Another New Daimler-Benz Diesel
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FOLLOWING our exclusive announcement last week about the DaimlerBenz OM 346 direct-injection diesel engine, a 10.8-litre six-cylinder unit with an output of 210 b.h.p. (DIN) at 2,200 r.p.m. (when equipped with viscous fan drive), Daimler-Benz A.G. announces another new direct-injection unit this week. It is the OM 352, which replaces the OM 322 indirect-injection design, and is a 5.675-litre six-cylinder engine with a DIN output of 126 b.h.p. at 2,800 r.p.m. This figure is the same as that quoted for the OM 322, which was a 5-675-litre engine also, but the new engine's maximum torque of 260 lb. ft. at 1,600 r.p.m. is 10 lb. ft. greater. The combustion principle employed in the OM 352 is along the same lines as that used in the OM 346, but there are certain mechanical differences between the two engines. For instance, the smaller unit has a single cylinder head, and there are only two valves per cylinder. The light-alloy forged pistons carry five rings in all, there being one chromium-plated and two normal compression rings, plus a chromium-plated 'oil-control ring above the gudgeon pin, and a second oil-control ring immediately below the pin. The b.m.e.p. at 1,600 r.p.m. is 113.8 p.s.i., compared with 119-47 p.s.i. for the OM 346, and the injection pressure is slightly higher, at 2,844 p.s.i. The engine has a compression ratio of 17 to 1, whereas the unit it replaces had a compression ratio of 23 to I. Its power-to-weight ratio is 7.16 lb./b.h.p.