This question is so big that I have to answer it in three parts:
Introducing general knowledge about cars
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Contents
1. Main structural parameters and performance parameters of automobiles
2. Detailed explanation of basic engine parameters
3. What are the "Euro I and II" standards
4. Multi-valve engines
5. New car running-in
6. Exploration of car safety ABS ASR ESP
7. Advantages and disadvantages of front and rear wheel drive cars
8. Structure and principle of automatic transmission actuator
9. The role of four-wheel alignment
10. Sports cars
11. Family cars and family sedans
12. Cars Power and economy
13. What kind of car is a luxury sedan according to international convention
14. The difference and division between sedans and hatchbacks
1. The main structural parameters and performance parameters of the car
The main features and technical characteristics of the car vary with the type and characteristics of the engine installed. They usually have the following structural parameters and performance parameters.
1. Vehicle equipment quality (kg): The quality of the vehicle fully equipped, including the quality of all devices such as lubricants, fuel, on-board tools, spare tires, etc.
2. Maximum total mass (kg): the total mass of the car when it is fully loaded.
3. Maximum loading mass (kg): The maximum loading mass of the car when driving on the road.
4. Maximum axle load mass (kg): the maximum total mass carried by a single axle of the car. Related to road passability.
5. Vehicle length (mm): the distance between the two extreme points in the length direction of the vehicle.
6. Vehicle width (mm): the distance between the two extreme points in the width direction of the vehicle.
7. Car height (mm): the distance from the highest point of the car to the ground.
8. Wheelbase (mm): the distance from the center of the front axle of the car to the center of the rear axle.
9. Wheel base (mm): the distance between the center lines of the left and right tire treads of the same car.
10. Front overhang (mm): the distance from the front end of the car to the center of the front axle.
11. Rear overhang (mm): the distance from the rear end of the car to the center of the rear axle.
12. Minimum ground clearance (mm): The distance from the lowest point to the ground when the car is fully loaded.
13. Approach angle (°): The angle between the tangent line from the protruding point of the front end of the car to the front wheels and the ground.
14. Departure angle (°): The angle between the tangent line from the protruding point of the rear end of the car to the rear wheels and the ground.
15. Turning radius (mm): When the car turns, the radius of the trajectory circle of the center plane of the outer steering wheel of the car on the vehicle supporting plane. The turning radius when the steering wheel is turned to the extreme position is the minimum turning radius.
16. Maximum speed (km/h): the maximum speed that a car can reach when driving on a straight road.
17. Maximum gradeability (): the maximum gradeability of the car when it is fully loaded.
18. Average fuel consumption (L/100km): The average fuel consumption per 100 kilometers when the car is driving on the road.
19. Number of wheels and number of driving wheels (n×m): The number of wheels is measured based on the number of wheel hubs, n represents the total number of wheels of the car, and m represents the number of driving wheels. The basic parameters of a car engine include the number of engine cylinders, cylinder arrangement, valves, displacement, maximum output power, and maximum torque.
Number of cylinders: The commonly used numbers of cylinders in automobile engines are 3, 4, 5, 6, and 8 cylinders.
Engines with a displacement of less than 1 liter are usually 3-cylinder engines, 1-2.5 liters are generally 4-cylinder engines, engines with a displacement of about 3 liters are generally 6-cylinder, engines with a displacement of about 4 liters are 8-cylinder, and 12-cylinder engines are used for engines above 5.5 liters. Generally speaking, under the same cylinder diameter, the more cylinders, the larger the displacement, and the higher the power; under the same displacement, the more cylinders, the smaller the cylinder diameter, the speed can be increased, thereby obtaining greater power boost.
Cylinder arrangement: Generally, the cylinders of engines with less than 5 cylinders are arranged in an in-line manner, and a few 6-cylinder engines are also arranged in an in-line manner. The cylinder block of the inline engine is arranged in a line. The cylinder block, cylinder head and crankshaft have a simple structure, low manufacturing cost, good low-speed torque characteristics, low fuel consumption, compact size, and wide application. The disadvantage is low power. The inline 6-cylinder has better dynamic balance and relatively small vibration. Most 6 to 12-cylinder engines are arranged in a V shape. The V shape means that the cylinders are arranged in four rows at staggered angles. The shape is compact. The length and height of the V-shaped engine are small, making it very convenient to arrange. The V8 engine has a very complex structure and high manufacturing costs, so it is rarely used. The V12 engine is too large and heavy, and is only used in a few high-end cars.
Number of valves: Most domestic engines use 2 valves per cylinder, that is, one intake valve and one exhaust valve; foreign car engines generally use a 4-valve structure per cylinder, that is, 2 intake valves, 2 The exhaust valve improves the efficiency of intake and exhaust; some foreign companies have begun to adopt a 5-valve structure per cylinder, that is, 3 intake valves and 2 exhaust valves. The main function is to increase the air intake volume and make combustion more efficient. thorough. The number of valves is not always better. Five valves can indeed improve the air intake efficiency, but the structure is extremely complex and difficult to process, so it is rarely used. The domestically produced new Jetta King uses a five-valve engine.
Displacement volume: The cylinder working volume refers to the gas volume swept by the piston from top dead center to bottom dead center. It is also called single-cylinder displacement. It depends on the cylinder diameter and piston stroke. Engine displacement is the sum of the working volumes of each cylinder, generally expressed in (L). Engine displacement is one of the most important structural parameters. It represents the size of the engine better than the bore and number of cylinders. Many indicators of the engine are closely related to the displacement.
Maximum output power: The maximum output power is generally expressed in horses (PS) or kilowatts (KW). The output power of the engine is closely related to the speed. As the speed increases, the power of the engine also increases accordingly. However, after reaching a certain speed, the power shows a downward trend. Generally, in car instructions, the maximum output power is expressed in terms of rotational speed per minute (r/min), such as 100PS/5000r/min, which means the maximum output power is 100 horsepower at 5000 rpm.
Maximum torque: The torque output by the engine from the crankshaft end. The torque is expressed in N.m/r/min. The maximum torque generally appears in the medium and low speed range of the engine. As the speed increases, the torque On the contrary, it will decrease. Of course, when choosing, you must weigh how to use it rationally and not waste existing functions. For example, it is necessary to turn on the air conditioner in both winter and summer in Beijing. When choosing the engine power, you must consider that it cannot be too small; if you are just using the car for commuting to and from get off work in the city ring, there is no need to choose a high-horsepower engine. Try to be economical and rational in selecting engines.
2. Detailed explanation of the basic parameters of the engine
Number of cylinders: The commonly used numbers of cylinders in automobile engines are 3, 4, 5, 6, 8, 10, and 12 cylinders. Three-cylinder engines are commonly used for engines with a displacement of less than 1 liter, four-cylinder engines with a displacement of 1 to 2.5 liters, 6-cylinder engines with a displacement of about 3 liters, 8-cylinder engines with a displacement of about 4 liters, and 12-cylinder engines above 5.5 liters. Generally speaking, under the same cylinder diameter, the more cylinders, the larger the displacement, and the higher the power; under the same displacement, the more cylinders, the smaller the cylinder diameter, the speed can be increased, thereby obtaining greater power boost.
Cylinder arrangement: Generally, the cylinders of engines with less than 5 cylinders are arranged in an in-line manner. A few 6-cylinder engines are also arranged in an in-line manner. In the past, there were also in-line 8-cylinder engines. The cylinder block of the inline engine is arranged in a line. The cylinder block, cylinder head and crankshaft have a simple structure, low manufacturing cost, good low-speed torque characteristics, low fuel consumption, compact size, and wide application. The disadvantage is low power.
Generally, gasoline engines below 1 liter usually use 3-cylinder in-line gasoline engines. 1 to 2.5-liter gasoline engines mostly use in-line 4-cylinder. Some four-wheel drive vehicles use in-line 6-cylinder. Because of their small width, superchargers and other facilities can be arranged next to them. The in-line 6-cylinder has better dynamic balance and relatively small vibration, so it is also used in some medium and high-end cars, such as the old Shanghai sedan.
6 to 12-cylinder engines are generally arranged in a V shape, among which V10 engines are mainly installed on racing cars. The V-shaped engine has small length and height, making it very convenient to arrange. V-shaped engines are generally considered to be relatively advanced engines and have become one of the symbols of the sedan class. The V8 engine has a very complex structure and high manufacturing costs, so it is rarely used. The V12 engine is too large and heavy, and is only used in a few high-end cars. Volkswagen has recently developed W-type engines, including W8 and W12. That is, the cylinders are arranged in four rows at staggered angles and are compact in shape.
Number of valves: Most domestic engines use 2 valves per cylinder, that is, one intake valve and one exhaust valve; foreign car engines generally use a 4-valve structure per cylinder, that is, 2 intake valves, 2 The exhaust valve improves the efficiency of intake and exhaust; some foreign companies have begun to adopt a 5-valve structure per cylinder, that is, 3 intake valves and 2 exhaust valves. The main function is to increase the air intake volume and make combustion more efficient. thorough. The number of valves is not always better. Five valves can indeed improve the air intake efficiency, but the structure is extremely complex and difficult to process, so it is rarely used. The domestically produced new Jetta King uses a five-valve engine.
Displacement volume: The cylinder working volume refers to the gas volume swept by the piston from top dead center to bottom dead center. It is also called single-cylinder displacement. It depends on the cylinder diameter and piston stroke. Engine displacement is the sum of the working volumes of each cylinder, generally expressed in (L).
Engine displacement is one of the most important structural parameters. It represents the size of the engine better than the bore and number of cylinders. Many indicators of the engine are closely related to the displacement. For cars, displacement is only a relatively important technical parameter. It indicates the approximate power, equipment and price level of the car. However, in China, car engine displacement has other meanings.
Maximum output power: The maximum output power is generally expressed in horses (PS) or kilowatts (KW). The output power of the engine is closely related to the speed. As the speed increases, the power of the engine also increases accordingly. However, after reaching a certain speed, the power shows a downward trend. Generally, in car instructions, the maximum output power is expressed in terms of rotational speed per minute (r/min), such as 100PS/5000r/min, which means the maximum output power is 100 horsepower at 5000 rpm.
Maximum torque: The torque output by the engine from the crankshaft end. The torque is expressed in N.m/r/min. The maximum torque generally appears in the medium and low speed range of the engine. As the speed increases, the torque On the contrary, it will decrease
3. What are the "Euro I and II" standards
In recent years, whether the emissions of automobiles meet the emission standards has become one of the hot topics that people are concerned about. Since September 1, 2001, the country has banned the production and sale of carburetor cars, which has heated up this hot topic. When it comes to emission standards, references to "Euro I" and "Euro II" standards often appear in relevant regulations and articles. So what are "Euro I" and "Euro II" standards?
According to relevant information, "Euro I" and "Euro II" are the abbreviations of European I standards and European II standards. European standards belong to a professional technical category. It is a unified directive formulated by the European Economic Community Committee 91/441/EEC, covering the relevant regulations on emissions of different types of vehicles.
Now take a car with a designed passenger number of no more than 6 people (including the driver) and a total mass of no more than 2.5 tons as an example. During the period from January 1, 1999 to 2003-December 31 , the emission limits that must be reached are: carbon monoxide does not exceed 3.16 g/km, and hydrocarbons do not exceed 1.13 g/km; in addition, the particulate matter emitted by diesel vehicles does not exceed 0.18 g/km, and the durability is 50,000 kilometers. This is the relevant provision in the European Standard I.
After January 1, 2004, this type of gasoline vehicle is required to emit no more than 2.2 g/km of carbon monoxide and no more than 0.5 g/km of hydrocarbons; and no more than 1.0 g/km of carbon monoxide is required from diesel vehicles. km, hydrocarbons shall not exceed 0.7 g/km, and particulate matter shall not exceed 0.08 g/km. This is the relevant provision of the European II standard.
4. Multi-valve engine
On January 29, 1886, German Karl Benz installed his own four-stroke single-cylinder fuel engine on a three-wheeled vehicle. The car was patented and the world really had cars from this day on. It can be said that the engine created the car. The basic structure of the engine (as shown in the picture) is composed of cylinder 1, piston 2, connecting rod 3, crankshaft 4 and other major parts. Each cylinder has at least two valves, an intake valve (blue) and an exhaust valve. (orange color).
The valve gear is an integral part of the engine valve train and plays a very important role in engine operation. The working operation of a fuel engine consists of four working processes: air intake, compression, power generation and exhaust. To make the engine run continuously, these four working processes must be repeated and cycled sequentially and regularly.
Two of the working processes, the intake and exhaust processes, require the K engine's valve mechanism to accurately deliver the combustible mixture (gasoline engine) or fresh air (diesel engine) in accordance with the working sequence of each cylinder. engine), and discharge combustion exhaust gases. For the other two working processes, the compression and power processes, the cylinder combustion chamber must be isolated from the external intake and exhaust channels to prevent gas from leaking to ensure the normal operation of the engine. The component responsible for the above work is the valve in the valve mechanism. It is like the human respiratory organ, inhaling and exhaling, it is indispensable. With the development of technology, the speed of automobile engines has become higher and higher. The speed of modern car engines can generally reach more than 5,500 revolutions per minute. It only takes 0.005 seconds to complete the four working processes. The traditional two-valve system is no longer capable of such tasks. Completing the ventilation work in a short period of time limits the improvement of engine performance. The only way to solve this problem is to expand the space for gas entry and exit. In other words, space is traded for time. Multi-valve technology is the best way to solve the problem. It was not until the promotion of multi-valve technology in the 1980s that the overall quality of the engine made a qualitative leap.
A multi-valve engine refers to a three-valve engine with more than two valves per cylinder, that is, two intake valves and one exhaust valve; two intake valves and two exhaust valves. Four-valve type; five-valve type with three intake valves and two exhaust valves. Currently, most multi-valve engines in cars are four-valve. A four-cylinder engine has 16 valves, a six-cylinder engine has 24 valves, and an eight-cylinder engine has 32 valves. For example, the engine of the Japanese Lexus LS400 sedan has 8 cylinders and 32 valves. When the number of valves is increased, the corresponding valve mechanism device is added, and the structure is relatively complicated. Generally, two overhead camshafts are used to control the valves arranged on both sides of the center line of the cylinder combustion chamber. The valves are arranged at inclined positions on both sides of the center of the cylinder combustion chamber in order to expand the diameter of the valve head as much as possible, increase the airflow passing area, improve ventilation performance, and form a compact combustion chamber with the spark plug in the center, which is beneficial to the mixing of the mixture. Burns quickly.
Some people have asked, since the valves are so good, why can’t we see engines with more than 6 valves per cylinder? There is a concept in thermodynamics called "curtain area", which refers to the circumference of the valve multiplied by the lift of the valve, that is, the space in which the valve opens. The larger the "curtain area" is, the larger the space for the valve to open and the greater the air intake volume. Taking the engine of the Audi 100 sedan as an example, its four-valve "curtain area" value is half greater than the two-valve "curtain area" value in the intake state and 70% greater in the exhaust state. . Of course, everything has its certain scope of application. It does not mean that the more valves, the greater the "curtain area" value. According to expert calculations, when the number of valves in each cylinder is increased to six, the "curtain area" value will actually increase. The more valves there are, the more complex the mechanism, and the greater the cost. Therefore, the number of valves in each cylinder of current multi-valve fuel engines for cars is three to five, with four valves being the most common.
Take gasoline engines as an example. Compared with traditional two-valve engines, multi-valve engines can suck in more air to mix fuel and burn for work, save fuel, discharge exhaust gas faster, and emit pollution. Less, it can improve engine power and reduce noise, which is in line with the development direction of optimizing the environment and saving energy, so multi-valve technology can be quickly promoted.
With the continuous improvement of technology, this technical defect of multi-valve gas engines has been gradually overcome. Now, almost all mid- to high-end cars in the world are equipped with multi-valve fuel engines.
5. New car running-in
There has been too much talk about the topic of new car running-in! Regardless of whether you have a car or not, as long as you pay attention to cars, Know that there is a running-in phase for new cars. Regarding the running-in of a new car, many people don’t understand what exactly is running-in. Many people think that as long as the parts that move relatively have a running-in process, some people have unnecessarily added a lot of precautions to the running-in of a new car. Therefore, many people are either too cautious during this running-in period, or they are paying attention while unconsciously violating the running-in requirements. Here, we will discuss: What is the running-in of a new car? In addition to normal use and maintenance, what other matters need special attention during the running-in stage?
The initial period when a new car is put into use is called the running-in stage of the car. Each manufacturer recommends a running-in mileage to users, generally 1,000-2,000 kilometers, and some models have a running-in mileage of 2,000-3,000 kilometers.
During this running-in stage, people naturally think that moving parts such as shafts and bearings in the engine, gearboxes, clutches, brake components, and drive shafts all need to be run-in. This is obviously not "wrong", but it is also It cannot be considered "right", because the "grinding" between these parts is certain, and "fitting" is really out of the question. According to current mechanical design, processing technology and assembly technology, these parts no longer need to be "grinded" to make them fit and work better. So, what exactly is running in? The running in here refers to the fit between the piston ring and the cylinder wall inside the engine!
In the engine. Since the temperature and pressure in the cylinder are very high, the high-speed moving piston cannot seal directly through direct contact with the cylinder wall. There is a moving gap between the two, and the sealing is ensured by the piston ring. Piston rings are usually composed of gas rings and oil rings. As the name implies, the gas rings are used to seal the gas (prevent the mixture or exhaust gas in the cylinder from entering the crankcase to avoid engine power reduction and prevent contamination of the engine oil), and the oil rings are used to seal the gas. Oil (because the crankshaft will throw the oil in the crankcase onto the cylinder wall, the role of the oil ring is to scrape off the oil. Prevent the oil from entering the combustion chamber and causing oil burning).
From the above introduction, two important points should be noted: 1) The engine needs piston rings to build up cylinder pressure during operation; 2) The piston rings are a key component for running-in. Therefore, for piston rings, whether in the "running-in" period or in the subsequent "wear" period, it must seal the gap between the cylinder wall and the piston. In this way, the outer diameter of the piston ring needs to be slightly larger than the cylinder diameter, and The function of the opening is to facilitate assembly and to automatically fine-tune the diameter as it wears. In new engines, the piston rings and cylinders of different diameters assembled together will have slight differences in roundness, and the processing errors in their respective sizes will cause gaps in the contact surfaces between the two. For high-pressure cylinders, the impact of this gap is really not small!
When a new car leaves the factory, the piston ring and cylinder wall of the engine have not been run-in, and there is a gap in the contact surface, so that the pressure in the cylinder cannot reach The design requirements affect the combustion of fuel, and the engine may lack power and work poorly. After thousands of kilometers of running-in, the piston ring and the cylinder wall gradually have an excellent fit, so that the cylinder pressure reaches the design value, and the engine enters the Best working condition. This is why some people say: After the running-in period, the overall feeling of the engine will be better, and the fuel consumption will also be improved! The engine after overhaul has a running-in period, and it is for the same reason.
How to correctly use and maintain a vehicle, there are many things in it, which most drivers know, such as: generally do not overload; do not tow or tow other vehicles or equipment; choose according to the user manual Fuel of specified label and engine oil of specified type; frequently check gear oil (or automatic transmission fluid), brake fluid, steering assist fluid, clutch assist fluid, antifreeze, etc. and replace (or add) as required; check Tire pressure; always pay attention to the tightening of various parts. The engine oil replacement time will be slightly different during the running-in period, because the cylinder seal is not very good, and unburned mixture and burned exhaust gas may enter the crankcase. This will speed up the deterioration of the engine oil, so it is better to change the engine oil earlier.
According to the above introduction to running-in, there are two precautions that are directly related to running-in:
1. Avoid high-speed
due to flake annular shape There is a gap between the piston ring and the cylinder wall, and only some sections and points are actually in contact. During the running-in process, the excessively high engine speed will naturally increase the possibility of linting, straining the cylinder, and damaging the piston rings. Therefore, general manufacturers will recommend that the speed limit of new cars be 80-90 km/h. In the speed range of 80-90 km/h, whether it is a manual transmission car or an automatic transmission car, the automatic speed switching point is set according to the normal shifting requirements. The engine speed in this speed range is around 2500 rpm, with a maximum speed of about 2500 rpm. It will not exceed 3000 rpm. This is the key and essence of the vehicle speed limit: limiting the vehicle speed actually limits the engine speed! "Do not artificially speed up the engine during the running-in period." I hope some novices will pay attention to this point. Some people think that "as long as the vehicle speed does not exceed the recommended speed limit, the high-speed operation of the engine does not matter." In fact, this is contrary to the speed limit recommendations.
At the same time, it is also very taboo to "shift into high gear at low speeds". Frequent bumps caused by insufficient power may also cause hair pulling, strain on the cylinder wall and damage to the piston rings. Also, don't stay at a certain speed for a long time, whether it's high speed or low speed. By the way, shifting gears, although this is not part of the running-in process. Shifting gears depends on the speed of the car, not the engine speed. "20km/h shifts to second gear, 40km/h shifts to third gear, 60km/h shifts to fourth gear, and 70km/h shifts to fifth gear" is the best, and the corresponding The vehicle speed range is the best design efficiency range for each gear. The statement "low speed and high gear to save fuel" is not correct, because you cannot save fuel when it may damage the engine, otherwise. The money saved on gasoline is not enough to compensate for the shortened service life caused by poor engine conditions.
2. Driving gently
During the running-in phase, the requirement of driving gently is beneficial to all moving parts, especially the cylinders that are running in. Avoid the word "hurry", don't accelerate suddenly, and avoid sudden braking within the first few hundred kilometers.
At this point, I wonder if people understand it? In fact, as long as you drive normally and correctly, you can successfully pass the running-in stage. Moreover, with the improvement of mechanical manufacturing technology, the piston rings and cylinder walls of new car engines have been well matched. The running-in of new cars is no longer "mandatory" but a "suggestion"! Of course, cars are very important to individuals. , considered a great asset, it is best to treat your car well according to the "suggestions".
6. Exploration of car safety ABS ASR ESP
When ABS (anti-lock braking system) first came out, people were amazed by its excellent safety. The installed car not only shows that its safety performance is outstanding, but also the grade is quite high. Today, cars equipped with ABS are quite common, and economy cars are also equipped with ABS. And as the requirements for automobile safety performance become higher and higher, some more advanced safety devices with a wider range of protection have been introduced, including ASR (anti-skid drive system, also known as traction control system) and ESP (electronically controlled driving system). Stability system) is the most representative, and their birth has further improved the safety performance of cars.
ASR: Drive Anti-Slip System (or Traction Control System)
A car's traction control can be achieved by reducing the throttle opening to reduce engine power or by brake control and wheel slip. Purpose, cars equipped with ASR work by combining these two methods, that is, ABS/ASR.
The function of ASR is to control the sliding force within a certain range when the car accelerates, thereby preventing the driving wheels from sliding rapidly. Its function is to improve traction; second, to maintain the driving stability of the car. When driving on a slippery road, the driving wheels of a car without ASR are prone to slipping when accelerating; if it is a rear-drive vehicle, it is easy to drift; if it is a front-drive vehicle, it is easy to lose control of the direction. With ASR, this phenomenon will not occur or can be mitigated when the car accelerates. When turning, if the driving wheel slips, it will cause the entire vehicle to shift to one side. When ASR is present, the vehicle will turn along the correct route.
In vehicles equipped with ASR, the mechanical connection from the accelerator pedal to the gasoline engine throttle (diesel injection pump operating lever) is replaced by an electronically controlled throttle device. When the sensor sends the position of the accelerator pedal and the wheel speed signal to the unit (CPU), the control unit will generate a control voltage signal, and the servo motor will readjust the position of the throttle (or the position of the diesel engine joystick) based on this signal, and then This position signal is fed back to the control unit so that the brakes can be adjusted in time.
ESP: The full English name of the electronically controlled driving stability system is Electronic StabiltyProgram, which is an extension of the functions of ABS and ASR. Therefore, ESP can be regarded as the most advanced form of current automobile anti-skid device.
The ESP system consists of a control unit and a steering sensor (monitoring the steering angle of the steering wheel), a wheel sensor (monitoring the speed of each wheel), a sideslip sensor (monitoring the rotation of the car body around the vertical axis), a lateral Acceleration sensor (monitors the centrifugal force when the car turns) and other components. The control unit uses the signals from these sensors to judge the operating status of the vehicle and then issues control instructions. The difference between cars with ESP and cars with only ABS and ASR is that ABS and ASR can only react passively, while ESP can detect and analyze vehicle conditions and correct driving errors before they happen. ESP is particularly sensitive to oversteer or understeer. For example, when a car turns left and oversteers (turns too sharply) on a slippery road, it will drift to the right. When the sensor senses the slip, it will quickly brake the right front wheel to restore steering. Apply force to produce an opposite torque to keep the car in the original lane.