Cylinder Block Layout and Design Decisions

Abstract

In Chap. 5 the required engine displacement was calculated, and in Chap. 6 the number of cylinders, cylinder layout, and bore-to-stroke ratio were determined. These earlier decisions form the starting point for the discussion of this chapter. It is in this chapter more than any other that it will be necessary to limit the discussion to designs specific to automotive applications. Over the entire range of reciprocating piston internal combustion engines there is an extremely wide range of cylinder configurations and block layout and construction techniques. By limiting the discussion to automobile engines and heavy-duty engines in mobile installations, primary attention will be placed on in-line four, five and six cylinder engines, and vee six, eight, ten, and twelve cylinder engines. Casting the net a bit wider allows discussion of horizontally opposed four, six, and eight cylinder engines, and mention of the recently revived ‘W-8’ and ‘W-12’. The cylinder block is the foundation of the engine, and supports the piston, cranktrain, cylinder head, and sometimes the valvetrain. It also houses the lubrication and cooling systems. It provides mounting points for the charging system, starting system, power take off (PTO), and typically has mounts which support the entire powertrain. The engine may be rigidly mounted as a structural member of the chassis, such as in a racecar or motorcycle. The cylinder block supports a variety of static, dynamic, and thermal loads, and must provide stiffness and alignment for many components. Because of the complexity of geometry, and complexity of loading, hand calculations are rarely used. Simplified finite element analysis (FEA) of a single power cylinder is usually the starting point, prior to analysis of the entire assembly.