In this article we are going to talk about the butt. A key element for the proper functioning of the engine, whose characteristics of design and its materials determine the capabilities that the motor will have. So much so, that it can be modified if an increase in power is sought.
Almost all of the water-cooled engines are provided with a separate cylinder head. Joins the block by means of suitably arranged screws. These ensure the union and prevent deformations due to the action of heat and pressure. In addition, the cylinder head is also attached by a reinforced asbestos gasket, which prevents the gas leak of compression, oil and coolant.
cylinder head materials
In passenger cars, cylinder heads they were manufactured usually from alloy cast iron with other materials, which add characteristics of resistance, rigidity and thermal conductivity. That is, iron and carbon to give rise to steel. However, nowadays there is a greater tendency to choose alloys of aluminum inside cylinder head materials available, for combining lightness with a high degree of thermal conductivity.
The materials that make up the light alloy used for the manufacture of cylinder heads are usually silicon, magnesium, or copper added to aluminum. Otherwise, aluminum alone would be too malleable and brittle to make cylinder heads or engine blocks.
aluminum alloy conducts temperature very well and have one very low thermal inertia. That is, it heats up very quickly and cools down very quickly as well. This characteristic is highly desirable since it ensures that the combustion heat is quickly evacuated to the outside, avoiding the formation of hot spots that can cause combustion. detonation.
With cylinder heads of this type, the compression ratio, to improve thermal efficiency the motor. Something essential to reduce consumption and therefore the emissions of current engines.
The aluminum it is widely used in many parts of carsNot just on the engine. For example, the alloy 6111 aluminum (magnesium and silicon) and the alloy of 2008 aluminum (copper) are widely used for bodywork.
Head gasket materials
As for the materials of the head gasket, they must also meet a series of very important requirements to prevent leaks. Its materials depend on whether it is a soft or hard head gasket.
- All the soft head gaskets They are made of non-asbestos cardboard (without asbestos), cellulose cardboard with nitrile rubber, cork agglomerated with nitrile rubber (old engines only) and elastomers such as nitriles, polyacrylic, silicone, etc.
- All the hard head gaskets They have metal sheets of steel with a tin, chrome or copper coating, which are subjected to heat treatments that offer tempering or elasticity according to the needs of the cylinder head. They also have graphite sheets and non-asbestos (non-asbestos) materials.
Cylinder head features
As with the engine block manufacturing, the cylinder head must be created with the utmost precision. Hence the rectification of a damaged cylinder head It is such an expensive and complicated operation. In addition to this, the cylinder head must have the following characteristics:
Heat resistance
The cylinder head of an engine must withstand high temperatures because in it are the combustion chambers. Cylinder heads made of cast iron have more resistance to heat but dissipate it worse.
Those made of aluminum alloy resist less temperature, but allow it to dissipate much faster. They must also have a large thermal shock resistance, that is, very sudden temperature changes.
Thermal conductivity
The cylinder heads must conduct heat well so that the cooling system can extract the heat generated in the combustion chambers.
Hardness
Whether it is because it is cast or because it is made of a resistant aluminum alloy, the cylinder heads have a suitable hardness to resist high pressure.
In addition, when they are made of aluminum alloy, they are subjected to a age hardening process, also called precipitation hardening, which involves heating the alloy for several hours.
Low porosity of cylinder head materials
During the solidification of the metal used for the cylinder head, catch small gas bubbles. which gives rise to porosity. An undesirable effect so that this important part of the engine has the necessary quality for its performance.
The gas trapped inside consists of steam, air, or burned lubricant. Though also porosity can occur due to lack of pressure in the process or by the mere contraction of the metal as it cools and changes from a liquid to a solid. All of these problems are eliminated or minimized in the manufacture of today's cylinder heads or engine blocks. With what they get higher resistances in modern engines.
Specific cylinder head design
the cylinder heads have a specific shape for each engine because they house many components. These include: the transmission of timing belt or chain, its tensioner, the plugs or ignition system nozzles, valves and their guides, bushings, washers, levers, housings, Camshafts, etc.
In addition, They have very important holes for the engine as they are, the oil ducts and the antifreeze, combustion chambers or the valve seats and the holes to bolt it to the engine block.
Precision manufactured
Each shape and surface of the cylinder head of an engine must have some strictly enforced measures during its creation. Otherwise the motor will not work properly.
An example of this is that if a cylinder head has to be rectified, its manufacturers indicate maximum tolerance levels in each measurement, which are measured in very small fractions of a millimeter.
Images – h080, Nathanael Burton, LC Nøttaasen, Mirko Junge, CORE-Materials
Place the materials with which the cylinder head of a diesel engine is built. Apart from the aluminum alloy, what other material is used?
Do you have any advice to prevent the cylinder head from breaking? That happens a lot.
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