Hyundai Equus: Description and Operation - Air Suspension System - Suspension System - Hyundai Equus VI 2009-2024 Service ManualHyundai Equus: Description and Operation

Active type ECS is applied and it includes the self leveling function.As shown in the picture, it consists of air spring, damper, reservoir tank, compressor (with dryer), solenoid valve block (pressure sensor embedded) and some other sensors.The vehicle height is controlled electronically by air pressure generated from the compressor and the damping force of shock absorber also is controlled independently by solenoid valve.The air spring is another type of spring that is becoming more popular on passenger cars, light trucks, and heavy trucks. The air spring is a rubber cylinder, filled with compressed air. If the vehicles level is required to change, a valve opens to add, or release air from the air spring. An onboard compressor supplies air. Be sure that these air springs does not function as a device to control damping force during driving (shock absorbing effect only) but mainly controls the vehicle height. And it offers the particularly constant level regardless of the vehicle weight.
Leveling Control
High Level :
In order to minimize the interference between the vehicle body and the road surface, the vehicle level is controlled by following two features.
Manual As long as the vehicle speed is lower than 70kph, possible to lift from normal to high level. Opposite manual operation (from high to normal) has no restriction for the vehicle speed.
Automatic If the vehicle speed exceeds 70kph with high level, it will be alternated into normal level automatically after 10sec for the safety.
Normal Level :
This is the basic level for normal driving condition. As same as high level, there are two features.
Manual Refer to the above High level.
Automatic If the vehicle speed exceeds 160kph with normal level, it will be alternated into low level after 10sec for the safety and better fuel consumption.
Low Level :
No manual operation is supported.
Automatic If the vehicle speed is lower than 80kph for more than 5sec, it will be alternated into normal mode automatically, however if it is lower than 40kph, it will be normal level immediately regardless of the time.Whenever the level is changed, there is a time delay between front and rear wheel for the safety. For lift, rear side will be advanced and front side will be lifted later on. For lowering, it is opposite.(Because of this operating sequence, there may be a noise if the brake (AVH, EPB) is being engaged while level control)

The closed loop has some merit comparing with the open loop type.
In case of open loop type, system intakes the air from atmosphere and compresses it whenever necessary, therefore the system response time (leveling control time) is long.
However in case of close loop type, the high pressure is stored in the reservoir tank in ordinary time and used whenever necessary, therefore the response time reduces dramatically. Of course even close loop system also does intake and exhaust for the supplementary filling of air, dryer regeneration accordingly but the actual air amount is very low.
System Air Filling

This job should be done whenever the system components were replaced with new one (except the electrical sensor or control module). Using air filling machine, supply the air to the air filling valve offered in the LH side of engine room. Air will flow to reservoir tank, compressor and will arrive in the air springs.
- Due to the length of air tube and location, at first the front air spring is fulfilled and the rear air spring will be completed later on.
- The vehicle has to be lifted up. (The air spring (rubber) may be bent if the air spring was empty when the system filling starts)
- IG ON and the particular mode in the scanner are required but engine starting is not necessary.
(Refer to the section of System air filling procedure for more detail information)
- While the system air filling, the compressor (built in vehicle) does not operate.
- There are two kinds of air filling :
System air filling: the external air pressure is supplied at the factory or workshop (1 time) the vehicle compressor does not operate. It is not possible to do this filling by vehicle compressor. The overload of compressor must be avoided and furthermore, the vehicle compressor will not operate if the air pressure (volume) is too low. (Less than 80 ~ 120 bar-liter)Garage air filling (Supplementary filling): whenever the supplemental air is required in the system, the air is filled by the vehicle compressor.
Depending on the capacity and the pressure of the air filling machine, the whole time to complete differs but mostly it takes around 50 sec.
The target air pressure level at each component is :
- Front air spring: around 7.5bar, Rear air spring: around 8.5bar, Reservoir: around 9~10bar.However, it may change with a little amount in the case of air spring depending on the weight of vehicle (passenger & baggage)
Lifting Level

By operating the compressor, the compressed air inside reservoir tank will be moved into the air spring via solenoid valve block in order to lift up the vehicle height. During lifting mode, the air does not pass the dryer as shown in the picture. The front rear springs are lifted at first and then front springs are followed when lift the vehicle. The reason is to reduce the air resistance while driving and avoid giving an excessive headlamp beam to the driver in opposite direction lane on the road for the safety.
Lowering Level

Whenever lowering the vehicle, the dryness is accomplished by flow the air through dryer as shown in the picture. The reverse valve and air spring valves are open so that the compressed air comes out from the air spring. At the same time, the compressor is operated so that the air passes through the dryer in order to store dried air into the reservoir tank. Be sure that even during the process of lowering, the compressor will operate in normal condition (as long as the compressor and compressor relay is normal).
Of course, if the compressor or compressor relay is failed, the lowering (down-leveling) is available by operating the ambient valve (No. 7 in the picture) only like a process of air discharge but this is done only in case of emergency condition.
For example, the vehicle is running with high level and the compressor (or relay) failure is detected, if the vehicle speed is higher than 70kph for 10sec or more, the vehicle height should be lowered to normal level by ambient valve for the safety and lower fuel consumption.
Air Filling (Supplementary)

If the air mass inside the system is less than 93 bar-liter (refer to the concept of bar-liter in the page of current data in this manual), the air is added by the compressor in the vehicle. At this time the air passes through the dryer as shown in the picture so that the dry air can be supplied into the system. Mostly this may happen in case of long time parking.
Air Discharge (Regeneration)

The purpose of doing air discharge is normally to regenerate the air dryer built in the compressor. The discharged air amount is very small.
The independent logic to perform air discharge is implemented to decide the regeneration period based on the following factors. (Not performed every ignition cycle)
- Air pressure sensor (built in the compressor) signal
- Height sensor signal
- Engine room temperature
Not only for dryer regeneration but also for other reason, sometimes it is necessary to discharge the air from the system. Scanner offers the Air discharge mode to cope with this time, and just enter to the above mode and perform the air discharge. Sometimes, air discharging is required to inspect the noise from the rear chassis frame or front suspension. Scanner will control the reverse valve and five solenoid valves in the solenoid block in order to discharge the air electrically.
Be sure that this menu in the scanner does not offer the discharge of air in the reservoir tank as follows.
From solenoid valve block to air filter (mostly air in the air springs):
The air in this area can be discharged by the scanner (electrically)
Air in the reservoir cannot be discharged by electrical driving of solenoid valve in the scanner.
Instead, you can disconnect the air tube between the compressor and reservoir tank manually.
Then only the air in the tank will be discharged as long as the air in the air springs is closed by the solenoid valves.
This means that the vehicle will not be rapidly lowered even if the mentioned tube is disconnected. However, disconnect the tube gently because the air will come out rapidly.
    Components and Components Location
    Components Location 1. Compressor2. Air tank3. Air tube4. ECU5. Rear CDC Damper6. Rear spring7. Front air strut assembly8. G-Sensor9. Height sensor ...

    Repair procedures
    Air Injection Procedure     When injecting air into the air suspension system, always raise the vehicle off the ground using a lift to prevent potential damage to the ai ...

    See also:

    Components and Components Location
    Components 1. Rear bumper cover2. Rear bumper side bracket [LH] ...

    Engine Coolant Temperature Sensor (ECTS) Schematic Diagrams
    Circuit Diagram ...

    Front Strut Assembly Components and Components Location
    Components 1. Insulator cap2. Insulator assembly3. Spring upper pad4. Dust cover 5. Bump stopper6. Coil spring7. Spring lower pad8. Shock absorber ...


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