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2025
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Truck Encyclopedia (14): Turbocharger Legends
Kajia Encyclopedia gives a brief introduction to the principle of turbocharging. After the article was published, it aroused heated discussions among card friends, and many card friends raised questions about turbochargers. In this issue, Kajia Encyclopedia specially tells you about some rumors of turbocharging, in a question-and-answer manner.
In "With this thing, the motivation is 50% higher!" In the comments of the article, card friends asked: Why turbocharging can increase torque; Why turbocharging is not fuel-efficient; Turbocharging requires a hot car; What is the small rod on the turbocharger used for, and so on. Let's talk about them one by one.
● What is the use of the small rod above the turbocharger?
The rod on the turbocharger is connected to the bypass valve (exhaust valve), and the function of the bypass valve is to control the pressure of the pressurization, which is similar to the pressure cap on the pressure cooker. When the engine speed and exhaust volume are greater than a certain operating point, in order to avoid further increase in the boost pressure, a part of the exhaust gas is discharged through a bypass valve at the turbine.
For example, when the engine is under high speed and heavy load, and the turbocharger boost pressure is too large, the bypass valve is opened, and part of the exhaust gas directly enters the exhaust pipe through the bypass valve, and a part of the exhaust gas is released, and the turbo speed decreases, so as to control the pressure of the boost.
When the wastegate is closed, all the exhaust gases pass through the turbine, and the turbine speed increases, and the boost pressure increases. Therefore, the boost pressure of the turbine can be controlled by controlling the opening and closing of the wastegate.
Therefore, the small pole on the turbocharger is used to control the boost pressure.
● Why does a turbocharger increase torque at low rpm?
Naturally aspirated engines, the air-fuel ratio is a fixed value. Therefore, the maximum torque can only be achieved at a certain speed. With the addition of a turbocharger, the air intake is also increased at low revs, so the maximum torque is much earlier and the range is wider.
The turbocharged engine compresses the gas before entering the cylinder, increases the density of the gas entering the cylinder, reduces the volume of the gas, under the same cylinder working volume condition, the mass of the gas is greatly increased, at this time, the engine increases the amount of fuel injected according to the air intake, to achieve the purpose of improving engine power and torque.
In the vernacular: there is more air participating in the combustion, more oil is sprayed, and the energy of the explosion in the cylinder is greater, and the torque naturally rises.
As a result, the turbocharger can increase the maximum torque of the engine, especially at low rpm.
● The turbocharger power comes from exhaust gases, so will it affect the engine power?
The way the turbocharger is supercharged determines that it will increase the exhaust resistance of the engine, so theoretically, it will affect. But compared to the power increase brought by supercharging, it is not worth mentioning.
The exhaust temperature of a normal engine is about 800-900 degrees, and the exhaust pressure is several times that of the atmospheric pressure. If you don't use exhaust gas energy, it's really a waste.
Therefore, the impact of the turbocharger on engine power is a positive improvement.
In addition, there are some rumors about supercharged engine card friends in the circle, and we will also popularize science together.
● Turbocharged engines are more fuel-efficient?
According to the law of conservation of energy, the more air involved in combustion, the more fuel injection volume also increases, and naturally there is no such thing as fuel saving. Again, if you want your horse to run fast, you have to give your horse more grass.
However, from a technical point of view, after the diesel engine is equipped with a supercharger, the density of the air entering the cylinder increases, the inlet pressure and intake temperature increase, and the temperature and pressure of the compression end working fluid (fuel, air) are increased, so that the lag period is shortened, which is conducive to improving the combustion quality and saving fuel to a certain extent.
In addition, the engine can be more fuel-efficient by optimizing the combustion method, such as higher fuel injection pressure, optimized piston structure, lower frictional resistance, etc. Therefore, the fuel economy is not because the turbocharger is fuel-efficient, but because fuller and more efficient combustion makes the engine fuel-efficient.
Therefore, the turbocharger can make the engine more fuel-efficient to a certain extent.
● Need to warm up the car enough when the turbine engine starts?
As a cliché, let's talk about it here. Regardless of whether the engine is turbocharged or not, after starting the vehicle, wait for the air pressure to come up and then you can drive normally.
Because the original turbocharger has already started to rotate at the beginning of the engine's operation, but because the engine has a low displacement at low speeds, the turbo speed is very low and there is no boost value. Therefore, when the water temperature is low, keep driving gently and try not to increase the engine speed. For articles about hot cars, you can also click on the article "Why is the water temperature low for 10 minutes like a snail crawling".
Therefore, a vehicle with a turbocharger does not need to deliberately heat up the car, and can drive normally after starting.
● Do you need to use fully synthetic engine oil for turbine engines?
No, no, no. In fact, the choice of engine oil during maintenance only needs to be replaced in strict accordance with the requirements of the manufacturer's instructions. As a manufacturer of vehicles, the manufacturer has made sufficient safety redundancy for the maintenance interval and requirements of the engine. As long as you don't die with the Hoho car, or don't use the vehicle according to the instructions, there is no problem.
Therefore, it is not necessary to use fully synthetic motor oil to maintain and use the vehicle in strict accordance with the vehicle instructions.
Well, today's popular science about turbocharging, the card's encyclopedia is here. If you have any questions, you can tell us by leaving a message in the comment area.
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