Turbochargers are often used to increase the intake air volume of an internal combustion engine, thereby increasing horsepower output.
What is Turbocharging (Turbo)?
A turbocharger is an air compressor driven by the exhaust gas generated by the operation of an internal combustion engine through a structure composed of a stator and a rotor. Similar in function to a supercharger, both increase the flow of air into an internal combustion engine or boiler, making the machine more efficient. It is commonly used in automobile engines. By using the heat and flow of exhaust gas, turbochargers can increase the horsepower output of internal combustion engines. Some vehicles use turbochargers not to increase engine power, but through turbochargers. With an engine with a smaller cylinder volume, fuel economy and environmental protection can be improved without sacrificing the engine output performance.
Generally, the weight of an internal combustion engine for a vehicle will increase after adding a supercharger, and the energy used to overcome inertia will increase. Because the turbocharger uses the exhaust gas from the engine as its power source most of the time, it has advantages over the supercharger driven by the engine crankshaft. However, when the engine is running at a low speed, the exhaust gas flow rate is low, so when the blade speed of the turbocharger does not meet the minimum requirement, the supercharging performance is not as ideal as that of the supercharger, and turbo lag occurs. However, with the development of technology, turbochargers have been intervened earlier to improve engine efficiency at low speeds.
Generally speaking, if we see Turbo or T at the rear of a car, it means that the engine used in the car is a turbocharged engine. The function of turbocharging is to increase the air intake of the engine, thereby increasing the power and torque of the engine, so that the car has more power to rotate and transmit. After an engine is equipped with a turbocharger, its maximum power can be increased by 40% or even higher than that without a supercharger. This means that the same engine can produce more power after being supercharged.
For example, in the 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 that of a 1.8 engine. On another level, it is to improve fuel economy and reduce exhaust emissions. However, after supercharging, the pressure and temperature of the engine are greatly increased when it is working. Therefore, the life of the engine will be shorter than that of an engine with the same displacement that has not been supercharged, and the mechanical performance and lubrication performance will be affected, which also limits the application of turbocharging technology to the engine to a certain extent.
The Principle of Turbocharging:
The earliest turbochargers were used in sports cars or formula cars so that the engine could obtain more power in racing competitions where the engine displacement was limited.
The engine generates power by burning fuel in the cylinder because the amount of fuel input is limited by the amount of air in the cylinder. Therefore, the power generated by the engine will also be 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 current technical conditions, the turbocharger is the only mechanical device that can increase the output power of the engine while the working efficiency remains unchanged.
A turbocharger is an air compressor that increases the air intake of the engine by compressing air. Turbocharging uses the inertial momentum of the exhaust gas discharged from the engine to drive the turbine in the turbine chamber, and the turbine drives the coaxial impeller, which presses the air sent by the air filter pipe to pressurize it into the cylinder.
When the engine speed increases, the exhaust gas discharge speed and the turbine speed also increase synchronously, and the impeller compresses more air into the cylinder. The pressure and density of the air increase to burn more fuel. Increase the fuel volume and adjust the engine accordingly. speed, the output power of the engine can be increased.
The turbocharging device is not complicated. The turbocharging device is mainly composed of a turbine chamber and a supercharger. First of all, 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 intake port of the supercharger is connected to the air filter pipe, and the exhaust port is connected to the intake manifold. Finally, the turbine and the impeller are installed in the turbine chamber and the supercharger respectively, and the two are coaxially rigidly connected.
Types of Turbo:
- Mechanical supercharging system:
This device is installed on the engine and connected to the crankshaft of the engine by a belt and obtains power from the output shaft of the engine to drive the rotor of the supercharger to rotate, thereby blowing supercharged air into the intake manifold. The advantage is that the turbo spins at the same speed as the engine, so there is no lag and the power delivery is very smooth. However, because it is installed in the rotating shaft of the engine, it still consumes part of the power, and the effect of supercharging is not high.
- Airwave booster system:
Air compression is forced by pulsed airwaves of high-pressure exhaust gas. This system has good supercharging performance and good acceleration, but the whole device is relatively heavy and is not suitable for being installed in a car with a small volume.
- Exhaust gas turbocharging system:
This is the most common turbocharging device. The supercharger has no mechanical connection to the engine. It is an air compressor that increases the intake of air by compressing air. It uses the inertial momentum of the exhaust gas discharged from the engine to drive the turbine in the turbine chamber, and the turbine drives the coaxial impeller, which presses the air sent by the air filter pipe to pressurize it into the cylinder. When the engine speed increases, the exhaust gas discharge speed, and impeller speed also increase synchronously, and the impeller compresses more air into the cylinder, and the pressure and density of the air increase to burn more fuel, and the corresponding increase in fuel volume can increase the engine capacity. output power. The power and torque of the engine after installing the exhaust gas turbocharger will increase by 20%-30%. However, exhaust gas turbocharger technology also has its points that must be noted the pump wheel and the turbine are connected by a shaft. The exhaust gas discharged from the engine drives the pump wheel, and the pump wheel drives the turbine to rotate. pressure. The supercharger is installed on the exhaust side of the engine, so the working temperature of the supercharger is very high, and the speed of the rotor is high when the supercharger is working, which can reach hundreds of thousands of revolutions per minute. Such a high speed and temperature make common mechanical needle or ball bearings unable to work for the rotor, so turbochargers generally use full floating bearings, which are lubricated by oil and cooled by coolant.
- Compound booster system:
That is, exhaust gas turbocharging and mechanical supercharging are used together. This device is often used in high-power diesel engines. The engine output power is large, the fuel consumption rate is low, and the noise is small, but the structure is too complicated, the technical content is high, and the maintenance is not enough.
The Disadvantages of Turbocharged Engines:
Turbocharging can indeed increase the power of the engine, but it also has many shortcomings, the most obvious of which is the lag in power output response. Due to the inertia of the impeller, the response to the sudden change of the accelerator is slow. There is a time difference between stepping on the accelerator to increase the horsepower and turning the impeller to press more air into the engine to obtain greater power, and this time is not short. Generally, the improved turbocharger takes at least 2 seconds to increase or decrease the engine power output. If you accelerate suddenly, you will feel that you can't increase the speed in an instant.
With the advancement of technology, although various turbocharger manufacturers are improving turbocharger technology, due to design principles, the feeling of driving a car equipped with a turbocharger is the same as that of a car with a large displacement. If your car is often driven in the city, it is really necessary to consider whether a turbo is needed, because the turbo is not always activated. In fact, in daily driving, there are very few opportunities for the turbo to be activated, or even not used, which has an impact on the daily performance of the turbocharged engine.
In addition, turbocharging also has maintenance problems. For 1.8T, the turbo will need to be replaced at about 60,000 kilometers. Although the number of times is not too much. After all, it has added a maintenance fee to one's car, which is particularly noteworthy for car owners whose economic environment is not particularly good.
The Use of Turbocharged Engines:
The turbocharger uses the exhaust gas from the engine to drive the turbine. No matter how advanced it is, it is still a set of mechanical devices. Because its working environment is often at high speed and high temperature, the temperature at the turbine end of the supercharger is above 600 degrees. The speed of the supercharger is also very high, so to ensure the normal operation of the supercharger, it is important to use and maintain it correctly.
- After starting the car engine, do not step on the accelerator pedal quickly but run it at idle speed for three minutes. This is to increase the temperature of the engine oil and improve the flow performance so that the turbocharger can be fully lubricated, and then the engine speed can be increased to start driving. Especially important in winter, and it takes at least 5 minutes to warm up the car.
- After the engine has been running at high speed for a long time, it cannot be turned off immediately. The reason is that when the engine is running. A part of the engine oil is supplied to the turbocharger rotor bearing for lubrication and cooling. After the running engine suddenly stops, the oil pressure drops to zero rapidly, the oil lubrication will be interrupted, and the heat inside the turbocharger cannot be taken away by the oil. At this time, the high temperature of the turbine part of the turbocharger will be transmitted to the middle, and the heat in the bearing support shell cannot be taken away quickly, while the supercharger rotor is still rotating at a high speed under the action of inertia. This will cause the turbocharger shaft to be stuck between the shaft sleeve and damage the bearing and shaft. In addition, after the engine is suddenly turned off, the temperature of the exhaust manifold is high at this time. And its heat will be absorbed by the turbocharger housing, and the engine oil staying inside the turbocharger will be boiled into carbon deposits. When this carbon deposit accumulates more and more, it will block the oil inlet, resulting in an oil shortage of the shaft sleeve, and accelerating the wear between the turbine shaft and the shaft sleeve. Therefore, before the engine is turned off, it should be idled for three minutes to reduce the speed of the turbocharger rotor. In addition, it is worth noting that turbocharged engines are also not suitable for long-term idling, and should generally be kept within 10 minutes.
- Be careful when choosing engine oil. Due to the role of the turbocharger, the quality and volume of the air entering the combustion chamber are improved, the engine structure is more compact and reasonable, and the higher compression ratio makes the engine work more intensively. The precision of machining is also higher, and the requirements for assembly technology are stricter. All of these determine the high temperature, high speed, high power, high torque, and low emission working characteristics of the turbocharged engine. At the same time, it also determines the working conditions that the internal parts of the engine must withstand higher temperatures and greater impact, extrusion, and shearing forces. Therefore, when selecting engine oil for turbocharged cars, it is necessary to consider its particularity. The oil used must have good wear resistance, high-temperature resistance, build a lubricating oil film block, high oil film strength, and good stability. Synthetic engine oil or semi-synthetic engine oil can just meet this requirement, so in addition to the best engine oil specified by the original factory, high-quality lubricating oils such as synthetic engine oil and semi-synthetic engine oil can also be used.
- The engine oil and filter must be kept clean to prevent impurities from entering because the fit gap between the turbocharger shaft and the bushing is very small, if the lubricating ability of the engine oil decreases, the turbocharger will be scrapped prematurely.
- It is necessary to clean the air filter on time to prevent dust and other impurities from entering the high-speed rotating compressor impeller, resulting in unstable speed or increased wear of shaft sleeves and seals.
- It is necessary to check frequently whether the sealing ring of the turbocharger is the bee. Because if the sealing ring is not sealed, the exhaust gas will enter the engine lubrication system through the sealing ring, which will make the oil dirty and the pressure of the crankcase will rise rapidly. In addition, the oil will also be discharged from the exhaust pipe through the sealing ring or enter the combustion chamber for combustion, resulting in excessive consumption of engine oil and burning engine oil.
- The turbocharger should be checked frequently for abnormal noise or unusual vibration, and leakage of lubricating oil pipes and joints.
- The precision of the turbocharger rotor bearing is very high, and the working environment requirements for maintenance and installation are strict. Therefore, when the turbocharger fails or is damaged, it should be repaired at a designated repair station instead of an ordinary repair shop.