Which is better, preheating the car in situ or slowly while driving?

The autumn wind is cool, the maple leaves fall, and the shaded trees turn yellow again. How hot is the cold crown block? Ask the old man for help. ? A limerick unveiled today's theme. The weather is getting colder every day, and many friends in the north will struggle with a question, that is, whether the car needs to be heated in place. Most old drivers will tell you that the car must be preheated in place after starting, and then start after the engine temperature rises; However, the operating instructions of many models all say that it is not necessary to preheat the engine in situ after starting, and you can start driving immediately and start preheating slowly while driving. Which of these two diametrically opposed views is correct? How on earth should we warm up the car? This problem will be analyzed for you later.

First of all, what is a hot car? The so-called hot car refers to the process of preheating and warming up the automobile engine, which is also called cold start of the engine. As we all know, the normal working temperature of the engine is generally 80 ~ 90℃, while the ambient temperature is generally between -40 ~ 35℃ ... After the engine is started, the process of rising from the ambient temperature to the normal working temperature is the so-called engine hot car. It can be seen that no matter what engine, no matter where it is, no matter whether it is stationary or starting, the engine has this warming process. Some people say that hot cars are needed in winter and not in summer, which is actually wrong. The engine needs to be warmed up in winter and summer. Even in the hot Middle East, when the ambient temperature is as high as 45°C, there will still be a warm-up process after the engine is started. Therefore, the hot car is actually an essential stage in the engine working process, and no engine can skip this process.

So what is the working state of the engine during the hot car? At this time, the engine is in poor working condition because of low temperature, large gap between parts and high viscosity of engine oil: poor fuel atomization, incomplete combustion and low engine output power; Because of the high running resistance, more fuel will be injected and the concentration of combustible mixture will be high. At this time, the three-way catalyst will not participate in the work, and the exhaust emission will exceed the standard. The engine has poor lubrication performance and serious wear. It is estimated that about 80% of the wear of engine cylinder liner-piston ring friction pair occurs in the cold start stage, and the lower the ambient temperature, the more serious the wear is. In addition, in the cold start stage, the gap between various parts of the engine is large, resulting in a large operating noise.

Therefore, in the cold start stage, the engine performance is poor, and if a large load is applied to the engine at this time, the engine wear will increase greatly. Therefore, the engine must be warmed up after starting. So which is better, heating the car in the original place or starting it slowly while driving? ? First, let's take a look at the hot car. In-situ hot car means that the engine stays still after cold start, and the engine is warmed up at idle speed. At this time, although the driver does not step on the accelerator, in order to overcome the large driving resistance and make the engine warm up quickly, the engine will generally inject more fuel and the idle speed of the engine will be relatively high, and the speed is generally around 1500~2000 rpm. After the engine water temperature rises, the idle speed will gradually decrease until it is reduced to normal idle speed. ? The advantages of in-situ hot car are that the engine is idling and running, the engine is fully lubricated, the lateral pressure between the cylinder wall and the piston and piston ring is small, and the running speed is low, so the engine wear is relatively small at this time; Disadvantages are higher fuel consumption, excessive exhaust emissions and slow temperature rise. If the car warms up at idle for a long time, it will also lead to an increase in engine carbon deposition.

Let's see the hot car moving slowly while driving. There are many car instructions that suggest: don't preheat the engine in place after starting, but start the car at an appropriate speed to let the car warm up while driving. At this time, the engine is working with load. In this state, although the engine speed will be lower than the high idle speed of the cold car, the lateral pressure between the cylinder wall and the piston and piston ring is relatively large, and the engine wear will be relatively large under the condition of poor lubrication. As mentioned above, 80% of the engine wear occurs in the cold start stage, which will actually increase the engine wear. However, when the hot car is driving, the engine temperature will rise faster, and it can cross the cold start stage faster. ? But why do so many car companies require hot cars when driving? This is mainly because, in the cold start stage of the engine, due to the large amount of fuel injection, there is no three-way catalyst, and the exhaust pollution is relatively large; In addition, the waste of fuel in the idle hot car will increase the fuel consumption of the engine. This is against the national policy of energy conservation and emission reduction. Therefore, in order to reduce fuel consumption and exhaust pollution, car companies suggest preheating the car during driving. In fact, this is a method forced by environmental protection policy, which is inappropriate from the perspective of protecting engines.

In fact, the current engine has adopted many methods to make the engine warm up quickly. For example, electronic thermostats, electronic fans, etc. are used. The Volkswagen EA888 engine also adopts an integral cylinder head, and the exhaust manifold is directly integrated inside the cylinder head to quickly raise the engine temperature when the exhaust temperature is high; Honda's 1.5T engine has experienced the failure of increasing oil before, which was largely caused by the long cold start time. After the improvement, more heat is concentrated on the engine, which shortens the cold start time and relieves the fault of increasing oil. Generally speaking, it is a trend to shorten the cold start time of the engine and let the engine warm up quickly.

So how do we warm up the car in daily use? As mentioned above, it is more beneficial to protect the engine to warm the car in situ, so it is essential to warm the car in situ for a period of time after cold start, especially in the cold winter in the north. However, this time should not be too long. It usually takes about a minute. After the engine is started, the oil can reach all lubricating parts in about five seconds, and the core components can reach a higher temperature in about one minute. If the time is too long, it will only waste fuel, increase exhaust pollution and increase the chance of carbon deposition in the engine.

We can start the car after the engine warms up for about a minute. But at this time, the engine has not reached the normal working temperature, and the overall performance is still poor, so it should be used with caution. Do not use the engine under heavy load until the engine temperature reaches the normal working temperature. Control the throttle below 50% and the engine speed below 2500 rpm. Don't accelerate too fast, don't drive too hard, don't shift into high gear too early, and avoid dragging. If you need to climb a steep slope after starting, or start with a full load, it is recommended to extend the time of the original floor heater appropriately and wait until the engine idle speed is reduced before starting driving.