July 29 2023

Is engine cast iron or all aluminum?

There really is no standard answer to this question. We know that an automobile engine consists of a cylinder head and a cylinder block. An all-aluminum engine refers to an engine whose cylinder block and head are made of aluminum alloy. However, if cylinder head is aluminum alloy and cylinder block is cast iron, it is still a cast iron engine. However, at present, cylinder head materials of many engines are also being replaced by aluminum materials. The reason is not because of its light weight, but more importantly, because aluminum cylinder heads have better heat dissipation characteristics.

Of course, we can also see many higher-end models using all-aluminum engines, purpose of which is to save weight. An all-aluminum engine for same displacement is about 20kg lighter than a cast iron engine. Although this figure is not very high, these models will typically also be lighter in body materials such as suspension materials and other body construction materials. to reduce vehicle weight. For every 10% reduction in vehicle weight, fuel consumption will be reduced by 6-8%, and driving performance will also improve.

However, an all-aluminum engine is not ideal. On one hand, due to lighter specific gravity of aluminum, structural strength per unit volume of aluminum is lower than that of cast iron, so volume of an aluminum cylinder is usually larger than that of cast iron. , it is difficult to achieve compactness and small volume of a cast-iron cylinder. On other hand, aluminum easily reacts chemically with combustion water, so its corrosion resistance is much lower than cast iron cylinders, especially for supercharged engines that require higher temperatures and pressures. At same time, due to volumetric considerations, when a small volume of a car engine is required, it is difficult to use an aluminum cylinder to achieve strength of a cast iron cylinder. In addition, physical characteristics of cast iron and aluminum determine that friction coefficient of a cast iron cylinder block is better than that of an all-aluminum engine, so service life of a cast iron engine is also better than that of an all-aluminum engine. full aluminum engine.

Therefore, although cylinder block and cylinder head of some all-aluminum engines are made entirely of aluminum, cast-iron cylinder liners are integrated into cylinder body, so that piston does not come into direct contact with aluminum cylinder during movement. In this way, service life of all-aluminum engine is guaranteed, and thanks to cast-iron cylinder liner, chemical corrosion in cylinder and a high coefficient of friction between aluminum piston and aluminum cylinder block are prevented. well decided.

(Director: He Shuguang)