The Mercedes‐Benz DB‐601A Engine

Abstract

In Fig. 29 are plotted the data obtained during a dynamometer calibration of the DB‐601A engine. The family of curves on the left hand side of the figure gives the sea level power characteristics for various r.p.m. in the operating range, plotted against absolute manifold pressure in inches of mercury. From these curves it will be noted that the automatic boost control takes charge to restrict the manifold pressure to a limiting value of 39 in. of mercury absolute at engine speeds above 1,900 r.p.m. Below 1,900 r.p.m. the full throttle manifold pressure is less than the boost limit established by the automatic regulator. The normal rating of the engine at 2,400 r.p.m. is thus established at 995 horsepower. For take‐off the automatic regulator is overruled by the pilot's throttle for a time interval of one minute established by an automatic clock mechanism, to produce an excess boost in the manifold which, at an engine speed of 2,500 r.p.m., gives the take‐off rating of 1,150 horse‐power at 43·2 in. of mercury absolute manifold pressure. The take‐off power at 2,500 r.p.m. versus absolute manifold pressure characteristics are shown at the upper left hand portion of Fig. 29. The sea level power ratings are somewhat flexible since it is possible to adjust the oil How into the fluid coupling of the supercharger and, by changing the slip, vary the effective impeller ratio. Thus it may be desirable for bomber installations involving take‐off with heavy loads to increase the effective impeller ratio for the maximum boost possible with the quality of fuel available.