Well-proven technology for the crankcase and cylinder head

A crankcase of grey cast iron provides the solid basis for the new-generation diesel engines of the A-Class. In view of the compact engine dimensions, increased displacement and higher ignition pressure this well-proven material offers the most advantages. While maintaining the distance between cylinders, Mercedes engineers have increased the bore from 80 to 83 millimetres and the stroke from 84 to 92 millimetres. The forged connecting rods have been lengthened to 147.85 millimetres. The crankshaft is likewise of forged steel and features five bearings, eight counterweights and a vibration damper. The pistons, whose crowns have a special, dished profile, are equipped with cooling ducts into which oil is sprayed by pressure-controlled nozzles.

The cylinder head in the new diesel engines has two overhead camshafts, each of which controls two intake and two exhaust valves via roller-type rocker arms. The steel camshafts are produced using an internal high-pressure forming process developed by Mercedes-Benz, which ensures a very high level of precision: the cavities in the blanks are filled with a liquid and subsequently formed for a precise fit at a pressure of up to 2000 bar. A chain drives the camshaft on the intake side, which meshes with its counterpart on the exhaust side.