The new lexus gs 2012: driving dynamics
• Rigid bodyshell and new suspension for optimum agility and stability with superb ride comfort
• Adaptive Variable Suspension (AVS) to further enhance ride quality, stability, body control and steering response
• Powerful brakes for enhanced stopping power and control
• Drive Mode Select function for a choice of ECO, NORMAL, SPORT S and SPORT S+ driving modes, and manual paddle shift override
• GS 450h F SPORT also available with the Lexus Dynamic Handling system - an integrated four-wheel steering system for sharper response and greater agility
• Lexus Dynamic Handling system - the world's first hybrid vehicle integration of Dynamic Rear Steering (DRS), Variable Gear Ratio Steering (VGRS) and Electric Power Steering (EPS)
The new GS has been designed to offer customers a much more engaging and pleasurable driving experience. It combines sharp, responsive steering and excellent body control with outstanding high speed stability and all the ride comfort expected from a Lexus performance sedan.
The significant improvements to the next generation GS's driving dynamics have been achieved on three levels:
- A re-engineered bodyshell with a 14% increase in rigidity, new suspension to promote optimum agility and stability whilst maintaining ride comfort, and more powerful brakes for enhanced stopping power and control.
- Adaptive Variable Suspension (AVS) to further enhance ride quality, stability, body control and steering response.
- The Lexus Dynamic Handling system; leading edge platform technology which offers the world's first integration of Dynamic Rear Steering (DRS), Variable Gear Ratio Steering (VGRS) and Electric Power Steering (EPS), to coordinate every aspect of front and rear wheel control and provide agile, sharp and confident driving behaviour with a more direct response to the driver's actions.
Extensive computer aided design has been used to optimise body rigidity, ensuring precise vehicle movement in response to steering input.
The next generation GS features new underbody, rear suspension member and front end module components. Increased spot or laser welding has improved rigidity to the door openings, rear under body and rear partition. Additional reinforcement or thicker gauge sheet metal has been employed in the cowl panel, front and rear underbody and rear partition. And the design of the front suspension member, rocker inner and dash panel has been made stronger.
In combination, these enhancements have increased bodyshell torsional rigidity by 14%, allowing the new GS to respond with much greater accuracy to the driver's commands.
The new GS marks the introduction of a completely new approach to the management of airflow over the vehicle body — aerodynamic damping. The basic concept involves bringing the flow of air closer to the vehicle body, using it to help control the vehicle's movement to enhance handling stability.
Allied to smooth, flowing bodywork boasting exceptionally narrow panel gaps and minimal protrusions, the addition of numerous aerodynamic under-body elements and aero-stabilising fins further promotes vehicle stability and helps reduce wind noise to a minimum.
Particular attention has been paid to rectification of the airflow along the vehicle sides to provide body movement damping. The smoothing of airflow in and around the front and rear wheel arches, and the reduction of air pressure within the wheel arch itself contribute to improved steering response, a flat ride and enhanced road holding. In addition, the rear lamp clusters feature aero-stabilising fins which generate a vortex to the rear of the vehicle, helping to improve handling stability.
Acting in combination, these elements give the new GS optimum aerodynamic performance, and a drag coefficient of only Cd 0.26.
The new GS features a double wishbone front and multilink rear suspension system which combines legendary Lexus ride comfort with excellent agility, optimum steering feel and a particular focus on rear stability.
The front, high-mount, double wishbone suspension set-up incorporates newly designed, unequal length upper and lower control arms in forged aluminium, to both reduce system weight and improve ride comfort. The rigidity of upper and lower arms, the hub bearing unit and the steering knuckle has been increased to enhance steering responsiveness. Caster trail has been increased to enhance straight line stability and steering feel.
Optimising roll attitude, the stabiliser arm ratio has been improved, the stabiliser system spring rate increased, and the shock absorber rebound spring rate substantially increased. In addition, lower bushing has been enlarged to minimise the transmission of vibrations.
To the rear, an advanced multilink set-up with toe control bars and an aluminium rear axle carrier has been completely redesigned. The spring and shock absorber have been separated to increase their efficiency and create a more compact design which improves the vehicle's luggage capacity.
Rear stability has been significantly improved through the addition of a rebound spring; increased stabiliser shock absorber arm ratios; the replacement of suspension ball joints with bush joints; the positioning of the toe control arm at the rear and the minimisation of toe change during the suspension stroke.
In addition to greatly increasing rear stability, these components also combine to improve the new GS's roll posture, ride comfort and straight line stability, whilst reducing harshness. Ride comfort has been further improved by the adoption of low-friction oil in both front and rear shock absorbers.
F SPORT Suspension
F SPORT models feature retuned front and rear suspension to further enhance the efficiency of the Adaptive Variable Suspension (AVS) system, maximising body control and steering response for improved vehicle agility.
Both front and rear shock absorber characteristics have been modified to optimise AVS damping control, and the adoption of low-viscosity oil reduces friction for improved shock absorber efficiency. In addition, the rear suspension shock absorber has been inclined further to the rear, and the lower bushing enlarged and stiffened.
In combination, these modifications maximise the AVS system's control of body roll and, hence, improve the vehicle's response to steering inputs for increased agility and a more engaging driving experience.
Featuring 334 x 30mm ventilated discs to the front and 310 x 18mm solid discs to the rear, the GS's braking system has been designed to offer drivers enhanced power and control, with improved pedal feel and a consistently fade-free performance. Simultaneously, tyre friction characteristics and ABS control have also been enhanced to minimise stopping distances.
Brake booster power has been increased, and the pedal shape, angle and ratio changed to provide instant response to changes in applied pedal force and greater controllability. Brake cooling performance has also been improved through an increase in ducted cooling airflow volume, minimising brake fade even under protracted use.
The GS 450h's Electronically Controlled Braking (ECB) system characteristics have also been modified to provide greater responsiveness from the first touch of the pedal.
All GS models fitted with the F SPORT package are equipped with larger, 356 x 30mm ventilated front discs. A world-first, the hat section of the two piece rotor has been fabricated in aluminium to both reduce weight and suppress heat deformation.
Adaptive Variable Suspension (AVS) system
The Adaptive Variable Suspension (AVS) system allows the driver to fine tune the GS's ride characteristics with a choice of two damper settings; 'Normal' mode, for everyday driving comfort, and 'Sport S+' mode, for improved body control and precise responses to steering input whilst cornering.
In response to driving operation, vehicle body motion and road surface conditions, AVS automatically adjusts the performance of the suspension at all four wheels independently activates the adjustable damping force shock absorbers to fulfil a wide range of specific control functions.
Selecting the AVS system's 'Sport S+' mode automatically increases the difference between inner and outer shock absorber damping through corners to further reduce vehicle roll. Simultaneously, VGRS automatically reduces the steering gear ratio by approximately 10% whilst the Electric Power Steering (EPS) increases steering assist torque by some 4%. These measures combine to minimise body roll, sharpen vehicle handling and optimise steering feel for the ultimate in sports sedan driving.
Drive Mode Select System
The next generation GS features a Drive Mode Select function that allows the driver to choose between ECO, NORMAL, SPORT S and SPORT S+ driving modes, maximising either the vehicle's environmental efficiency or its dynamic abilities.
In ECO Drive Mode, engine power output, throttle opening and air conditioning are controlled automatically to maximise fuel economy. In addition to moderate drive force changes, the air conditioning functions are also adjusted, limiting ventilation losses. At temperatures below 10°C (for GS 450h) and 3°C (for petrol version) the seat heater switches on automatically. The air-conditioning changes to recirculation as from 20°C and the airflow volume is lowered when in 'high'. Additionally, the air-conditioning stays switched off until engine cooler water reaches 30.5°C.
The ECO mode can be selected by turning the dial anti-clockwise. Once selected, the meters and the 'ECO mode' indicator are illuminated blue.
In SPORT S mode the powertrain is adapted to increase acceleration response. In the petrol version this results from a shift timing change; in the hybrid version it is achieved through drive force and engine responsiveness enhancements in the partial and full throttle range respectively. SPORT S mode can be selected by turning the dial once clockwise. When selected the meter illumination turns red and the SPORT S mode is indicated on the 12.3'' screen.
Available on GS models equipped with the Adaptive Variable Suspension (AVS), SPORT S+ mode combines the SPORT S mode's enhanced powertrain output with coordinated control of the Vehicle's Dynamic Integrated Management (Step 5 VDIM) including Adaptive Variable Suspension (AVS) and Electric Power Steering (EPS). When equipped with Lexus Dynamic Handling (LDH), also Variable Gear Ratio Steering (VGRS) and Dynamic Rear Steering (DRS) are included.
All these enhance the new GS' stability and steering rewarding the driver with the ultimate in sporting driving dynamics. The SPORT S+ mode can be selected by turning the dial twice clockwise illuminating the meters red and the SPORT S+ mode is indicated on the 12.3'' screen.
In addition, a new Sport-D Control system, activated when SPORT S and SPORT S+ modes are engaged, enhances the performance of the GS 350AWD's automatic transmission. With the gear shift level in D-range, Sport-D Control automatically shifts down the appropriate gear when the vehicle approaches a corner and maintains the gear when cornering, making maximum acceleration available to the driver as he exits the bend.
When M-range is selected, the driver benefits from the total control of fully manual gear changes via steering wheel mounted shift paddles. With rapid up shifting and throttle blipping on down shifts, customers can enjoy the most direct, sporting driving experience the new GS has to offer.
Enhancing the enjoyment of the new GS's expanded breadth of driving style preferences, the ambient illumination of the driver's instruments changes to a tranquil blue in ECO mode, whilst switching to red in both SPORT S and SPORT S+ modes. Switching to SPORT S and SPORT S+ modes in the GS 450h automatically changes the system power indicator into a tachometer.
The Lexus Dynamic Handling (LDH) System
The GS 450h F SPORT can be equipped with the Lexus Dynamic Handling system, making it the world's first hybrid vehicle to feature an integrated four-wheel steering system.
The leading edge platform technology of the Lexus Dynamic Handling system offers an integration of Dynamic Rear Steering (DRS), Variable Gear Ratio Steering (VGRS) and Electric Power Steering (EPS), to coordinate every aspect of front and rear wheel control and provide agile, sharp and confident driving behaviour with a more direct response to the driver's actions.
Monitoring vehicle speed, steering direction and driver inputs, LDH calculates the optimum angle for all four wheels. Using VGRS to the front and DRS to the rear, the system can independently control both front and rear wheel steering angles to greatly improve turn-in response, rear grip, vehicle stability and overall agility when cornering.
The LDH system monitors vehicle speed and yaw rate, steering angle and speed, and lateral G to calculate the required rear wheel steering input, to a maximum of 2.0 degrees. At most speeds below 80km/h the front and rear wheels turn in opposite directions. In certain conditions at speeds over 80km/h, front and rear wheels turn in the same direction.
Further coordinating DRS with VGRS and EPS, the Lexus Dynamic Handling system will automatically customise the adaptive suspension tuning and active safety systems to suit road conditions, vehicle speed and driving style, giving customers the confidence to fully exploit the new GS's exceptional driving performance.