[YesAuto reveals the new car technology] Not long after the new Audi Q7 was launched, the Audi SQ7 (hereinafter referred to as SQ7) appeared at the Geneva Motor Show. As a performance-oriented medium and large SUV, Audi SQ7 not only uses traditional methods (such as “hard vibration damping”) to transform the vehicle into sports, it also starts with “black technology” to make SQ7 possess Nearly all of Audi’s advanced technology. These technologies may make you “thinking confused” because of the complexity of the logic. Don't be afraid. Below we will use relatively popular language to sort out how the “black technology” in this SUV works for you?
● 48V automotive electrical system voltage-the basis of advanced automotive electronic technology
Generally speaking, the standard voltages of vehicle electrical systems are mostly 12V and 24V. These two specifications are sufficient for general vehicle electrical appliances. The voltage value of part of the electrical system used on the Audi SQ7 this time is higher than the voltage of the general specification (up to 48V). What is the reason for this?
From an industry perspective, in order to more easily match various electronic parts, 12V or 24V automotive voltage standards have become an agreement between major car companies and electrical parts manufacturers. Just like three meals a day, it seems that people have become accustomed to this voltage value. And the higher voltage value does not mean that the traditional power supply system is insufficient in power supply, but because of efficiency and weight reduction considerations.
To put it relatively simple, this theoretical basis is based on the formula: power equals voltage multiplied by current (P=UI). When the current value is constant, the voltage can be increased to achieve high power output; or under the same power, the voltage can be increased to achieve a smaller current output and reduce the internal resistance of the wire. The useless work, and the smaller diameter wire can be used for power transmission, which achieves energy saving, high efficiency and weight reduction.
However, such inadvertent small changes are entirely possible to bring a revolution to the entire industry. The upgrade from 12V or 24V vehicle voltage to 48V seems to be a simple upgrade of the voltage. In fact, this simple upgrade has brought the upgrade of the electronic equipment in the entire car, making the once impossible possible.
Of course, such upgrades will also have some problems: 48V automotive electrical systems are to better match 48V electronic equipment, that is to say, for the current era of 12V or 24V automotive voltage, many electrical appliances need to be adjusted for this. In order to match the 48V vehicle voltage, the initial implementation strategy of the Audi SQ7 is to retain the vehicle electrical system on the original car, and realize part of the electrical functions by installing the 48V vehicle electrical system. In the future, if you want to fully realize the 48V automotive electrical system, it will inevitably cause a lot of cost investment to be used in the matching of various electrical appliances and coordination with accessory manufacturers.
On the other hand, compared with 12V and 24V voltage, 48V voltage is high-voltage power and has greater safety risks. Therefore, more measures need to be taken to compensate for this problem in terms of voltage protection. In this way, the development cost is also Go up.
● Active anti-roll bar-the gospel of medium and large SUV corners
Under normal circumstances, SUV models will increase the shock absorber and spring stroke (to achieve high passability), and reduce the damping of the shock absorber (that is, “use a softer suspension”, a wider range of motion, to ensure four wheels It can still touch the ground under complex road conditions) to ensure that the SUV has good trafficability in complex road conditions. But as a result, the center of gravity of the vehicle is increased, and when the vehicle suspension travel is long, the SUV model will have a large body roll when cornering at high speed, and the cornering stability is not as good as that of ordinary cars.
For sports-oriented SUV models, if you want to ensure good road handling, you must first solve the problem of its birth defects-a high center of gravity. In response to this situation, sports-oriented SUVs usually carry out a certain degree of suspension adjustment while ensuring passability, such as choosing relatively harder shock absorbers and relatively shorter springs, and some models to ensure better suspension. High-end suspension lateral support will adopt the method of replacing anti-roll bars. This is the case for the Audi SQ7, but the upgraded anti-roll bars of the SQ7 are different from those on ordinary cars.
In comparison, the traditional anti-roll bar only relies on the material and shape to restrain the anti-roll bar torsion caused by roll, and the restraining effect on the roll is limited, and the lateral support provided to the suspension is also limited, while the active type The anti-roll bar can apply reverse torsion force to actively improve the lateral support ability of the anti-roll bar, which is an advantage that the traditional anti-roll bar cannot. And in the absence of high lateral support requirements to ensure better comfort. However, because the structure is more complex and relies on 48V vehicle voltage, it is inferior to the traditional anti-roll bar structure in terms of cost and reliability.
● 4.0TDI “three supercharged” engine-the operation logic is complicated but the effect is remarkable
Now in this era of “turboization” of global car companies, a variety of turbochargers and their matching solutions abound, such as small inertia turbocharged engines and turbomachine hybrid turbocharged engines, etc., all at all times In the description of the arrival of the “turbine age”. The turbocharger can squeeze out more power output, this is undoubtedly, but compared with various competitors, Audi SQ7 chose a complex “three supercharge” program to optimize its engine performance. What is the working principle of this “three supercharged” engine? What is the meaning of “three supercharges”?
Indeed, if judged by just opening the hood, no one would think that this is an engine with advertised performance. This may be due to the auto show, and the iconic engine trim has not been installed. But when it comes to data performance, it will definitely surprise you.
|Audi SQ7 TDI|
|Number of cylinders||8|
|Fuel form||Diesel oil|
|Intake form||Twin turbocharging + electric turbocharging|
|Power per liter||110Ps/L|
|Official 0-100km/h acceleration||4.8s|
|Official comprehensive fuel consumption||7.4L/100km|
In the case of a single exhaust gas turbine, although the turbocharger can use the limited exhaust pressure to achieve a supercharge effect on the intake air, in a very low speed range, the exhaust gas turbine is affected by the exhaust back pressure, which does not increase significantly. At this time, electric turbine is needed to compensate; electric turbocharging can maintain a relatively stable speed at any time. Although the speed is not high, it has little effect when the engine is working at high speed, but it is used to supplement the low-speed intake pressure. , It is more than enough to make up for the lag problem of a single exhaust gas turbine at low speed.
In the middle speed range, the dual exhaust gas turbines in series can make good use of the exhaust gas for secondary supercharging to achieve high explosion; in the high speed range, the engine needs a large amount of air intake, and the solution of two exhaust gas turbines in parallel It just happens to cater to this working condition.
Audi's idea is to cooperate with each other in different speed ranges to maximize the advantages of each turbine, achieving a relatively linear high-torque output and high-speed high-horsepower.
In terms of structure, this engine uses a single-cylinder, two-intake valve and two-exhaust valve structure, which is the so-called “single-cylinder four-valve”, but the exhaust path guided by these two exhaust valves It is not directly integrated into the exhaust manifold as commonly seen, but independent of each other, and each is responsible for the operation of a set of exhaust gas turbines. In the case of single exhaust gas turbocharging, the engine only opens one exhaust valve to increase the exhaust pressure and push the single exhaust gas turbine to work under the same exhaust pressure, while the other set of exhaust valves does not open. Exhaust gas turbocharger 2 does not work.
Now that the second set of exhaust valves of the engine can be opened and closed, how is this implemented? We can see in the video that the AVS system in this engine is not the same as the Audi AVS system we are relatively familiar with. Although all functions are achieved by adjusting the camshaft, the AVS system of this engine is not used to adjust the valve lift, but is responsible for managing the opening and closing of the exhaust valve. In other words, the AVS system on the engine is a set of exhaust valve switches, so as to realize the intervention of the second set of exhaust turbines.
Although the turbocharger has many advantages, the major manufacturers have different strategies in terms of the problems caused by the structure of turbo lag. Audi’s strategy for this engine is to maximize the advantages of each turbine. Through complex logical structure and coordination, the engine has a smoother performance and high-level power output in each speed range. . But with such a complicated structure and working logic, we can't guarantee whether its reliability can reach the level of traditional engines. In this regard, it depends on Audi's ability.
The performance brought by the Audi SQ7 this time, to a large extent, is achieved by the automotive electrical system of the 48V on-board voltage. Based on the upgrade of this electric system, a “three-turbo” diesel engine and an active anti-roll bar have been developed to ensure the outstanding performance of the SQ7 in corners and straight lines. In the field of automotive electronics in the future, the 48V vehicle-mounted voltage standard will most likely become the mainstream and become the basic electronic platform support for many advanced technologies. This will change the limitations of 12V or 24V vehicle-mounted voltage in the field of automotive electronics.