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  7. What will -30℃ test?...

[YesAuto Technology] The Dongfeng A9, which will be launched in April this year, is currently rushing to carry out product verification work before launching in the extreme cold areas of China. This is another product that Chinese brands have entered into the medium and large markets. Compared with Bao D80), Zotye (Z700) and even FAW that produces Hongqi H7, Dongfeng A9, which Dongfeng builds with PSA's platform resources, seems to be more interesting at the product level. You must know that this is the most widely used platform for PSA. Before this car was fully revealed, I rushed to the Heihe area where the temperature is close to -30℃. While testing in the cold region, I took this opportunity to have an early experience with this car.

● Where does it go cold?

Dongfeng chose to establish its own cold test base in Wudalianchi, Heihe City, Heilongjiang Province. Days are short and nights are near 50°north latitude. In the coldest January, the long night has a minimum temperature of -30~-40℃. This is undoubtedly a great physical test for us from afar, and Dongfeng testers come here to conduct vehicle tests in cold areas during this time of year.

● What kind of car is “frozen”?

The protagonist of our test today-Dongfeng A9 (the production model of Dongfeng No. 1) is the first medium and large sedan launched by Dongfeng. It is also derived from the Peugeot Citroen Group (PSA) EMP2 along with the Peugeot 308S, 408 and the future generation of Citroen C6. The platform, located at the top of the brand's “pyramid”, represents the highest level of Dongfeng's car manufacturing from styling design, interior configuration to technical application.

After a brief introduction to the Dongfeng A9 (if you want to learn more about the appearance and interior of the Dongfeng A9, you might as well click on the article “To be comparable to the Hongqi H7/Crown real shot Dongfeng No. 1 mass production version”), then we go straight to the topic See what challenges it will accept in severe cold regions?

● Why do we need to conduct a cold zone test?

To put it simply, the cold zone test is a process of “improving if there is any, and reluctant if there is no”. No problem is found is the best result. Because according to the product research and development of a car, the cold area test project has been regarded as the final verification stage of the product. The product at this node has basically been finalized, and generally there will be no major changes. What we need to do now is to carry out real verification tests in addition to the environmental chamber test that simulates low temperature in the R&D center in the early stage of the market, including cold start test, air conditioning system test, defrosting and defogging test, ice and snow field and durability Test etc.

● Cold start test in cold area

Automobile cold start test puts forward high requirements for the normal response of the vehicle's battery, starter, engine electronic system, lubrication system, etc. in a low temperature environment. Two aspects are tested in the cold start test project. One is the start-up time. Dongfeng's test requirement is to start successfully in 10 seconds, and the other is to see whether it can be successfully started at one time. It can be said that the requirement for a successful start within 10 seconds is not high, because most of the current models can complete a cold start in about 2 seconds.

In order to carry out this experiment, we must get up at 6:30 in the morning to prepare for the test with the testers, because the vehicle must complete the test before the temperature rises. Before the test, we saw that the temperature at that time was only -27°C.

In the cold start test project of Dongfeng A9, all electrical equipment with high power consumption, such as headlights, front and rear fog lights, air conditioning system, seat heating, rear windshield heating, etc., needs to be turned on in advance. This is to take into account the different usage habits of users in severe cold areas. Only when all the devices with high power consumption are turned on can the cold-start environment be fully simulated, and the vehicle can have a short start-up time under extreme conditions.

You may wonder whether testers will test the automatic start-stop function (STT) of Dongfeng A9? Dongfeng A9 does come standard with automatic engine start-stop function, but this function is “dumb” in severe cold areas like Heihe.

In addition, after a cold start, the tester will also check the exhaust gas from the exhaust port. If the exhaust gas is white, it means that the engine is working normally; if the exhaust gas is black, it means that the fuel mixture is not burning properly, and it may be possible. There is a problem with the engine ignition system or the three-way catalytic converter.

Since the main products of normal combustion of gasoline engines are water, carbon dioxide, nitrogen oxides, hydrocarbons, and particulate matter, etc., water presents a state of water vapor at high temperatures. After being discharged into the air through a three-way catalytic converter, the water vapor is rapid due to the cold weather. Condensed into tiny water droplets and suspended in the air, then it becomes what we call white “smoke”.

The ice cone at the outlet of the exhaust pipe is produced because the water vapor passing through the three-way catalytic converter condenses in the exhaust pipe and continuously converges into larger water droplets. The last thing that exits the exhaust port is transparent water. Due to the cold weather So it gradually formed a cone of ice. It can be said that the better the catalytic effect of the three-way catalytic converter, the easier it is to form such an ice cone.

● Comfortable experience in cold areas: air conditioning system test

After completing the cold start test, the tester tested the air conditioning and heating system in the car. It can be said that in such a severely cold area, a car with an in-car heating function is another warm “safe haven” besides home. The heating principle of the car's air conditioning system is to use the cooling water circulation to transfer the heat generated by the engine to the heat exchanger of the air conditioner, and then the air conditioner blower blows the heat into the car. During the test, the air conditioner was adjusted to blow to the face, legs and soles of the feet at the same time, and adjusted to the maximum heating state.

For the drivers and passengers in the car, we do not want to enter the car in winter as cold as entering the ice cellar. Therefore, we hope that the heating speed of the air-conditioning system is as fast as possible. We even hope that the seat has a heating function (seat heating and Not from the heat of the engine), no longer have to endure the torment of the ice bottom.

However, for the entire vehicle, it is not possible to blindly pursue the heating performance of the air-conditioning system because of the cold weather, and all the heat generated by the engine is supplied to the vehicle. In order to ensure the normal operation of the engine, its oil temperature and cooling water temperature need to be kept within a certain range. Therefore, the engine needs a complex calibration process to achieve a reasonable thermal management state. This is also one of the most difficult items for vehicle performance debugging in cold areas. One. In fact, what this test really tests is also the engine's thermal management system.

Because the control of the Dongfeng A9 front-seat air-conditioning system has cancelled the physical buttons and knobs, it is all operated and controlled by the display of the center console. So we also need to test whether this LCD screen will cause abnormal display conditions and touch response due to low temperature.

While testing the air-conditioning system in the car, we will also have a simple experience of the riding space of this car to see how much the air-conditioning system needs to provide warm air for the Dongfeng A9's interior space.

For such a positioning model, the comfort of the rear passengers may be more important. If you want the rear to reach the right temperature quickly, the rear air conditioning outlet is indispensable. In the high-end models of Dongfeng A9, an independent control area for rear air conditioning has also been added.

● Defrost and fog test

Frost on car windows is a common occurrence in cold winters. The defrosting method of the front windshield glass of Dongfeng A9 is mainly through the warm air from the air-conditioning outlet under the glass of the front windshield inside the car (without electric heating function), while the frost on the outside rearview mirror and rear windshield glass is caused by Its own electric heating function defrosts.

In theory, there are two ways to remove the water mist on the glass, namely, let the air conditioning system blow hot air and cool breeze. In winter, the vehicle defogging is generally solved by blowing hot air (everyone is not willing to blow cold air in the cold winter). Right), that is, the defrosting process is the same in this environment. The standard for measuring the function of defrosting and defogging is the time used and the area to be removed. The final result is a comprehensive evaluation based on the collected data records and the subjective feelings of the drivers and passengers.

● Driving safety experience in cold areas: field test

In winter, we not only have to deal with cold weather, but because the road is very easy to freeze, one side of the wheel often loses adhesion, so the vehicle must not only provide a warm and comfortable environment for the people in the vehicle, but the most important and basic thing is to ensure that the vehicle Safety of personnel inside. This requires ABS, ESC (Electronic Stability Control Program), snow handling stability and durability in cold areas to be tested in a professional test field.

In the Heihe area, where the latitude is close to 50°, snow covered with silver is everywhere, so for safety reasons, winter tires with better grip are essential. The Dongfeng A9 we tested in this cold region were replaced with “shoes” that are more suitable here (according to insiders, when mass production is launched, the Dongfeng A9 will use the set of Michelin PRIMACY 3ST series tires displayed at the auto show).

We know that the longitudinal pattern of the tire mainly acts as the “drain groove” of the tire and can improve the directivity during driving. The transverse pattern exists to provide sufficient grip and braking performance, close to the lateral side of the tire wall. The pattern will also play a role in drainage. Compared with ordinary tires, winter tires have wider transverse pattern grooves. The wider the grooves, the stronger the braking performance and the gripping ability in snow and mud. The wide pattern grooves bring The negative effect of this is that tire noise will be relatively loud.

For a pair of shoes, we can wear them as long as the specifications match the size of the foot. For a car, if you want a suitable set of snow winter tires, you can't just switch to the right size tires. For example, before the Dongfeng A9 is equipped with a winter tire model, it needs to perform a number of performance matching designs such as tire adhesion coefficient, rolling resistance, ABS, ESC, and vehicle handling stability. Therefore, the selection of the best winter tire is also an item before the cold zone test. important content.

In order to truly reflect the use problems of Dongfeng A9 in cold regions before the launch, the performance evaluation was mainly based on the subjective feelings of testers in the field test. We did not disclose the specific objective test standards to us, but it is simple. This test has given us a general understanding of the cold zone test.

● Summary

Before the launch, we just briefly experienced this Dongfeng A9. If we want to know the most authentic driving experience of this Dongfeng A9, we need to wait for it to go on the market before we will give you a more detailed interpretation. The cold start test, air conditioning system test, defrosting and defogging test, site dynamic test and durability test in the cold area let us know that the production and development of each model must take into account the extreme use environment like Heihe in Heilongjiang For a model such as the Dongfeng A9 with high integration of electrical equipment and rich in-car configuration, extreme environments place higher requirements on its quality and reliability. Whether the final product result meets your requirements, you have the final say after the listing. (Auto House Text/Picture Xia Zhimeng)