First of all, the specific gravity of aluminum is lighter than cast iron in terms of quality. Under the premise of meeting the strength requirements, the aluminum cylinder block is much lighter. The lighter engine can exert a positive influence on the weight distribution of the entire vehicle, and the weight of the entire vehicle is also lighter. Therefore, at this point, the aluminum cylinder block is dominant. However, the specific gravity of aluminum is light, and the structural strength of aluminum per unit volume is less than that of cast iron, so aluminum cylinders are usually larger in volume. Except for the cooling water channel, the cylinder wall is actually quite thin. In this way, the entire engine is very compact and small in size. Aluminum cylinders are more difficult to achieve this effect.
Aluminum is easy to chemically react with water produced during combustion, and its corrosion resistance is not as good as that of cast iron cylinder blocks, especially for supercharged engines with higher temperature and pressure. Therefore, when the size of the car’s engine is small, it is difficult to achieve the strength of the cast iron cylinder block by using aluminum cylinder block. Therefore, most high-supercharged engines use cast iron cylinders. Aluminum conducts heat faster, so it has good cooling performance, which can help the engine reduce the probability of abnormal combustion. At the same compression ratio, aluminum cylinder engines can use lower-grade gasoline than cast iron cylinder engines.
In the current engine, in order to reduce the inertia of the reciprocating parts and increase the speed and response speed, most of the pistons use aluminum alloy as the material. If the cylinder wall is also aluminum. The coefficient of friction between aluminum and aluminum is relatively large, so the performance of the engine is greatly affected. Engines with cast iron blocks do not have this problem.
In the engine casting, the cast iron production line occupies a large area, which pollutes the environment and the processing technology is complicated; while the production characteristics of cast aluminum cylinder blocks are just the opposite. From the perspective of market competition, cast aluminum cylinder blocks have certain advantages. Due to the advantages of cast aluminum cylinder blocks, for example, Japan mainly develops engines with cast aluminum cylinder blocks. However, most of the engines produced by Toyota in China are cast iron block engines. One of the reasons is that China’s raw materials are not as scarce as Japan. Judging from the current situation, the price of aluminum on the market is not low, which weakens the advantage of cast aluminum engine in the production and processing. The heat load capacity of the cast iron cylinder block is stronger, and the potential of cast iron is greater in terms of engine power per liter. For example, the output power of a 1.3-liter cast iron engine can exceed 90kW, while the output power of a cast aluminum engine can only reach 60kW. It is understood that the 1.5-liter cast iron engine can be It meets the power requirement of an engine with a displacement of 2.1 liters or more, but it is difficult for a cast aluminum engine to meet this requirement.
Link to this article：Comparative analysis of cast iron engine and all-aluminum engine
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