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What makes a multifuel a multifuel?

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Badfish740

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One of the reasons I became interested in the M35s was the fact that they used multifuel engines. However, what's not clear to me is what specific characteristics of the engines make them more tolerant of varying viscosities/weights of fuels. Can someone recommend a thread, website, etc...that goes into detail about the injection system of a multifuel? For example, is it direct injection? Indirect? Some hybrid of the two? I'm just trying to learn more about it's capabilities/limitations.
 
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Badfish740

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Recovry4x4 said:
First read this for some spirited discussion!
http://www.steelsoldiers.com/showthread.php?30821-Are-all-Dueces-Multifuel&highlight=multifuel
Then read this. The OP couldn't be convinced by the masses so he reached out to MAN. He was surprised to find out that he was wrong!
http://www.steelsoldiers.com/showth...-from-M-A-N-on-the-Multifuel-Engine&highlight=
Click to expand...
That's exactly what I was looking for-thanks! So it appears that the it's not really the injectors, but rather the combustion chamber/piston design. I did some subsequent searching and found about the "fuel density compensator" as well so I need to so more reading on that. It seems that the multifuels probably employ a fairly conventional injector pump for fuel delivery though, so even though a Deuce can likely burn a variety of fuels, I wonder how said variety of fuels affects the injector pump itself? I've heard reference to adding a certain amount of lubricating oil/diesel/etc...to every gallon of gasoline if gasoline is used as a fuel, presumably to lubricate the pump, so at the other end of the spectrum, I wonder how extremely viscous fuels (WMO/WVO) affect the pump?
 
JasonS

JasonS

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The number one thing that makes it a multifuel is the compression ratio. The MAN combustion chamber is supposedly able to reduce the rate of combustion pressure rise inherent in high compression ratio diesel engines. The FDC uses the fact the the viscosity is proportional to the fuel's energy content to maintain consistent power output. End of story.

Get a copy of Taylor's book on internal combustion engine theory and read up on multifuel engine design. There have been other multifuel engines which did not use the MAN design.
 
Recovry4x4

Recovry4x4

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Another thing about the IP and lube. Unlike most conventional diesels, the multifuel injection pump has an oil line feeding oil to it for lube. Adding lubricity to the fuel is always a good idea but the engineers considered that when they designed this engine.
 
Warthog

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Also read all the simular threads that are listed at the bottom of the page.
 
Warthog

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JasonS said:
I stated the science behind it; most threads have nothing more than speculation thus leading the reader astray.
Click to expand...
Very true. Thank you for your posts. I was just trying to show him that many other people have asked the same question.
 
JasonS

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I want to point out that contrary to the above scan, the Continental multifuel is NOT particularly efficient as diesels go and was bettered by even the mediocre two stroke detroit:

8V92:
0.345 BSFC minimum at 1700 RPM, for an efficiency of roughly 39.8%.
0.355 BSFC at rated horsepower, for an efficiency of roughly 38.7%.

Series-60:
0.311 BSFC minimum at 1550 RPM, for an efficiency of roughly 44.2%.
0.315 BSFC at rated horsepower, for an efficiency of roughly 43.7%.

LDS-465
0.400 BSFC minimum at 2000 RPM, for an efficiency of 34%
0.430 BSFC at maximum horsepower, for an efficiency of 32%

5.9 Cummins VP44
0.334 BSFC minimum at 2000 RPM, for an efficiency of 41.2%
0.365 BSFC at maximum horsepower, for an efficiency of 37.7%
 
iatractor

iatractor

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I enjoyed reading the two main threads that Recovery posted. Got some chuckles out the posts, but overall it was informative. When someone who asks me what makes a multifuel different than a regular diesel engine (to those who are just curious and don't want detailed data), I simply reply it is piston design and compression. That satisfies most curiosity seekers. Most that ask tend to be fascinated with the idea of being able to run a variety of fuel but don't care about the physics and science behind it. Seems like around here there were enough guys who wrenched on the LDT and LDS 465's in the service that they will agree with the short answer.
 
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Badfish740

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I really appreciate all of the replies-I did some creative searching and found that this topic has been beaten to death. However, this thread got to the point a lot quicker than some others. Thanks all. JasonS-where did you find that literature?
 
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JasonS

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Badfish740 said:
I really appreciate all of the replies-I did some creative searching and found that this topic has been beaten to death. However, this thread got to the point a lot quicker than some others. Thanks all. JasonS-where did you find that literature?
Click to expand...
Design and Applications in Diesel Engineering by Sam Haddad and Neil Watson

Principles and Performance in Diesel Engineering by Sam Haddad and Neil Watson

The Internal - Combustion Engine in Theory and Practice by Taylor (often considered the bible of engine design)
 
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