A complete transformation: the new Mercedes-Benz A-Class's technical analysis

Compared with the previous generation of Mercedes-Benz A-Class, the new A-Class can be described as stunning. Whether it is a person or a car, the first thing that attracts people is often the external beauty, but the new A-Class is not just a vase. From the outside to the inside, it has undergone a complete transformation. If you can be patient and take a deeper look, you will find that its inner beauty will be even more irresistible.

The new A-Class has revealed the design direction of Mercedes-Benz's future models from the appearance - youthful and sporty. From the inside out, the new A-Class has a brand-new powertrain, suspension form, body structure and rich active/passive safety configurations. Mercedes-Benz has fully armed the new A-Class with many advanced equipment and a series of high-efficiency energy-saving technologies.

● Hatchback with a drag coefficient as low as 0.27

The exterior design can fully express a designer's inner desire, but if the aerodynamics can be cleverly integrated into the exterior design, it can be said to be a perfect match. Based on the structural characteristics of a hatchback and a short rear overhang, it is very difficult for the new A-Class to achieve a low drag coefficient. Generally speaking, for every 1% reduction in the drag coefficient, the vehicle's fuel consumption per 100 kilometers at a speed of 120km/h will be reduced by 10%.

Through a large number of computer simulations and wind tunnel tests, the new A-Class has achieved a drag coefficient of 0.27, which is a benchmark in the same class. First of all, this is due to the new body structure, which will be mentioned later. In addition, the roof is slightly arched and smooth. In order to make the airflow through the roof cleaner, there is no antenna designed on the roof, and the antenna is cleverly installed in the rear spoiler. A large area of ​​guard plate is used at the bottom of the vehicle to speed up the airflow, and the muffler that cannot be wrapped in it has also been optimized in terms of aerodynamics.

Rotating wheels are often an important factor in causing air turbulence on the vehicle body. The new A-Class has greatly improved the aerodynamic efficiency of this part through the design of the sawtooth front and rear spoiler wheel arches. The shape of the exterior rearview mirrors that stick out on both sides of the body has also been optimized to better guide the airflow to the side of the body. The spoilers on both sides of the rear window are matched with it, which can reduce the generation of vortices at the rear of the hatchback. The front part of the new A-Class is also designed with an intelligent variable air intake grille, which can be opened and closed according to the engine load and temperature conditions, and can effectively reduce the vehicle's air resistance when closed.

In addition to the regular models, the A180 BlueEFFICIENCY (blue efficiency version) can further reduce the drag coefficient to 0.26 through some aerodynamic kits and a lower body (15mm lower than the standard version).

More efficient power system

The previous generation A-Class used a relatively traditional naturally aspirated multi-point electronic fuel injection engine, which was technically a single overhead camshaft + two valves per cylinder design. Although I do not doubt Mercedes-Benz's ability in later tuning, such technical equipment is obviously out of step with the times, and it is even more incompatible with the design concept of the new A-Class. The new A-Class is equipped with a brand-new power system, which also demonstrates Mercedes-Benz's technical strength in small-displacement engines.

■ Gasoline engine

Three of the gasoline engines use dual overhead camshafts and a four-valve per cylinder design. Based on the strategy of a modular platform, the gasoline engine can be arranged horizontally on front-wheel drive vehicles or longitudinally on rear-wheel drive or 4MATIC four-wheel drive vehicles. The A180 is equipped with a 1.6T low-power version engine (122 horsepower/5000rpm, 200 Nm/1250-4000rpm). The A200 is equipped with a 1.6T high-power version engine (156 horsepower/5000rpm, 250 Nm/1250-4000rpm). The A250 is equipped with a 2.0T engine (211 horsepower/5500rpm, 350 Nm/1200-4000rpm).

This 1.6T small-displacement turbocharged engine has good response characteristics through its small inertia turbine and the short-stroke design of the engine itself (cylinder diameter 83 mm/stroke: 73.7 mm), and can output peak torque from 1250 rpm.

——High-precision direct injection + multiple spark ignition system

This small-displacement turbocharged engine, codenamed M270, uses many technologies previously applied to the Mercedes-Benz S-Class V6 and V8 engines. The high-precision direct injection system can achieve 5 injections in one stroke of the engine, fully mixing the fuel and air to achieve better fuel economy. The direct injection system is matched with the MSI multi-spark ignition system, which can make the spark plug ignite 4 times within 1 millisecond to make the mixture burn more fully. It is precisely because of the existence of these two technologies that this turbocharged engine can achieve a compression ratio of 10.3 (usually the compression ratio of turbocharged engines is below 10) without worrying about knocking.

——CAMTRONIC variable valve lift system

Mercedes-Benz introduced variable valve lift technology to small-displacement turbocharged direct injection engines for the first time. Its basic principle is based on Mercedes-Benz's cylinder deactivation technology on large-displacement engines. It is very similar to Audi's AVS technology, both of which achieve changes in valve lift by switching camshafts at different angles. This system can effectively improve the engine's intake efficiency. However, it still cannot achieve stepless adjustment of valve lift like BMW's Valvetronic system. Obviously, the stepless method can control airflow more delicately and accurately.

——Balance shaft technology

Usually, inline 4-cylinder engines will have a certain degree of vibration. In order to eliminate this vibration and obtain better driving comfort, Mercedes-Benz introduced balance shaft technology for this small-displacement engine.

■ Diesel engine

The new generation A-Class also has three more efficient and energy-saving diesel engines, all of which use third-generation common rail direct injection technology. Their official fuel consumption per 100 kilometers is less than 5L, but these models are estimated to be difficult to introduce into the domestic market.

——All models are equipped with engine start-stop system

In order to further reduce emissions and improve fuel economy, the new A-Class series is equipped with an engine start-stop system as standard. After the engine is turned off, the crankshaft position sensor will record the position of the crankshaft at this time. After restarting the engine, the engine computer will determine the stroke to be performed by each cylinder, and then inject fuel and ignite the required cylinders, so that no fuel is wasted during startup.

In addition, with the cooperation of flow-adjustable oil pump, electronic thermostat and more intelligent engine cooling management systems, the fuel economy of this small-displacement turbocharged engine is comprehensively improved.

● 7-speed dual-clutch transmission replaces CVT

The previous generation CVT transmission is obviously no longer suitable for the sporty atmosphere of the new A-Class, so a 7-speed dual-clutch transmission has appeared on the new A-Class in a timely manner. This wet 7G-DCT adopts a 3-axis design, and the speed ratio range reaches 7.99:1. Such a large speed ratio takes into account the engine's low-speed torque and fuel economy during high-speed cruising. The length of 367mm and the weight of 86kg are small and compact. This 7G-DCT also provides three modes: E (economy), S (sports) and M (manual). In addition, the new A-Class also adopts Mercedes-Benz's classic hand-shift design, and the electronic gear lever (relying on electronic buttons to achieve gear shifting) is also more technological.

In order to meet consumers' driving desire for mechanical shifting, the new A-Class is also equipped with a 6-speed manual transmission. The transmission gear part is similar to the 7G-DCT. It also adopts a 3-axis design, with a length of 345mm and a weight of 46kg (excluding transmission oil). Its shell is similar to that of the 7G-DCT, so the layout of the engine compartment does not need to be adjusted significantly due to the choice of transmission.

● Rear suspension changed to multi-link

The new generation A-Class has changed the unique rear suspension structure of the previous generation model with a single-joint arc axle + Watt link, and has adopted a multi-link independent suspension, in which three lateral control arms and one longitudinal arm are all aluminum parts, which can effectively reduce the unsprung mass. The new A-Class can also be equipped with a sports suspension system. In addition, the A250 Sport version is also equipped with a high-performance sports suspension manufactured by AMG, which can effectively reduce the vehicle's roll and pitch during starting and braking.

Electric power steering

The steering system of the new A-Class is still the electric power steering of the previous generation, but the position of the motor has been redesigned and is placed at the gear rack of the steering gear. This electric power steering system can cooperate with ESP to achieve more driving assistance functions. For example, the size of the electric power steering can be adjusted according to the influence of crosswinds, road undulations or different road adhesion, so as to ensure the safety of the vehicle when turning.

In addition, as an option, Mercedes-Benz also offers a direct steering system that is used on models such as the E-Class and S-Class. This system uses racks with different gear ratios to achieve different steering ratios, ultimately giving the vehicle better handling and flexibility.

● The body structure returns to the traditional

The new A-Class is most vividly reflected in its body structure. The sandwich body structure of the old A-Class has been completely abandoned. The engine compartment of the new A-Class has also returned to the layout of a conventional front-wheel drive model, and the oblique horizontal engine that was once specially developed for the sandwich body structure will also be phased out. The new body structure also reduces the height of the new A-Class by 160mm compared to the old A-Class, which is more conducive to the optimization of the body aerodynamics.

● Active/passive safety technology

——Body safety structure + 9 airbags

The proportion of high-strength and ultra-high-strength steel used in the body of the new A-Class is 67%. The front end of the vehicle is designed with a multi-stage dispersed crumple structure, which can maximize the dispersion of collision force to various parts. The front end crumple length is 435 mm, which can maximize the absorption of collision energy in the event of an accident.

The vehicle's B-pillar is made of ultra-high-strength steel. In the event of a side collision, the energy is dispersed to the bottom door sill beam and roof beam through the B-pillar, and then further dispersed through the bottom of the vehicle and the roof crossbar. In the highest-end model, the new A-Class will have 9 airbags, including driver and co-driver airbags (2), front and rear passenger side airbags (4), side airbags (2) and driver knee airbags (1). The driver and co-driver airbags are two-stage, which can be detonated in two stages according to the degree of collision, so as to better protect the occupants.

Mercedes-Benz has equipped the new generation A-Class with many active safety systems. Compared with the previous generation of models which were "naked" in this regard, the new A-Class can be said to be fully armed.

——DISTRONIC PLUS adaptive cruise control system

The system is based on the radar at the front of the vehicle. When the driver turns on this function, the radar waves can keep the vehicle at a fixed distance from the vehicle in front at speeds of 0-200km/h, and automatically respond to the vehicle in front decelerating, accelerating or even stopping. The system can automatically follow the vehicle in front after the vehicle stops completely, especially in stop-and-go congested traffic conditions, which will effectively reduce the driver's operating intensity.

——COLLISION PREVENTION ASSIST Collision Prevention Assist System

When the vehicle speed is within the range of 30-250km/h, the collision prevention assistance system will automatically turn on. It also uses the radar wave at the front of the vehicle to determine the distance to the vehicle in front. When the system detects that the distance to the vehicle in front is too close and a collision may occur, the system will first remind the driver through sound and vision, and at the same time increase the oil pressure of the brake system. If the driver responds and brakes at this time, the system will help the driver to slow down with the maximum braking force. It is worth noting that the system does not brake automatically, but only assists the driver to reduce the possible losses caused by the accident with the maximum deceleration.

——PRE-SAFE system

In particular, the new A-Class is also equipped with the PRE-SAFE system used in higher-level Mercedes-Benz models. This system includes an electrically reversible pre-tensioned seat belt. When the vehicle is in a dangerous situation such as strong oversteer or understeer and side slip, the seat belt will be pre-tightened to restrain the person in the seat, and the system will automatically close the windows and sunroof. Of course, considering the huge pressure generated when the airbag takes effect, the windows and sunroof will retain a gap of about 5 cm to reduce the pressure caused by the airbag popping out. At the same time, the front electric seats with memory function will quickly adjust to the ideal position where the restraint protection system can play the greatest effect. In this way, once the vehicle collides, the occupants will be protected to the greatest extent.

However, it is a bit regrettable that this PRE-SAFE system does not have active braking technology, mainly due to cost considerations. In addition, since the millimeter-wave radar of the active braking technology happens to be in the frequency band controlled by the domestic military, this function cannot be used domestically.

——ATTENTION ASSIST attention warning system

The attention warning system is standard on all Mercedes-Benz A-Class models. The system analyzes and determines whether the driver is in a state of fatigue or low concentration by monitoring the driver's driving actions such as steering and throttle, and then reminds the driver to take necessary rest to improve driving safety.

In addition, the new A-Class's safety assistance systems also include adaptive high beam system, lane keeping assist, blind spot assist system, hill start assist, speed limit assist, etc.

● PARKTRONIC automatic parking function

The automatic parking function is available as an option on the new A-Class. When the vehicle speed is below 35km/h, the radar sensors located at the front and rear bumpers will automatically detect whether there is a suitable parking space on the left or right side of the vehicle. When a suitable parking space appears, a corresponding prompt will appear on the central display screen in the cab. At this time, the driver only needs to follow the instructions to shift gears and control the accelerator and brake (the system speed limit for the entire process is below 10km/h), and the vehicle will automatically turn the steering wheel to complete the parking process.

In addition to automatic parking, the new A-Class also has a new function of automatic exit after parking. The driver only needs to control the accelerator, brake and gear according to the prompts. The vehicle will automatically turn the steering wheel until the vehicle is at a 45° angle to the state just parked. At this time, the driver only needs to drive out of the parking space in a straight line.

● Run-flat tires

The new A-Class is equipped with run-flat tires, which are commonly known as "explosion-proof tires". Therefore, there is no spare tire in the trunk of the new A-Class, only tire repair agent and electric pump, which not only saves space but also reduces the weight of the vehicle. The ABS system will use the wheel speed sensors located on the four wheels to determine whether there is a tire deflation or a tire blowout (the rotation speed of a deflated tire is different from that of a normal tire per unit time), and then remind the driver through the instrument panel. When a tire blows out, the vehicle can still travel at a maximum speed of 80km/h, and can still travel 300km in extreme cases.

● COMAND multimedia system that can be connected to iPhone

Compared with the previous generation, the new A-Class is equipped with Mercedes-Benz's COMAND multimedia system, which can realize functions such as entertainment, comfort system and vehicle settings, and can also be connected with iPhone to realize functions such as Weibo interaction, web browsing and real-time traffic information query. In addition, it also adds voice control function, and the driver can directly control the sound system, make and receive calls, and the navigation system through voice commands.

Summary of the full text:

Mercedes-Benz has transferred the technology originally applied to higher-level models to the new A-Class. The efficient small-displacement turbocharged engine has changed the old appearance of the power system of the previous generation A-Class. The new body structure has achieved an excellent aerodynamic shape while ensuring the interior space and safety. In terms of driving safety assistance systems, the new A-Class is better than the BMW 1 Series and Audi A3 of the same level. In short, the changes in the new A-Class are profound and thorough. Under the premise that the price is still unknown, from a product perspective alone, it is indeed a very competitive product.