It's been more than two years since I last skied, and the pandemic has changed a lot of things. Nowadays, only every weekend, I can only occasionally see photos of northern friends skiing in the circle of friends.
In the past, every snow season, Audi quatto will appear in Changbai Mountain, BMW, AMG, Porsche will appear in Yakeshi, and even Bentley is planning the first domestic ice and snow test drive this year.
However, the epidemic at the beginning of this year has disrupted many test drive plans.
Well, even without talking about ice and snow test drives, we can talk about four-wheel drive technology. What kind of four-wheel drive has the best grip on ice and snow roads?
As soon as I talk about the four-wheel drive, I know that many friends think of "ability to get out of trouble", "cross axis" and so on. Four-wheel drive will certainly have better off-road passability than two-wheel drive models, but not all four-wheel drive is designed for off-road capabilities.
For example, the familiar BMW M3 has always been a representative of rear-drive performance, but the new generation of M3 provides M xDrive four-wheel drive models in addition to the rear-drive. Even though the four-wheel drive version is heavier, the 100-kilometer acceleration is still 0.4 seconds faster than the rear drive.
Therefore, the greater purpose of the four-wheel drive of the road model is to improve the grip of the tires, especially on the slippery, snowy road surface, which has a huge advantage that the two-wheel drive model cannot match.
The father of GT-R, Mizuno Andtoshi, once said to us personally: Everyone thinks that the speed of improvement is based on lightweight, but in fact, the direction is wrong. The most effective way to increase speed is to maintain four rounds of grip. Therefore, even if the GT-R sacrifices weight, it must be equipped with a very complex four-wheel drive system.
Let's look back at how the originator of on-highway 4WD technology, the Audi quattro, became famous in the first world.
In 1977, Audi engineers discovered that the four-wheel drive system had amazing handling performance on curves and ice and snow roads, so they decided to transplant the four-wheel drive system to The Audi mass-produced civilian sedan, so they had the quattro, which is known as the cornerstone of Audi's four-wheel drive technology.
Veteran fans may remember an advertisement that in 1986, an Audi 100 CS quattro successfully boarded the 37.5-degree Pitk vuori ski jump in Finland. This fully demonstrates the strong traction brought by Audi quattro technology.
So what kind of four-wheel drive has the best grip on ice and snow roads? Only fast is not broken.
Unlike hardcore off-roaders, which emphasize torque output, even if the tires slip, it doesn't matter if the four-wheel drive. The key points of highway high-speed four-wheel drive technology are the speed of response and the instantaneous deployment of four different grips.
The quattro full-time all-wheel drive system with pure mechanical central differential, the cornerstone of quattro technology, is now only available on high-performance Audi models with longitudinal platforms, Tiptronic gearboxes, such as audi RS6, RS4 and so on.
The purely mechanical torque self-locking central differential is the heart of this quattro full-time four-wheel drive, which innovatively uses a lightweight hollow shaft to transmit power and achieve zero delay distribution of torque. This is also the secret of audiquattro speed.
Even the vehicle's torque is transferred from the skidding axle to the adhesion side, and under extreme conditions, up to 70% of the torque can be transmitted to the front axle, or up to 85% of the torque can be transmitted to the rear axle.
For high-performance models, a complex set of mechanical four-wheel drive is indeed very necessary. But for ordinary models that are driven daily, four-wheel drive also brings side effects: on the one hand, the mechanical resistance of four-wheel drive will bring about an increase in fuel consumption, and on the other hand, it will increase the weight of the car.
Therefore, lightweight, electronic, especially the "disconnectable" four-wheel drive system has become the development direction of daily driving models.
In 2016, AutoLab test-drove a new all-wheel drive system in Frankfurt, Germany – the key technology is that the multi-plate clutch will disconnect the power transmitted to the rear wheels, while the rear electronically controlled tooth-mounted coupler will also be disconnected, so that the drive shaft remains truly stationary, further reducing energy losses.
Later we learned that this was the introduction of the quattro ultra intelligent all-wheel drive system later in 2016.
Quattro ultra When the vehicle is in a low-load situation such as cruising, the system switches to front-wheel drive mode, and because the rotating shaft is completely disconnected, it has the same low fuel consumption as the front-drive car. When the vehicle is starting, climbing and driving intensely, it instantly switches to all-wheel drive mode.
Unlike ordinary timely quad drives, the quattro ultra is a pre-judgment four-wheel drive, and its speed is basically indistinguishable from pure mechanical quattro. The benefits are that the average fuel consumption per 100 kilometers has been reduced by 0.3 liters, and the entire four-wheel drive system has lost 4 kilograms of weight.
Is it better to drive, drive or drive? This issue has been debated for over the past two decades, but now it is clear that the four-wheel drive has prevailed.
On the one hand, the performance of vehicles is getting stronger and stronger, and more and more high-performance models such as BMW M3 and M5 have to use four-wheel drive. But the bigger direction is electrification — electric motors can create more powerful four-wheel drive, while cost and energy consumption are getting lower and lower.
In the era of electrification, the Audi quattro is preceded by "e" - there is no rigid connection in the traditional sense between the front and rear axles, but instead the front and rear axles are freely distributed by electronic control, and the torque distribution ratio can be from 0 to 100%.
The strength of the motor, on the one hand, the power distribution of the front and rear wheels is completely decoupled, and the range of differences in the driving characteristics of the vehicle in different driving modes is greatly improved. In dynamic driving mode, for example, the vehicle's torque is more biased towards the rear axle, or only one motor can be activated to achieve optimal energy consumption.
In the case of the e-quattro, for example, a powerful on-board computer continuously and precisely adjusts the ideal torque distribution between the front and rear axles at a rate of 200 times per second. At the same time, the motor also has a response speed of 4 times that of mechanical four-wheel drive, and it takes only about 30 milliseconds from detecting adhesion changes to adjusting the optimal torque distribution.
This is the secret of a powerful set of highway four-wheel drive - the world's martial arts, only fast is not broken.