Wet type
Wet Sump
Most cars seen on the market are equipped with wet oil pans. The reason why they are named wet oil pans is because the crankshaft and connecting rod of the engine are immersed in the lubricating oil of the oil pan every time the crankshaft rotates, providing lubrication. At the same time, due to the high-speed operation of the crankshaft, each time the crankshaft is immersed in the oil pool at high speed, it will cause certain oil splashes and oil mist to lubricate the crankshaft and bearing shells, which is called splash lubrication. In this way, there are certain requirements for the liquid level height of the lubricating oil in the oil pan. If it is too low, the crankshaft and connecting rod big end cannot be immersed in the lubricating oil, resulting in a lack of lubrication and smooth crankshaft, connecting rod, and bearing shells; If the lubricating oil level is too high, it will cause the entire bearing to immerse, increase the rotational resistance of the crankshaft, and ultimately lead to a decrease in engine performance. At the same time, lubricating oil is prone to enter the combustion chamber of the cylinder, causing problems such as engine oil burning and spark plug carbon accumulation.
This lubrication method has a simple structure and does not require an additional oil tank, but the inclination of the vehicle during operation should not be too large, otherwise it may cause tile burning and cylinder pulling accidents due to oil cut-off and leakage.
dry-type
Dry Sump
Dry oil pan is used in many racing car engines. It does not store engine oil in the oil pan, more accurately, there is no oil pan. The friction surfaces of these movements in the crankcase are lubricated by pressing out oil through measuring holes. Due to the cancellation of the oil storage function of the dry oil pan engine, the height of the crude oil pan is greatly reduced, and the engine height is also lowered accordingly. The benefit of a lower center of gravity is beneficial for handling. The main advantage is that it avoids the adverse effects of wet oil pan caused by intense driving.
However, due to the fact that all lubricating oil pressure comes from the oil pump. The power of the oil pump is connected through gears through the rotation of the crankshaft. Although in wet sump engines, an oil pump is also required to provide pressure lubrication for the camshaft. But this pressure is very small, and the power required by the oil pump is also very small. However, in dry oil pan engines, the strength of this pressure lubrication needs to be much greater. Moreover, the size of the oil pump is much larger than that of the oil pump in wet pan engines. So at this point, the oil pump requires more power. This is like a turbocharged engine, where the oil pump needs to consume a portion of the engine's power. Especially at high speeds, as the engine speed increases, the intensity of the friction components also increases, requiring more lubricating oil. Therefore, the oil pump needs to provide greater pressure, which exacerbates the consumption of crankshaft power.
Obviously, this design is not suitable for ordinary civilian vehicle engines, as it requires the loss of some engine power, which not only affects power output but also is not conducive to improving fuel efficiency. Therefore, a dry oil pan will only be equipped on high displacement or high-power engines, such as sports cars designed for aggressive driving. For example, the Lamborghini adopts a dry oil pan design. For it, improving the lubrication effect at the limit and obtaining a lower center of gravity are more important, and the power loss can be compensated for by increasing displacement and other aspects. As for economy, this type of vehicle does not need to be considered completely.