Roger,

What you were told is substantially correct. (I would just love to close
there, but it would not be either fair or educational.)

If you just read the post of moments ago, remember that the typical
torque curve of a mechanical fuel pump diesel is flat below the torque
peak (misnomer in much of the diesel community note to follow.)

Most diesels are not quite a flat torque curve because the design had
been optomised one way or the other. They are often so flat that the
overload (as you describe) will cause the engine to keep losing rev
until it the load it is carrying drops or the engine stalls.

BUT - (you just knew that was coming)

The BIG exception here is that the fuel control governor in many truck
engines causes the engine to de-fuel with increasing rev to create what
is called "torque backup" a feature that will allow the truck to slow on
hills with out stalling - this allows a hugh reduction in gear shift
work for the driver.

Promissed note: For many over the road engines designed with torque
backup, the published torque peak is not the actual peak, but the knee
in the torque curve where the governor starts defueling based on speed
to limit the smoke.

Did I say that all well enough so you can ask a question if you have one?

Matt Colie
derbyrm wrote:

Matt,

In line with this discussion, maybe you can affirm/clarify a squirmy factoid
from my past (ca 1975). We were simulating the electrical distribution
system for a DDE class of ships and I was told that: when you overload a
gasoline engine, it lugs down, complains, and lets you do something about
it. In contrast, when you overload a diesel (such as the ones that drove
two of the generators) it just quits. (The simulation was to train
operators and condition them to shed the load before the engine quit; among
other things.)

Thanks,
Roger

http://home.insightbb.com/~derbyrm

"Matt Colie" wrote in message
...

Skip,
As an engine professional for many decades I can tell you that all you
need is the two published numbers I hope are in the engines
specifications.
That would be the torque peak and speed and the horsepower peak and speed.
For a naturally aspirated diesel this is very close to what a dyno test
would give you.
Turn the HP back into torque (rev*tor/5252=hp)_ and plot it out as two
straight lines (it isn't, but it won't matter much). If I can find it and
you are interested, I could try to post the one page explaination of this.
Ta Da - power curve

Matt Colie - still trying to get out of Detroit and back to tidal water
after 30+ years.


Skip Gundlach wrote:

Hi, y'all...


Back on the boat and about to pull the shaft and tranny to true the
shaft and plates and, perhaps, redo the MaxProp settings.

However, before I can do the calculations, though I have the pdf of
both the parts and manuals, I can't find anything about the power
curve.

Does anyone have them/know what they are, and willing to share?

Thanks.

L8R

Skip, on the boat for the duration, very small breaks excluded

Morgan 461 #2
SV Flying Pig KI4MPC
http://tinyurl.com/384p2 The vessel as Tehamana, as we bought her

"Believe me, my young friend, there is *nothing*-absolutely
nothing-half so
much worth doing as simply messing, messing-about-in-boats; messing
about in
boats-or *with* boats.
In or out of 'em, it doesn't matter. Nothing seems really to matter,
that's
the charm of it.
Whether you get away, or whether you don't; whether you arrive at your
destination or whether you reach somewhere else, or whether you never
get
anywhere at all, you're always busy, and you never do anything in
particular; and when you've done it there's always something else to
do, and you can do it if you like, but you'd much better not."