Japanese cars save fuel and have a thin face. It's 2020, don't make people laugh.

In recent years, the development of China automobile industry is obvious to all. The number of cars has increased from 67 million in 2008 to 270 million in 20 19, and it is expected to surpass the United States in 2020 and become the country with the largest number of cars in the world.

We are glad to see that cars have entered the homes of ordinary people, but after all, our automobile industry started late and the popularization time of cars is short, so many citizens still have great misunderstandings about cars.

There are many factors that determine automobile fuel consumption. In addition to external factors such as driving habits and road environment, the displacement, vehicle weight, drag coefficient, engine thermal efficiency and power matching of the car itself will have an impact on fuel consumption. It is not a prominent factor, and the fuel consumption must be low. For example, a big cart is equipped with a small displacement engine, and a big cart is a small horse-drawn cart with the same fuel consumption. Because of this, many people have many misunderstandings about fuel consumption.

Some people drive very lightly and try to keep the engine speed to a minimum, thinking that the lower the speed, the more fuel-efficient. In fact, this kind of cognition is not completely correct.

The reason why engine speed affects fuel consumption is mainly related to engine thermal efficiency. Theoretically, the higher the thermal efficiency of the engine, the more fuel-efficient it is. However, the thermal efficiency of the engine is not fixed, but varies with the engine speed, torque and other factors.

Let's take Camry's 2.5L engine as an example. Officially, the maximum thermal efficiency has reached 40%, but according to the actual test data, the engine power is only 108 when the engine speed is between 1800-2300rpm and the torque is between1-172n m.

Of course, due to the different design of each engine, the most economical speed range is also different, generally between 1300-2800rpm. Generally speaking, anything below or above this speed range is not conducive to fuel economy (except when taxiing).

Generally speaking, the larger the displacement, the higher the fuel consumption, but this conclusion does not apply to all models. Different manufacturers have different R&D capabilities and technical levels, so the fuel consumption of their engines may vary greatly. For example, some domestic 1.5T engines have higher fuel consumption than some joint-venture 2.0T engines.

Even if the same brand uses the same engine technology, the performance of fuel consumption is different due to different models. Generally speaking, the weight and drag coefficient of an SUV are larger than those of the same class, so even if it is equipped with the same powertrain, the fuel consumption of the SUV will be higher, so there will be cases where the SUV equipped with a small displacement engine consumes more fuel than the car equipped with a large displacement.

For example, we learned from the reputation of car home car owners that Tiguan L? The average fuel consumption of 1.4T vehicle is 9.0L/ 100km, and that of Passat 2.0T low-power version is 8.2L/ 100km. The small-displacement Tiguan L is more expensive than the large-displacement Passat.

In addition, for some heavy vehicles, some small horse-drawn carts equipped with small displacement engines are often overloaded, but in order to save fuel, they are not equipped with large displacement engines.

As said at the beginning of the article, there are many factors that affect fuel consumption, and it is not a single one that can decide. The same brand, the same powertrain, in theory, the smaller the car, the more fuel-efficient. After all, the smaller the car, the lighter it is.

But for different brands, it is very different. In real life, you will find that the fuel consumption of many small cars is higher than that of cars several times larger.

For example, the length of the car is less than 4 meters, the wheelbase is less than 2.5 meters, and the weight of the car is less than 1.3 tons. The MINI, which can hardly fit in the back row, is definitely small enough, but the average fuel consumption of the 1.5T model is 8.3L/ 100km, which is not low for such a small car.

In sharp contrast, the length of the car is 4.6 meters, the wheelbase is close to 2.7 meters, and the weight of the car exceeds 1.7 tons. The fuel consumption of RAV4 room equipped with 2.5L hybrid system is only 6.1L.

The above example clearly shows that the smaller the car, the more fuel efficient it is.

In many people's cognition, Japanese cars are more fuel efficient than German cars. Indeed, in the early years, Japanese cars laid a world with high fuel economy, but with the increasingly strict emission regulations, almost all car companies began to pay attention to fuel economy. Nowadays, the fuel consumption performance of Japanese cars in the same class has lost its previous advantages, and even some cars are higher than German cars.

From the statistics of fuel consumption of several mainstream Japanese cars and German cars, we find that many Japanese cars are not necessarily more fuel-efficient than German cars on traditional fuel engines.

Many people judge whether a car is safe or not by simply pressing the hood and closing the door with their hands. If the car is thin and the door is not heavy, then the car is defined as unsafe.

In fact, the thin station wagon mainly affects the NVH and grade sense of the whole vehicle, and at the same time, it will cause greater maintenance costs in small collisions. As for the safety protection of the occupants in the car, it is really not that important.

Compared with the station wagon, the structure and materials of the four beams and six columns and the frame play a vital role in the safety of the occupants in the car.

Many people have a cognitive misunderstanding that the heavier the car, the safer it is, mainly based on the theory that "car weight = good materials, solid steel plates, thick wagons and light cars = cutting corners".

But cars are not all made of steel plates, such as engines, gearboxes and interiors. It also accounts for a large proportion of the weight of the car. Usually, the body-in-white only accounts for 40-50% of the weight of the whole vehicle. Therefore, only looking at the total mass of a car, it is impossible to judge the material of the car frame, because some materials with high rigidity can also be very light, while some seemingly heavy materials are not necessarily good in rigidity.

For example, Lamborghini LP700 uses a lot of carbon fiber materials, so the weight of the whole frame+station wagon is only over 200 kilograms, which is more than twice as light as the average car. Can you say that it is not kind and safe?

Of course, for ordinary models, in the case of similar materials, vehicle weight and lightweight also have their own advantages and disadvantages in terms of safety.

According to Newton's second law, the acceleration of an object is directly proportional to the external force and inversely proportional to the mass (weight) of the object. That is, under the same force, the greater the mass, the smaller the acceleration.

For example, equipped with the same powertrain (1.5L+? CVT) Fit and Binzhi, the former will have better acceleration and braking performance than the latter, and the control is more sensitive.

Therefore, light vehicles can improve active safety and reduce the occurrence of danger through shorter braking distance and more flexible control in an emergency.

However, in terms of passive safety, the weight of the car will be relatively safe. For example, when a big truck collides with a car, the loss of the car is definitely greater than that of the big truck.

According to Newton's third law, when two cars collide, the instantaneous force is equal and the direction is opposite. For example, when a car collides with a big truck, the car may bounce off, but the big truck may hardly move. Under such circumstances, the loss suffered by a light vehicle is definitely greater than its weight.

Many people subjectively think that SUVs are safer than cars because they look tall and rough.

In fact, SUVs have their own advantages and disadvantages in terms of safety. In the same class, SUV will have certain advantages in collision and rear-end collision because of its high body and heavy weight. And because of the high sitting position, good vision and farther vision, you can better observe the surrounding driving environment.

However, the center of gravity of SUV is high, and there is a risk of rollover when changing lanes and cornering at high speed, and rollover is the traffic accident with the highest fatality rate. In addition, due to the high premium of SUVs, SUVs with the same price are often one level lower than cars, so they are not as good as cars in terms of materials and safety design.

It can be seen that many seemingly impeccable perceptions about fuel consumption and safety can't stand scrutiny. Of course, there is no absolute right or wrong. There may be different answers under different conditions. Therefore, for some common car cognition, you should have your own judgment, and don't follow suit. Of course, what other common misunderstandings about cars are welcome to discuss in the comments section.

This article comes from car home, the author of the car manufacturer, and does not represent car home's position.