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What is the steering knuckle

The steering knuckle is the lower half of the crankcase, also known as the lower crankcase. The function is to close the crankcase as the outer shell of the oil storage tank, to prevent impurities from entering, and to collect and store the lubricating oil flowing back from the friction surfaces of the diesel engine, to dissipate part of the heat, and to prevent the lubricating oil from oxidizing.

The steering knuckle (steering knuckle) is located in the lower part of the engine: it can be removed and assembled, and the crankcase is sealed as the outer shell of the oil storage tank. The steering knuckle  is mostly stamped from a thin steel plate, and the more complex shape is generally cast by cast iron or aluminum alloy. The oil stabilizing baffle is installed inside to avoid the oil surface shock and splash caused by the bumping of the diesel engine, which is conducive to the precipitation of lubricating oil impurities. A dipstick is installed on the side to check the amount of oil. In addition, the lowest part of the bottom of the steering knuckle  is also equipped with an oil drain plug.

Classification of steering knuckle 

1. Wet

Most of the cars seen on the market are wet steering knuckles. The reason for the name of the wet steering knuckle is that the crankshaft of the engine and the big head of the connecting rod will be immersed in the oil of the steering knuckle once every revolution of the crankshaft. It plays a lubricating role. At the same time, due to the high-speed operation of the crankshaft, every time the crank is immersed in the steering knuckle at high speed, it will arouse a certain amount of oil and oil mist. In this way, there is a certain requirement for the height of the liquid level of the lubricating oil in the steering knuckle . If it is too low, the crankshaft crank and the large end of the connecting rod cannot be immersed in the lubricating oil, resulting in a lack of lubrication and smooth crankshaft, connecting rod and bearing pad If the lubricating oil level is too high, it will cause the entire bearing to immerse, which will increase the rotational resistance of the crankshaft and eventually cause the engine performance to decrease. At the same time, the lubricating oil will easily enter the cylinder combustion chamber, causing the engine to burn engine oil and spark plug carbon deposits.

This lubrication method has a simple structure and does not require an additional oil tank, but the inclination of the vehicle's work must not be too large, otherwise it will cause a fire and a burning cylinder accident due to oil interruption and oil leakage.

2. Dry

Dry sump is used in many racing engines. It does not store oil in the steering knuckle, more precisely it does not. The friction surfaces of these movements in the crankcase are lubricated by pressing out the oil through the measuring holes. Since the dry steering knuckle engine cancels the function of storing oil in the steering knuckle, the height of the crude steering knuckle is greatly reduced, and the height of the engine is also reduced. The benefit of lowering the center of gravity is that it is beneficial for control. The main advantage is to avoid all the adverse phenomena caused by the intense driving of the wet steering knuckle .

However, because the pressure of the lubricating oil all comes from the oil pump. The power of the oil pump is connected through the gears through the rotation of the crankshaft. Although in the wet steering knuckle  engine, an oil pump is also needed to provide pressure lubrication to the camshaft. But this pressure is very small, and the oil pump requires little power. However, in dry sump engines, the pressure lubrication needs to be much stronger. And the size of the oil pump is much larger than that of the wet steering knuckle  engine. Therefore, the oil pump needs more power at this time. This is like a supercharged engine, the oil pump needs to consume part of the engine's power. Especially at high speeds, when the engine speed increases, the motion intensity of the friction parts increases, and more lubricating oil is required. Therefore, the oil pump needs to provide more pressure, and the consumption of crankshaft power is intensified.

Obviously, such a design is not suitable for ordinary civilian car engines, because it needs to lose part of the engine power, which will not only affect the power output, but also not conducive to improving economy. Therefore, the dry sump will only be equipped on large displacement or high power engines, such as those sports cars that are born for intense driving. For example, Lamborghini uses a dry sump design. For it, it is more important to improve the lubrication effect at the limit and obtain a lower center of gravity. The loss of power can be compensated by other aspects such as increased displacement. As for the economy Sex, this type of car does not need to be considered at all.