The suspension improves the riding comfort and driving performance of the vehicle. EMS (Electronically-Modulated Suspension) and air suspension electronically control the damping force of the shock absorbers and air springs to further improve riding comfort and driving performance.
EMS is an abbreviation which stands for “Electronically- Modulated Suspension”. The size of the shock absorber orifice is changed so that the amount of oil flow is adjusted, causing the damping force to vary. The damping force is automatically controlled by the EMS ECU (electronic control unit) according to the selector switch condition and the driving condition. This ensures increased driving comfort and provided excellent driving stability. Diagnostic functions and a fail-safe function are also provided.
The air suspension uses an ECU to electronically control the suspension which uses air springs that utilize the elasticity of compressed air. There are also models that combine air suspension with EMS. The air suspension has the following features.
- The damping force can be changed.
- The spring rate and vehicle height can be changed by adjusting the air volume.
- Diagnostic functions and a fail-safe function are also provided.
The EMS & air suspension have the following features.
1. Mode change
(1) Damping mode select The damping force of the shock absorber can be changed from soft to firm.
(2) Height control (Air suspension only) The vehicle height setting can be changed from low to high. There are indicator lights that show the status for both the damping mode and the height control.
2. Damping force and spring rate control
(1) Anti-squat control
Changes damping force to firmer. This suppresses squatting during acceleration, thus minimizing changes in vehicle posture.
(2) Anti-roll control
Changes damping force to firmer. This suppresses rolling, thus minimizing changes in vehicle posture, providing excellent controllability.
(3) Anti-dive control
Changes damping force to firmer. This suppresses nose-diving during braking, thus minimizing changes in vehicle posture.
(4) High-speed control (normal mode only)
Changes damping force to firmer. This control provides the excellent driving stability and controllability at high speed.
(5) Shift-squat control (A/T vehicles only)
This limits the amount of rear-end squat when a vehicle with an automatic transmission first starts out. When the transmission shifted from the “N” or “P” range, the damping force is set to firm.
(6) Semi-active control
Smoothly changes the damping force to a target value in accordance with the changes in the road surface or driving conditions. Thus, excellent ride comfort has been realized while ensuring a high level of vibration damping performance.
Putting the vehicle in the sky-hook state constantly achieves a stable vehicle attitude in relation to the change of the road condition. In sky-hook EMS using this theory, the up and down motion of the body is sensed and a computer finely controls and adjusts the movement of the shock absorbers. This system greatly improves ride comfort and driving stability. In the latest models, such as the LS430, the semiactive control of the damping force control has been changed from sky-hook control to non-linear H_ control in order to effect even more fine control. As a result, excellent ride comfort has been realized.
3. Vehicle height control
(1) Auto-leveling control
Maintain vehicle height at a constant level regardless of the passenger and luggage weights. Operation of the height control switch changes the target vehicle height to “normal” or “high” level.
(2) High-speed control
Controls vehicle height to a lower side than the height selected by the height control switch (to lower position if “normal” is selected or to normal if “high” is selected) when the vehicle is driven at a prescribed speed or higher. This provides aerodynamics and excellent stability at high speed.
(3) Ignition switch-off control
Lowers vehicle height to target height when vehicle height becomes higher than target height due to a reduction in weight of passengers or luggage after ignition switch is turned off. This improves vehicle posture during parking.
Method to cancel the vehicle height control:
Before jacking up the vehicle or raising it on a hoist, make sure that the ignition switch is turned OFF.
If the vehicle must be raised with its engine running, jump terminals TD and EI of the TDCL or OPB and CG of the DLC3 (Data Link Connector 3) to stop the vehicle height control operation of the air suspension ECU.
For the vehicle with the height control ON/OFF switch, the switch is turned OFF.