The liter designation is a metric measurement of engine displacement....size of the engine internals. A liter is about 60 cubic inches for all practical uses. Therefore, a 3 liter engine would be about 180 cubic inches. A five liter engine is 300....or, in ford speak, is called a 302. The old 6.9 liter Benz engine is about 413 cubic inches.........same as the old Chrysler's powerhouses of the muscle car days. Now, the power derived from each liter or cubic inch varies greatly. A good running gasser is about one horsepower per cubic inch or 60 h.p. per liter. Honda has their sports version engines up to about 100-115 horse power per liter--this used to be formula one territory! If the gasser engine is supercharged in some fashion, the power derived is much greater....old formula one engines (72 cu. in.) used to provide up to 1100 h.p. via extra fuel and boost. All a supercharger does is "grow" the engine size by makeing it able to burn extra fuel for power.
In diesel engines, the horsepower derived is much lower than gas engines, but the torque is usually higher.

Regards

Run-em
1983 300 SD..aka..SPARKY THE DIESEL