I've spent many enjoyable hours over the past year or two reading the
archives of TWL.  I don't have a boat, but love reading the discussions
here.  I do have some shadetree experience with the Cummins B series (12
valve 6BT and the newer 24 valve ISB) as used in Dodge trucks.

I've noticed that every once in awhile a discussion of turbos
surfaces--usually whether it's more cost-effective to remove them and run
naturally-aspirated.  The idea that the turbo could burn itself out, or be
damaged in any way by running it lightly loaded absolutely astounded me.
In truck applications we're only concerned with hot shutdowns and
"barking" the turbo (rapidly going from full-throttle to no-throttle
while at high boost--the 20 or 30 psi air in the intake manifold is no
longer being accepted by the engine at nearly the same rate and takes the
path of least resistance, which is back out the way it came.  This results
in massive stresses on the turbo since it wants to spin the compressor
backwards).

It really seems to me that the size of the exhaust housing would be
critical in how the turbo behaves at different engine loads.  A great
example would be contrasting the engines in my 1992 Dodge truck vs. my
2000 truck.  The 1992 truck came with a Holset turbo with a 21 square
centimeter, non-wastegated exhaust housing, while the 2000 has a 12 sq.
cm. wastegated housing.  The 2000 truck, with its small wastegated housing
develops boost at much lower throttle/load.  The 1992 with it's very large
exhaust housing is a bit more at home at high load/full-throttle usage vs.
light load where it can't develop much boost.  Last month someone touched
on wastegates, which I believe would be part of it.  Wastegates help
relieve the exhaust restriction of a smaller housing--but you still need
the smaller housing size to get boost at lower engine loads.

Since I tend to drive the 1992 truck empty, I recently replaced the 21 sq.
cm.  housing with a smaller 16 sq. cm. housing.  Low-load boost is up
noticeably, and exhaust gas temps at high load are not significantly
impacted.  This makes me strongly suspect that something similar might be
an option in the marine environment.  Unfortunately I've never seen what
boost and EGT numbers are typical at various loads in trawlers.  I also
have no idea what exhaust housing sizes are typical on diesels in marine
applications, so I have no real frame of reference to determine how
beneficial, if at all, a housing swap would be (and of course, every boat
and engine is different).  But it seems to me that the basic concept
should work in the marine environment just as it does in the light/medium
duty truck environment.  Either that, or I'm completely missing something,
in which case please go easy on me!  :-)

What do you all think?

Mike

I wonder how long it will take before these will be readily available to
yachtsmen?

http://www.skysails.info/index.php?id=13

For those doing some serious cruising, the cost/benefit ratio might make the
outlay for something like this recoverable in just 2 years or less, although
I'm still waiting to hear what the developers estimate the cost of such a
system for an 85 to 100 footer might be.

I've already "volunteered" to perform a TRANSAT and conduct real world
testing in consideration of the installation of one of their systems.

Further details when and if I hear back from them, film at 11.

Regards,

James

(snip)
Egads, a spinnaker for motor vessels.
Just wait until the first knockdown in a squall.
(endsnip)

Heh heh . . . I consider it an emergency escape vehicle . . .
Hmmm . . .
Lessee,
Shafts exited the boat (to save it?) (see shaft coupling thread). Check.
Boat sinking. Check.
Rope cinched around waist, check.
35+ knots of wind, check.
REALLY big kite (hugely giganticus kiteus!), check.
Rope cutters, check.

WoooHooooooooooooo!!!

CUAgain,
Daniel Meyer
http://cuagain.manilasites.com