Volkswagen has long touted “German engineering” as the key difference between its cars and their competitors. We’ve echoed the phrase when describing the attributes that have repeatedly put VW Group products on our lists of the 10Best Cars and 10Best Trucks and SUVs; for 2017, that would include the VW Golf/GTI (above), the Porsche 718 Boxster/Cayman and Macan, and the Audi Q7. But does this expression mean anything more than a demographic descriptor of who did the work, or where? To find out, we cornered Stefan Gies, head of chassis development at VW, during a recent test drive in South Africa.
As it turns out, Gies is a passionate spokesman for this subject after 14 years of chassis development work at Audi and VW.
“From my perspective,” he said, “German engineering stands for precision in all that we do—precision in the design and what you feel in the car. Everything the driver touches and controls must instill this feeling of confidence and precision. We want that person to feel that they have the car under control and that it will do exactly what they desire it to do.”
Gies cited body structure as the starting point for what he called “crucial personality traits.” A loose structure shakes, leaving the impression of less robust design. “What’s important is what we call global stiffness—the body structure as a whole—and also local stiffness. By this, we mean that those specific points where the suspension attaches to the body structure must be stiff for the suspension to perform as intended.”
“Everything the driver touches and controls must instill this feeling of confidence and precision.”
— Stefan Gies, Volkswagen Group
Then, he said, suspension architecture comes into play. “By this I mean the geometry of how the wheels move in relationship to the body and how each suspension bushing is designed and tuned to perform in specific ways. Our goal is to separate the various functions whenever possible.” For instance, each axle needs longitudinal compliance—a measure of give—so the wheels move back in a controlled way when the car encounters a bump in the road, softening the impact.
“The bushing that is mainly responsible for resisting longitudinal suspension forces needs to be soft, versus those bushings that handle side forces. When you steer into a corner, we want the suspension to react in such a way that the car doesn’t roll excessively. We tune the car’s response to reinforce the feeling of confidence and precision. Of course some compromise is necessary, but our job is to do an excellent job of balancing the longitudinal and lateral suspension behavior.”
After that, Gies said, “Proper brake-pedal feel and response are other important areas of endeavor for VW chassis engineers. We want the initial pedal travel to be relatively short, but not so short that customers used to different characteristics are confused. During the beginning pedal motion, all the slack in the braking system—the linkage, the brake booster, the pads moving in contact with the rotors—must be taken up. Then, when the force begins to build, we want the pedal to feel very stiff to instill the confidence that the car will stop as quickly as the driver desires.”
Similarly, steering needs a little compliance and then a sense of control, he said. “We want the steering wheel to have a very clear center point where minor road disturbances don’t yield changes in the car’s directional heading. We strive to minimize that slack and to follow it with a linear reaction as the driver begins to turn the wheel off-center,” said Gies. “Picking the right steering ratio and sensitivity are both important. We want the car to be easy to manage while driving dead straight ahead and then very direct in its response so that it feels agile during passing maneuvers.”
He said variable steering ratios are best for cars with sporty driving characteristics, while VW prefers fixed ratios for more mainstream models.
“A few years ago, with the transition from hydraulic to electric power assist, we were not content with the support we received from our suppliers,” Gies noted. “This prompted us to develop our own control algorithms and 20 to 30 software modules to provide the performance characteristics—such as active steering return and resistance to side winds—we sought.”
In its segment, Gies said, the Golf was the first to offer electrically assisted power steering. “We began early and learned a lot from that application. It takes this experience to instill the feeling of confidence and proper feedback from the road in the steering. The fact that we manufacture most of our power-steering gears at our Braunschweig components factory [in Brunswick, about 20 miles from VW Group headquarters in Wolfsburg] also helps us achieve our developmental goals.”
The VW Group has four different types of power-assisted steering, used for various powertrain configurations. Small cars have the assist motor mounted inside the car, attached directly to the steering column. Audi uses a concentric arrangement that works well with its north-south engine orientation. There are also double-pinion and belt-drive configurations to connect the motor to the steering rack itself.
“A significant challenge is translating the motor’s rotary motion to the rack’s axial motion through a recirculating-ball-screw mechanism,” Gies said. “The problem is minimizing the amount of lash and friction with very careful quality control of tolerances.”
So, in essence, German engineering isn’t one thing, it’s everything related to car design and development. Volkswagen experts like Gies take their tasks—and opportunities—seriously. Let’s hope competitors are paying attention and are able to learn from this wisdom.