Turbocharging is a technology that uses exhaust gas generated by the operation of an internal combustion engine to drive an air compressor.
The role of turbocharging
The main function of turbocharging is to increase the air intake of the engine, thereby increasing the power and torque of the engine, making the car more vigorous. After an engine is equipped with a turbocharger, its maximum power can be increased by 40% or even higher than that without a turbocharger. This also means that the same engine can output more power after being supercharged. Take our most common 1.8T turbocharged engine. After supercharging, the power can reach the level of a 2.4L engine, but the fuel consumption is not much higher than the 1.8L engine. On another level, it is improved. Fuel economy and reduce exhaust emissions.
Negative effects of turbocharging
However, after being supercharged, the pressure and temperature of the engine during operation are greatly increased, so the engine life will be shorter than that of an unsupercharged engine of the same displacement, and the mechanical performance and lubrication performance will be affected. To a certain extent, it limits the application of turbocharging technology in engines.
How turbocharging works
In the working principle diagram of turbocharging, red is high-temperature exhaust gas, blue  is fresh air.
The earliest turbochargers were used in sports cars or formula cars, so in those racing competitions where the engine displacement is limited, the engine can get more power. As we all know, the engine outputs power by burning fuel in the cylinder to do work. Since the amount of fuel input is limited by the amount of air sucked into the cylinder, the power output by the engine is also limited. If the engine’s operating performance is at its best, increasing the output power can only increase the amount of fuel by compressing more air into the cylinder, thereby improving the combustion performance. Therefore, under the existing technical conditions, the turbocharger is the only mechanical device that can increase the output power of the engine without changing the working efficiency.
You may think that the turbocharger is very complicated, but in fact, it is not complicated. The turbocharger is mainly composed of a turbo chamber and a supercharger. First, the intake port of the turbine chamber is connected to the engine exhaust manifold, and the exhaust port is connected to the exhaust pipe. Then the air inlet of the supercharger is connected with the air cleaner pipe, and the air outlet is connected to the air inlet pipe. Finally, the turbine and the impeller are respectively installed in the turbine chamber and the supercharger, and the two are coaxially and rigidly connected. This is a complete turbocharger, your engine is “overclocked” like a computer CPU.
What we usually call a turbocharger is actually an air compressor, which increases the intake of the engine by compressing air. Generally speaking, turbocharging uses the inertial impulse of exhaust gas discharged from the engine to push the turbine into the turbine chamber. , The turbine drives the coaxial impeller, which compresses and transports the air from the air filter pipe, pressurizes it, and enters the cylinder. When the engine speed increases, the exhaust gas discharge speed, and the turbine speed increase simultaneously, and the impeller compresses more air into the cylinder. The increase in air pressure and density can make more fuel fully burned, and the amount of fuel will increase accordingly. Adjust the speed of the engine to increase the output power of the engine.
Classification of turbocharging
According to the way exhaust energy is used in the turbine, it can be divided into the following two systems: According to the way exhaust energy is used in the turbine, it can be divided into the following two systems:
Constant pressure turbocharging system
The constant-pressure turbocharging system collects the exhaust gas of all the cylinders of the internal combustion engine into an exhaust pipe with a large enough volume and then introduces it into the turbine. Although each cylinder is exhausted alternately, the pressure at the inlet of the turbine is basically unchanged due to the stabilizing effect of the exhaust pipe, so it is called a constant pressure booster system.
The main advantages of constant-pressure turbocharging are: the turbine takes in full-circle air under constant pressure, and the efficiency is high; the vibration caused by the airflow is small, and it is not easy to cause blade fracture; the exhaust system is simple, the cost is low, and it is easy to arrange and maintain. The main disadvantage is that the utilization rate of the pulse energy is low. Tests show that when the boost pressure is low, the constant pressure boost system only uses 12% to 15% of the exhaust energy, and can reach more than 30% at high boost pressure. In addition, the constant-pressure supercharged internal combustion engine has poor low-speed torque characteristics and acceleration performance.
Pulse turbocharging system
The impulse turbocharging system is designed to improve the utilization rate of the energy lost in the constant pressure system. The feature of this scheme is that the exhaust pipe is made short and thin, and the volume of the exhaust system should be as small as possible, so that the exhaust can directly and quickly enter the turbine for expansion and work, reducing throttling losses. In addition, in order to reduce the mutual interference of the exhaust pressure waves of each cylinder, two or more exhaust branch pipes are often used to separate the exhaust of adjacent firing cylinders from each other.
The pulse system can better use the exhaust energy of the internal combustion engine than the constant pressure system, and the smaller the exhaust pipe volume, the better so that in recent years, a compact structure that integrates the supercharger and the exhaust pipe has appeared.
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