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Direct personal experience with diesels has shown me that high compression is one key, and good atomization another. NON TURBO engines with very high compression ratio, and undersize injector tips beat everything else. Turbos are designed to achieve higher power, and of course must be used with a lower compression ratio to stay within limits. Unfortunately boost is proportional to how much power you are pulling out of the engine, so we run a pretty low boost when loafing down the highway at low throttle........where we measure mileage. The turbo inherently robs power due to back pressure, and it adds complexity to the system. You want max efficiency....... us a non-turbo engine. Small injector tips result in far smaller droplet size for a given fuel flow than large tips......... This is very significant. With diesels, power mods work against efficiency as a rule. I once set out to build the most efficient diesel I could to run a pump feeding a 1/4 mile wheel line sprinkler. The resulting unit burns about half what any other diesel running the same load does. It involved a lot of research to achieve the most efficient pump for the job to begin with....... About $3000+. It had to be matched to the engine RPM and horsepower. The engine was an Isuzu Thermo King unit from a truck reefer. Rated at 18 HP in that configuration, it is also used in Isuzu pickups at about 50 HP. I left the small pump and injectors on it.........but had them rebuilt, and had the pump stroked out to max, which with the small pump delivered enough fuel for about 35 HP......... At full power, the injectors are operating well beyond design capacity, but you only operate at that horsepower while filling the lines. Operating load is about 22 HP, and the engine burns .7 gallons per hour, or a little less than 17 gallons per 24 hrs.
These things have been known since the 20's.......... I have a book from about 1930. Diesel Engines by Von Bongart that goes into great detail, studies injection systems, compression ratio, chamber design, etc..........The principles outlined in it guided the entire project, and the results very much confirmed the principles. The engine is now approaching 20,000 hours total on the Hobbs meter, and still pumps water with the same level of efficiency!!
Howard
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