Chassis development of the next-gen Golf GTI
Volkswagen Group has released details of its eighth-generation Golf GTI development, which they say takes the practical hot hatch formula to the next level. Volkswagen engineers focused on improving stability, precision and cornering grip for better driving dynamics while maintaining the everyday comfort of the GTI.
“The Golf GTI has always been synonymous with pure driving dynamics,” says Karsten Schebsdat, Volkswagen’s Head of Driving Dynamics, Steering and Control Systems. “Few other vehicles in this category offer a similarly finely tuned balance between sportiness and comfort. Thanks to the combination of new running gear setup plus torque-sensing limited-slip differential (VAQ) and Vehicle Dynamics Manager we were able to elevate the outstanding overall performance of the GTI to an even higher level.”
The running gear setup on the new GTI features several modifications designed to increase precision and driving stability. The strut-type front suspension has reconfigured wishbone bearings and revised damping hydraulics. In addition, the springs and buffer stops are reconfigured to give a front axle spring rate five percent higher than Mk7 GTI. The eighth-gen car also features a new lightweight aluminium subframe. The multilink rear axle features similar modifications, including a new wheel mount, wishbone bearing and spring setup, and reconfigured auxiliary springs. As a result, the spring rate at the rear axle increases by 15 percent compared with the Mk7. In addition, the damping bearings are new, as are the damping hydraulics.
Volkswagen’s Vehicle Dynamics Manager—a new driving dynamics control system—debuted on the Golf Mk 8. It closely integrates the electronic stability control (ESC) with the electronic differential locks (XDS®) and the optional DCC® adaptive damping system. Moreover, adapting the individual wheel damping 200 times a second can deliver particularly agile and accurate handling.
The new GTI now comes standard with an electronically controlled torque-sensing limited-slip differential. Compared with fully mechanically operated differentials, the system in the GTI offers a variable degree of intervention depending on the actual driving situation and ESC, EDS and XDS+ functions. This makes it possible to avoid steering corruption, as is the case with mechanical differentials. Thanks to a multi-plate clutch, the VAQ differential optimizes grip and handling in fast corners, thus enhancing the performance and helping to decrease understeer, a traditional weakness of front-drive cars. The GTI can handle corners in a neutral stance and also accelerates without any loss of traction. This is due in part to the fact that the locking torque of the VAQ differential can be significantly increased in Sport mode. On the racetrack, it is possible to adapt the ESC intervention in two stages. In ESC Sport mode, the ESC thresholds and ASR slip thresholds are increased to reduce the intensity of interventions. In ESC Off mode, ambitious drivers can deactivate ESC altogether.
Available adaptive chassis control (DCC) continuously reacts to the road surface and driving situation. For the first time, the DCC running gear’s lateral dynamic components in the new GTI are coordinated and then further optimized by the Vehicle Dynamics Manager. Via the Driving Mode Selection settings, the driver can influence the reduction in body motion as desired. In addition, the required damping is calculated for each wheel and adjusted at the four dampers within fractions of a second. This ensures that DCC can provide the highest level of driving comfort and ideal driving dynamics in conjunction with the Vehicle Dynamics Manager.
In the latest DCC generation, the vehicle setup can be extended in Individual mode to go beyond the existing range of the fixed Comfort, Eco and Sport modes. The driver can accurately set and store their personal driving profile using a digital slider. Beyond the Comfort setting, the body is “decoupled” from the road surface as much as possible, thus boosting driving comfort. Beyond Sport mode, there is an extended setting range with maximum damping for minimized body movements and extremely direct and neutral vehicle handling.
Enhanced “progressive” steering is standard on the new GTI. The engineers set up the steering ratio more directly than a standard linear steering gear while applying new software algorithms and a new software application. While conventional steering systems operate on the basis of a fixed gear ratio, the steering in the GTI applies a progressive gear ratio. This significantly reduces the amount of lock required to steer when manoeuvring and parking. On winding country roads and when turning off, the driver will notice sharper responses thanks to the more direct setup. It also means that the driver does not have to change their hand position as frequently.
Lock to lock, there are just 2.1 turns in the new GTI with 18-inch wheels and tires. In terms of technology, progressive steering is differentiated from the basic steering system by variable steering rack and pinion gearing as well as a more powerful electric motor. In contrast to systems with fixed steering ratio, which are always forced to compromise between driving dynamics and comfort, the gearing of the steering rack is considerably modified functionally using the steering stroke. As a result: the transition between indirect steering straight-ahead response and direct response to larger turning angles is more agile.