David:
There are a lot of myths floating around regarding the Multifuel engine. I
will try to help you.
In the late 1950's the decision was made to adapt the G742 series vehicles
(as well as many other tactical vehicles) to run on diesel or gasoline or
various other fuels. Fitting the Continental LDS-427 turbosupercharged,
multifuel engine did this. This engine built under license from M.A.N.
(Maschinenfabrik Augsburg-Nurnberg) uses the Hypercycle combustion process.
Into the top of the piston of this engine is machined a spherical combustion
chamber. During operation the injector sprays 95% of its charge onto the wall
of this chamber in the form of a thin film. The remaining 5% is atomized.
The compression stroke, which generates temperatures in the 900-1000 degree
range, ignites this atomized charge, and the main portion of the charge is
gradually vaporized by an air swirl created during the intake and compression
strokes. Since the air swirl removes only the top surface of the fuel
sprayed on the walls of this combustion chamber during the power stroke
combustion is even and there is no detonation knock.
Unfortunately, the LDS-427 was not entirely successful, and this led to the
development of the LD-465 series of engines. Whereas the LDS-427 was
turbo-supercharged, the LD-465 was a naturally aspirated engine. If you ever
convoy behind someone driving a truck with one of these engines it is a
memorable experience, as there is a voluminous cloud of black smoke at
virtually all speeds. It is this smoke cloud that led to the development of
the LDT-465-1.
While the LDS-465 version of this engine was from the beginning
turbosupercharged (as well as other internal changes) for additional power
and used in 5-ton trucks, the turbosupercharger on the LDT was applied to
reduce this exhaust plume. The LDT-465 produces only 4 horsepower more than
the LD-465, but the power comes on quicker, and the exhaust plume is not as
pronounced.
At this point I will mention that I have seen it said in various books and
articles that the LDS-427 were multifuel engines, but the LDT-465 series were
not multifuel engines. I have not been able to find any information to
support these statements. The nameplate on the engines say "Multifuel," both
series were produced under the M.A.N. license, the Technical Manuals all say
"multifuel," and the block, head, and piston designs are essentially the
same. Therefore I believe both the LDS-427 and LDT-465 series to be
Multifuel engines.
The injection pumps on all of these engines except the early LDS-427 were
originally equipped with a fuel density compensator, which varies the fuel
delivery rate as fuels are changed or mixed. As built, no adjustments are
changes are necessary to change fuels, and mixing of various fuels is
permissible.
In recent years, the fuel density compensators have been bypassed, and they
are now tagged "diesel fuel only," but instructions are included to reconnect
the compensator.
In practical terms, it is generally considered unwise to operate these
engines on gasoline, and under no circumstances is av-gas permitted.
I have burned diesel, kerosene, and Jet A in my trucks at various times, and
can note no difference in engine or vehicle performance.
Hope this helps,
David Doyle
This archive was generated by hypermail 2b29 : Mon Feb 05 2001 - 07:13:44 PST