BYD Dolphin abandons the plate suspension, the new chassis is like a Golf, and the comfort exceeds that of the Corolla?

(The picture shows the old BYD Dolphin)

The guide price of BYD Dolphin is within 100,000 yuan, which is not a surprise enough. As a pure electric small car, the BYD Dolphin Glory Edition directly replaces the torsion beam non-independent rear suspension of the old model with a four-link independent suspension. Changes in the suspension structure certainly help to increase the car's handling limits. With the 100,000 yuan level of small cars, the independent suspension of the whole car began to be replaced. Does this mean that independent suspension is no longer a "luxury"?

At the 100,000 yuan level, it is not difficult to use independent suspension?

The independent suspension seems to be tall, to a large extent, because the user combines the independent suspension with the front double wishbone + rear multi-link, and directly draws the equal sign. But in fact, there are many types of independent suspensions, in which the differences and effects are also quite large. Taking the front suspension that everyone is more familiar with as an example, the frequent customers of models within 200,000 yuan, MacPherson suspension, obviously cannot compete with the double wishbone in terms of cost, handling and stability. As for the case with the rear suspension, it's a bit more complicated.

Since the rear axle of the car does not have a steering function, and in the era of fuel vehicles, the power system is loaded on the front axle in most cases. Therefore, the empty rear axle part can even directly adopt a through-type connection structure such as a torsion beam. Coupled with the diversified needs of vehicles, the advantages of non-independent suspension in terms of load capacity are further amplified. Loading artifacts such as leaf springs have also been greatly developed.

Returning to the independent suspension category, a five-link is certainly the most ideal situation. Because from the perspective of force, it has taken care of every aspect as much as possible. All that's left is to test the tuning, materials, and matching shock absorbers, springs, and even air suspension. However, just looking at the manufacturing cost and tuning difficulty, it is already destined to be a five-link rear suspension structure, which is not conducive to the popularization of automobile products within 200,000 yuan. The solution is to reduce the connecting rod.

When it comes to cutting the connecting rods, it is not directly removing one or several connecting rods on the basis of the five connecting rods. Instead, fewer connections are used, and all force directions are still taken care of. At the same time, it saves manufacturing costs and lowers the threshold for tuning. Let's talk about the front suspension structure, if the five-link rear suspension can be seen as a variant of the double wishbone front suspension. Then the three-link rear suspension (also known as the "chopsticks suspension") can be seen as a MacPherson rear axle variant. The latter is essentially a MacPherson suspension of the lower A arm, split into two connecting rods, and then cooperate with a longitudinal tie rod to form a three-link form.

The four-link structure used by the BYD Dolphin Glory Edition, just from the quantitative point of view, can be judged as a compromise between three links and five links. In fact, this is also the case, the so-called four-link rear suspension, which can be seen as a youth version of the rear axle variant of the front double wishbone suspension. In other words, the source of technology is still a double wishbone, not a magic change MacPherson. Specifically, a four-link rear suspension is generally designed with three transverse links and a trailing arm. Therefore, it is also called the "E-type multi-link" structure, and broadly speaking, Volkswagen's classic PQ35 platform, as well as most models in the current Toyota TNGA architecture, the rear suspension can be included in this category.

Compared with the full-blooded version of the five-link structure, the four-link (E-type multi-link) theoretically sacrifices the control of the horizontal axis, and as for the pitch control, it can be supplemented by the thick trailing arm. To put it simply, the priority is still on comfort, followed by cornering stance and control of the vehicle in continuous motion. Of course, these are just theories. Models that use this suspension structure also have products that focus on sports tuning, such as the sixth-generation Volkswagen Golf. Returning to the BYD Dolphin, standing in its positioning and price range, switching to a four-link rear suspension is undoubtedly praised.

The chassis scheme of the BYD Dolphin is not suitable for all cars?

Since the four-link link is so balanced and easy to use, and in terms of cost, even the BYD Dolphin at the level of 100,000 yuan can be adapted. So can most passenger cars start with a four-link rear suspension? The answer is not necessarily. The core contradiction lies in the fact that the layout structure of E-type multi-link occupies too much horizontal space. A casual picture of the chassis of a model with this structure can be found that the lower swing arms on both sides and the connection with the subframe basically do not allow the rear axle position to add other large parts.

In the context of electrification, the most easily configured large part of the rear axle is the electric motor. In fact, this design has locked in the potential of the high-horsepower rear motor designed by Toyota HEV models under the TNGA architecture, thus realizing the potential of high-quality electric four-wheel drive. As a result, Toyota can only upgrade the rear axle on a small number of mid-to-high-end models, risking pushing up costs. In the same way, when Volkswagen designed the MEB pure electric platform, it directly replaced the five-link rear suspension, which fundamentally lifted the space restriction on the rear axle motor. As for the BYD Dolphin, it is already a front-motor model, so you don't have to care about the space layout of the rear axle at all.

So, this also answers another puzzling old question in disguise. That is, why there is still a market for "chopstick suspension". In order to better adapt to the rear axle motor, the non-independent suspension was not taken into account from the outset. In the field of independent suspension, it is good to use five links directly in one step. However, if the positioning of the model has been very clearly locked in the dimensions of space and comfort, the five-link link will have both limitations and a bit uneconomical. Then, the four-link structure that takes a step back also does not fit. In the end, I had to take a step back and switch to the three-link type. You know, the MacPherson suspension was born because of its high degree of space friendliness. Its variant of the three-link suspension, only on the rear axle, replicates the advantages of its predecessors again.

Therefore, for front-wheel drive electric vehicles such as the BYD Dolphin, it is better to use a torsion beam directly than a three-link rear suspension. Anyway, the rear axle is yours, and it is directly space, practicality as the first priority, and even a certain loading capacity can be taken into account, and the cost is saved, so why not. Nowadays, new cars have to have a higher pursuit of comfort and handling. Then the four-link becomes the optimal solution for the BYD dolphin. And this job, it is true that not all models can be simply copied.

To sum up: front-wheel drive electric vehicles either continue to adhere to non-independent rear suspension such as torsion beams, or directly replace the four-link (E-type multi-link) rear suspension to improve the driving quality. And products that require a rear motor, or the platform itself locks up the rear suspension space. Then the model that pursues comfort and large space does not need to have a psychological burden when it is adapted to a three-link rear suspension (chopstick suspension). Five links are good, but in the end it's a matter of trade-offs. Of course, the BYD Dolphin has set an example on the chassis at the 100,000 yuan level. Perhaps in the average passenger car at this price, the non-independent rear suspension is indeed going to fall out of favor.