On April 10 this year, BYD released the much-anticipated YunNian technology. However, many people’s attention to Yunnian technology is more focused on Yunnian-P equipped with a hydraulic system, such as the U8 model. In the following period, almost everyone equated Yunnian-P, which uses a hydraulic system, with BYD’s Yunnian technology, but did not realize that Yunnian is just a trademark of BYD’s smart suspension, not an independent suspension. system technology.
Currently, BYD’s Yunnian brand family has three Yunnian suspension technologies on the market. The first is yunnian-C, which uses CDC (continuously controlled damping) and coil springs; the second is yunnian-A, which uses air springs and CDC; and finally the yunnian-P, which is equipped with the yunnian U8 and Equation Leopard 5 yunnian The flagship version uses a hydraulic system. Therefore, just like Porsche’s PDK, BMW’s xDrive and Audi’s quattro, although BYD’s suspension systems are all called “Yun Nian”, they are very different in their technical routes and implementation effects. Next we’ll explore in detail how they differ and how effective they are.
Yun Nian-P: Camping Leveling Mode
Let’s first take a look at yunnian-P. This vehicle uses a hydraulic system. In the official promotion, the biggest advantage of yunnian-P is its ultra-long suspension adjustment stroke. Compared with the adjustment range of about 90-140mm for ordinary chassis lift models, the Yangwang U8 equipped with yunnian-P can achieve a maximum suspension adjustment stroke of 200mm. This allows it to have a maximum ground clearance of 310mm, and also provides a very practical camping leveling function, which is very suitable for outdoor travel and camping parking.
However, in order to achieve the suspension travel adjustment of up to 200mm, yunnian-P did not use traditional air springs as a component to adjust the vehicle’s ground clearance, but chose a hydraulic suspension system. This system adjusts the suspension by adjusting the internal hydraulic oil volume and changing the length of the shock absorber tube. This design allows yunnian-P to have a very impressive adjustment speed. Whether it is raising or lowering, the overall speed is significantly faster than the traditional system that uses an air pump to inflate and deflate the air suspension. Especially in terms of lowering the height of the vehicle, it only takes less than 2 seconds to lower the vehicle instantly. However, precisely because of this design, the use experience of yunnian-P is somewhat different from that of traditional suspension systems.
As we all know, the height of a modified vehicle is usually achieved by changing the length or position of the springs, such as modified short springs, coilover shock absorbers or original air suspension. Springs play a role in supporting the vehicle body in the vehicle’s suspension system, so using springs to change the height of the vehicle body is the most convenient method. However, the yunnian-P uses a different way to adjust the height of the vehicle, using oil in a hydraulic shock absorber paired with traditional coil springs. Helical springs have a characteristic, that is, when the length remains unchanged, the more the spring stretches, the lower the support force; conversely, the more the spring compresses, the higher the support force.
This means that when yunnian-P changes the height of the vehicle body, the tension and compression of the coil springs will also change, thus affecting the vehicle’s support performance. For example, when the vehicle is in its lowest position, the coil springs are greatly compressed, thereby increasing support. When the suspension is in a higher state, the support provided by the stretched springs will be greatly reduced. Therefore, in order to maintain ground clearance while adjusting the height, vehicles equipped with yunnian-P system do not rely entirely on springs to support the body, hydraulic shock absorbers will also participate. As the height of the vehicle increases, the proportion of hydraulic shock absorbers participating in supporting the body will also increase.
However, we all know that the shock absorber can only provide a damping effect and does not have any supporting force in a stationary state. The oil in the shock absorber tube will flow to another chamber through the small hole that provides damping, causing the vehicle to gradually sink until the coil spring is compressed enough to support the body. If the small hole inside is closed, according to the principle of incompressibility of liquids, the shock absorber tube will lose its compression ability, similar to a wooden stick. In order to solve this problem, the yunnian-P system is not only a hydraulic shock absorber, but also a hydro-pneumatic shock absorption system. The oil does not completely fill the internal pipelines, coexists with the gas, and is connected to several pool-like accumulators at the rear, which together form the yunnian-P’s shock absorption system. The incompressible oil is responsible for height adjustment and damping, while the easily compressible gas provides support and cushioning, thus solving the previously mentioned problems.
Just like multi-chamber air suspension can change the spring stiffness, yunnian-P’s hydro-pneumatic suspension system can also adjust the overall suspension stiffness by turning multiple accumulators on or off. The more accumulator connections, the greater the internal volume and the lower the suspension stiffness; the fewer accumulator connections, the higher the stiffness. Therefore, the yunnian-P system equipped with the U8 can automatically provide three different suspension stiffnesses based on sensor data and driving modes: a medium-hard first-level stiffness, a softer second-level stiffness, and a softer third-level stiffness. This design enables yunnian-P to provide appropriate suspension adjustment under different road conditions and driving needs, improving the vehicle’s driving comfort and stability.
In general, the yunnian-P system uses a combination of hydraulic shock absorbers and coil springs to adjust the height of the vehicle and change the suspension stiffness by adjusting the oil in the hydraulic shock absorbers and the connected accumulator. This design allows yunnian-P to provide appropriate support and damping while maintaining ground clearance to provide a comfortable driving experience.
Although when negotiating potholes at high speeds, the U8’s suspension may feel a little stiff when looking up. However, when negotiating potholes at low speeds, I found that the car’s suspension exhibited an indescribable softness. Not only can it compress or stretch quickly to ensure that the tires stick to the ground, but there is almost no body shaking when the axle loads of the left and right suspensions change. This is mainly due to the four-wheel linkage module equipped with U8.
When a wheel on one side is compressed, the four-wheel linkage module of the yunnian-P system will quickly balance the compressed oil to the stretched wheel on the other side. Therefore, within the suspension travel range, the coil springs and internal air chambers responsible for supporting the body require almost no deformation, and all energy can be absorbed and transferred through internal oil pressure, providing a smooth low-speed off-road feel.
Talking about the dynamic driving experience on paved roads, as we all know, the U8 weighs an astonishing 3.5 tons, so its road handling has always been questioned. However, in actual driving, it has to be said that the yunnian-P system provides a lot of help in this regard. It uses roll compensation to allow the driver to almost not feel roll when cornering, and has excellent support performance. Coupled with the extensive vector torque adjustment of the four-wheel independent motors, the driving of the U8 ultimately feels more like an urban SUV weighing less than 2 tons.
yunnian-A: Intelligent air body control system
After the complex Yun Nian-P, let’s discuss the simpler Yun Nian-A. In fact, you can understand “Yunchai-A” as “Yunchai-Air”, because A represents air. Currently, yunnian-A is used in the Denza N7 model for the first time, and like most air suspensions, it realizes the adjustment of the body’s ground clearance and continuous damping through a combination of air springs and continuously variable damping (CDC).
During the actual driving of the N7, yunnian-A performed very well. In Comfort and Eco modes, the CDC and air springs match very well and can effectively absorb vibrations. And when I adjusted the vehicle to sport mode, the stiffer damping provided quite good support. In addition, thanks to the iCCT intelligent comfort control system, the vehicle’s longitudinal tilt performance has also been significantly improved during strong acceleration and braking. At the moment of violent acceleration, I can only feel the push-back feeling caused by inertia, rather than the upward feeling caused by the compression of the rear suspension.
However, it should be noted that the current yunnian-A of Denza N7 is only the entry-level version, and the air spring matching the CDC is only a basic single-cavity structure. This means that in terms of overall suspension stiffness, the shock absorber damping is mainly adjusted through CDC, and the effect is not as layered as the air spring with a dual-cavity structure. However, in future BYD models, the yunnian-A system equipped with dual-chamber air springs will appear. Officials said that in the hardest state of the yunnian-A system using a dual-cavity structure, the changes in soft and hard stiffness will be more obvious, greatly improving the subjective control experience.
yunnian-C: Intelligent damping body control system
Just like yunnian-A represents air, the letter C in yunnian-C represents continuously variable damping (CDC). Different suspension feelings can be achieved by adjusting the damping of the shock absorber. Compared with yunnian-A, yunnian-C can not only significantly reduce costs, but also the linear coil spring support force changes will make the driver feel more realistic. In fact, even expensive supercars mostly use a combination of coil springs and continuously variable damping.
Since the cost of the yunnian-C system is significantly lower, it is suitable for more models than yunnian-A and yunnian-P. At present, BYD’s Song L, Han, Tang, and Denza’s N8 and D9 are equipped with the yunnian-C system with continuously variable damping. Users can adjust the yunnian-C mode in the car through the car.
Taking the Han DM-p Ares version I experienced as an example, in comfort mode, the vehicle performance is slightly lacking in damping. When passing through potholes or raised road surfaces, the vehicle will not completely eliminate the impact at once, but will gradually weaken the spring compression. The energy generated causes the vehicle to undergo multiple gradually decreasing undulations, eventually reaching a completely stable state. Although this performance is not outstanding by automotive engineering standards, for ordinary consumers who do not know much about automotive engineering, this shock absorption effect is considered comfortable, especially for rear passengers. Let’s talk.
When I adjusted the vehicle’s yunnian-C system to sports mode, the car actually showed a certain sense of movement. When the vehicle passes through undulating roads and is thrown up to a certain extent, the suspension system will produce a significant damping sensation to stabilize the vehicle and prevent it from being thrown up too much. When the vehicle presses down after passing through the bumps on the road, the shock absorber can quickly release the energy of the spring and is very sensitive. In addition, the vehicle’s low-speed compression damping is also very good. Even if I accelerate a little on the mountain roads in yunnian, I won’t lack the same confidence as when I drove the BYD Han two years ago.
In the context of the electric era, Chinese car companies finally have the opportunity to achieve transcendence after getting rid of the two manufacturing difficulties of engines and gearboxes. However, in the field of chassis suspension, Chinese car companies have always been restricted by foreign suppliers. However, BYD, the leader of China’s new energy vehicles, stepped forward and launched its independently developed yunnian system to support domestic suppliers and break the monopoly that existed for many years. In the near future, the yunnian-X mounted on the U9 will be unveiled. As a keen track enthusiast, I am very much looking forward to the control performance of the yunnian-X!