China Passenger Car Electronic Control Suspension Industry Research Report, 2025

Electronic control suspension research: air springs evolve from single chamber to dual chambers, CDC evolves from single valve to dual valves

ResearchInChina released China Passenger Car Electronic Control Suspension Industry Research Report, 2025, which sorted out the relevant dynamics of OEMs and suppliers in the field of electronic control suspension in the past year, and analyzed the technical characteristics of their electronic control suspension products.

Since 2023, the installation volume of electronic control suspension in passenger car market has steadily increased. Taking air suspension as an example, in 2024, the installation volume exceeded 800,000 vehicles, a year-on-year increase of 38%.

In addition to the performance in the amount of installation volume, the development of front-mounted electronic control suspension of Chinese passenger cars also has many highlights in technology iteration, including the application of dual-chamber air springs, the replacement of electronic shock absorbers with linear motors, the installation of fully active hydraulic electronic shock absorbers, and the first installation of dual-chamber dual-valve suspension of domestic models.

1. Iteration of air springs from single chamber to dual chamber

The dual-chamber air spring has two chambers, the main chamber and the auxiliary chamber, and the on-off of the two chambers is controlled by solenoid valve. Compared with the mutual influence of stiffness control and vehicle height adjustment of single-chamber air spring, dual-chamber air spring realizes the decoupling of stiffness and height. The main advantages of dual-chamber air spring over single-chamber air spring are:

① The system can have two stiffness modes. The dual-chamber air spring controls the connection and isolation of the main and auxiliary air chambers through the solenoid valve to achieve multi-level stiffness adjustment. When the auxiliary chamber is opened, the air chamber volume increases and the stiffness decreases; when the auxiliary chamber is closed, only the main chamber works and the stiffness increases. The difference in stiffness between the two modes is 40%~50%. This design allows the vehicle to switch flexibly between comfort mode and sports mode. Taking the dual-chamber air suspension of Li Auto as an example, two driving styles, comfort magic carpet and sports magic carpet, are provided in the central control screen suspension settings for users to choose.
Faster stiffness adjustment speed. The dual-chamber solenoid valve can switch the air chamber state within 0.1 seconds to achieve instantaneous stiffness adjustment. Compared with the single-chamber air spring, its response speed is about seconds.
Stiffness adjustment is decoupled from vehicle height adjustment. The height of the vehicle body remains unchanged when adjusting the hardness and softness of the suspension.

The dual-chamber air spring is more in line with the requirements of new energy vehicles for handling and comfort. In the past year, many new energy models including Xpeng G9, Xpeng X9, and Li L9 have chosen to be equipped with dual-chamber air springs.

2. Dual-valve CDC shock absorber installed on independent brands

The two solenoid valves of the dual-valve CDC control the oil flow rate during compression and stretching respectively, decoupling the damping adjustment of compression and stretching, with faster response speed and larger damping adjustment range. The traditional single-valve CDC uses one solenoid valve to control compression and stretching damping, and the two affect each other.

Take the dual-valve shock absorber equipped with the renewed Li L9 as an example. Switching from a single valve to a dual valve, the damping force of the suspension system is increased by up to 50%. In addition to ensuring sportiness and comfort, it further optimizes pitch and roll performance. With the dual-chamber air spring, the driving performance of the renewed Li L9 is optimized as follows (compared with the 2024 Li L9 dual-chamber single-valve suspension):
① The head-up and braking nodding are reduced by 12%; The turning roll is reduced by 24%; ③ The body ups and downs of the flying slope are reduced by 19.5%; the renewed Li L9 is also the first mass-produced model to adopt a dual-valve CDC + dual-chamber air spring suspension combination.

In November 2024, the fully active suspension in Xiaomi Intelligent Chassis Pre-research Technology released by Xiaomi also uses a combination of dual-chamber air springs + dual-valve CDC. According to information released by Xiaomi, the maximum lifting force of the fully active suspension exceeds 44,400N, the suspension adjustment range can reach up to 140mm, and the adjustment speed reaches 100 times that of the air spring.

3. New gameplay of fully active suspension

Traditional fully active suspension generally uses a hydraulic system with air springs, such as Porsche's Porsche Active Ride (PAR for short). PAR integrates two sets of hydraulic pumps and their control units, and a deceleration mechanism in each active suspension hydraulic pump assembly. Each system is used for the shock absorber on one wheel, so that the four-wheel suspension can be actively and independently adjusted.

NIO ET9, which was launched in December 2024, also uses a hydraulic fully active suspension. Each shock absorber is highly integrated with an independent electric hydraulic pump and a brushless DC motor. The product was jointly developed by NIO and Clearmotion. According to NIO's actual test data, the application of the above-mentioned fully active suspension allows NIO ET9 to perform well in the following driving scenarios:

1. ET9 can accelerate and start and brake at various speeds of 80-120km/h without nodding or raising its head, so that the body always maintains a nearly horizontal posture
2. At a speed of 60km/h, it can quickly drive over asymmetric continuous undulating roads, which can effectively suppress the body from swinging sharply on asymmetric undulating roads
3. At a speed of 80km/h, it can drive over uphill and downhill slopes with a drop of 30cm. When going uphill, the fully active suspension applies the main force to pull down the front of the car to avoid being lifted up by the slope. At the same time, the rear suspension applies the main force to lift the rear of the car to keep the body posture stable; when going downhill, the Tianxing fully active suspension applies the main force to support the body, and then slowly releases it
4. At a speed of 15km/h, lift the champagne tower over continuous speed bumps. Actively control the suspension journey in the continuous speed bump scenario, so that the wheels can run in line with the speed bump to prevent the body from swaying left and right

In the suspension compression stroke, the fully active suspension of NIO ET9 converts kinetic energy into electrical energy through a hydraulic pump, and can generate up to 5kW of energy recovery.

In addition to the hydraulic solution, BYD has mass-produced and applied a solution that uses motor vibration reduction - Yunnian-Z. Yunnian-Z replaces traditional shock absorbers with linear motors and is equipped with air springs. Also, because the motor has the functions of both working and generating electricity, Yunnian-Z can also achieve energy recovery in the suspension compression stroke.

From the data, the full-link execution time of Yunnian-Z is only 5ms, the body adjustment accuracy is only 1mm, and the adjustment speed can reach 500mm/s. The peak power of the four motors plus system reaches 50kW.

From the perspective of vehicle driving performance, the main improvements of Yangwang U7 equipped with Yunnian-Z include:
1. When the vehicle accelerates and decelerates rapidly from 0 to 100 km/h, the pitch angle can be less than 0.5°, and the user can hardly feel the pitch
2. The negative roll angle function that the maximum angle when turning is -2° effectively improves the roll feeling caused by inertia when cornering
3. When the vehicle is driving at high speed, passes through the road-bridge connection, it is easy to cause a jump due to the change in road slope. Yunnian-Z can pull the body at one time to achieve a zero-throw jump in the sense of body
4. Yunnian-Z can also achieve active defense capabilities. When the vehicle encounters a side collision, the body is instantly lifted on one side to transfer the collision to the area with higher body strength to ensure driving safety

In the past year, the technical iteration of electronic control suspension in key components such as shock absorbers and air springs has shown a multi-point blossoming development pattern. It is expected that more fully active suspensions will be installed in the next one to two years, further improving the penetration rate of electronic control suspensions.