Circuit block and cylinder heads and upper crankcase must accept the forces that are changing and significant, in addition, these parts are exposed to known stresses that occur due to uneven thermal expansion. With all this must not become deformed blocks in which the moving elements of the piston mechanism. The rigidity of the block and cylinder heads and upper crankcase is therefore of utmost importance.
The mass of the block and upper crankcase fast-running engine is approximately 25% to 37%, a mass of cylinders from 8% to 13% of the total weight of the engine. Since motor vehicles intended for the search to the smaller mass, because inertia of the vehicle, cost and convenience for installation.Just a light and rigid performance is achieved in the following ways:
- Using materials with low density, such as aluminum alloys;
- Purposeful performance fins that provides the necessary strength and rigidity, with a reduced wall thickness;- Suitable accommodation dividing plane crank case and lighter at the same time as performing lower body, which is usually unloaded;
- Using a larger number of main bearing crankshaft, which minimizes sporadic strains in materials and lightweight design allows the upper crankcase and crankshaft.From fast-running engine also requires a minimum built-in volume. The built-in volume have a major impact dimensions of the cylinder block and crankcase.
To these parts of the occupied less space, the distance between the trajectories connecting rods and cylinder block shell or housing does not exceed 10 to 15 mm.Distance between the cylinder bore to the L0 D, it is desirable to be as small as possible and is dependent on many factors:
- Accommodation screws for clamping the head and cylinder block;- The length of rod sleeves and long sleeves of the main beds
- Ways of engine cooling, water or air,
- Type of cylinder liners (dry or wet cylinder liner)The ratio L0 / D for various types of water-cooled engine is in the following bordered:
- L0 / D ≈ 1.2 to 1.28 - for otto engines
- L0 / D ≈ 1.23 to 1.55 - for diesel engines
- L0 / D ≈ 1.68 to - engine performance into V
- L0 / D ≈ 1.30 to 1.44 - for air-cooled diesel engines