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#3066278 - 07/15/13 04:54 PM Re: Duece and a half [Re: ridgerunner]
2cool Offline


Registered: 07/13/11
Posts: 451
Loc: Delaware
The engines in the olde Truck, 2 1/2 ton, 6X6, M-48, were compression-ignition engines designed by M.A.N. (Machinen fabrik von Augusburg und Nuernberg) built under license for the Army by Mack, Continental, White, and Hercules. The pump was a Bosch single piston distributor type, where the fuel lines from the pump to the injectors looked for all the world like reallly long spark plug cables. As the fuel entered the pump, it went through the Fuel Density Compensator. The density of the fuel would cause an adjustment of the quantity of the fuel injected, and change the injection timing. The theory was that the denser the fuel, the more energy. The denser the fuel, the more time it would take to burn.

IIRC, the Technical Manual called for 1 Qt. SAE 10 oil per 10 gallons of gasoline, just to lube the pump. It would get much lower mileage on gas, but it would go. I believe that even with a turbo, the output was 130 hp. But then the Army only planned on it going 35 mph in line-haul style operations.

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#3358955 - 05/01/14 02:42 PM Re: Duece and a half [Re: ridgerunner]
ironman_gq Offline


Registered: 04/30/14
Posts: 136
Loc: MN
The old ones would run on just about anything because the injection systems were a lot more robust and simple. The old injectors were just a poppet valve with a nozzle on one side, it fired once per compression cycle and didn't need to be too terribly precise in metering fuel. Same with the pumps, they ran at a couple thousand psi at most, The new fuel systems on these trucks are using electronically fired injectors that can fire 4-5 times per cycle and pumps that operate at 30 thousand psi. To do that everything must have very precise tolerances, a change in fuel viscosity or a little debris in the fuel and the whole thing falls apart and parts get damaged.

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