prefer the
particulates.

As to oxides of nitrogen, given that current production gas aviation engines
run with advanced ignition timing, have no EGR, and operate at elevated EGT
most of the time, I doubt a current production auto diesel would produce
more NOx, and would likely produce less. I'm open to numbers, if you have
them.

Again, my comparison was between current diesels and current gas aircraft
engines, not current automotive gas engines.


5. Automatic mixture control.

"mixture control is irrelevent" would be a more accurate statement.

For a turbodiesel, "automatic mixture control" is a more accurate statement.
Mixture control is quite relevent, and automatically managed.


7. Lower fire risks.

Not really.

Hmm. So the dozens of induction fires (some of which caused substantial
damage) that I've witnessed over the years are just as likely with a diesel
engine? And all the extra precautions we followed over the years when
fueling and defueling avgas (or mogas), compared to jetA, were a waste of
time?


10. Props are more efficient at lower RPMs, usually. Diesels have
torque to turn props slow in cruise, like a turboprop (1800-1900 RPM),
giving maybe another 5% efficiency gain, and a quieter cabin to boot.

Depends on how the engine was designed, not how the fuel is ignited.

Hmm again. So the burn characteristics of the fuel, the ability to inject
additional fuel after initiation of combustion, and the surplus of available
oxygen have no impact on engine torque curves?



Given time, I can think of more. Please note that gas engines were
abandoned decades, nay, scores of years ago in other transportation
sectors. It will be the same in aviation if the weight difference shrinks
enough.


Well, there's the problem, isn't it. Making a light weight diesel that
will last.

Note: I'm not suggesting that diesels are a bad idea - they do have there
advantages. But, let's not over sell...

Wasn't the prospect of a relatively light weight diesel available to
homebuilders the point of this thread? No one knows if Subaru's diesel will
match the durability of a current-production avgas engine. However, newer
diesel injection methods have helped reduce internal engine forces, so
durable, light diesel engines are on the horizon.

What do you see as the advantages of diesel aircraft engines?

DS

On Fri, 21 Mar 2008 22:06:30 -0400, "Morgans"
wrote:


"Philippe Vessaire" wrote in message
news:19459447.yEvPs9oxTh@GastonCoute...
Hello

Torque curve page 6

http://www.subaru.fr/special/pdf/doc...esel_lo_08.pdf


Holy crap! That thing has the peak torque, and it is almost a level line,
from about 1600 rpm to about 2400 rpm!

That sucker should really pull a big prop, and well!

Like I said!

--
Posted via a free Usenet account from http://www.teranews.com

clare at snyder dot ontario dot canada wrote:

Torque curve page 6

http://www.subaru.fr/special/pdf/doc...esel_lo_08.pdf

Holy crap! That thing has the peak torque, and it is almost a level
line, from about 1600 rpm to about 2400 rpm!

That sucker should really pull a big prop, and well!

Like I said!

At 2400 rpm, you only got 90KW or 120Hp, not enough for a 400lb
engine.

Remember: power matter for flight.....


By
--
Volem rien foutre al païs!
Philippe Vessaire Ò¿Ó¬