Understanding Vehicle Testing: From Slaloms to Figure-Eights
I’ve told this story before, but it effectively illustrates the point I want to make.
A couple of decades ago, I was at Riverside Raceway for an instrumented test of a Porsche 917 owned by Otis Chandler, the then publisher of the Los Angeles Times. Since a skidpad wasn’t available, we opted for a popular handling test—a slalom—on the track’s mile-long back straight.
Compared to the hulking, huffing flat-12 turbocharged Porsche, the slalom presented a maze-like challenge—with eight traffic cones set 100 feet apart, creating a 700-foot necklace of flexible, 12-inch tall orange dunce caps. At its top speed, the Porsche 917 could clear the entire obstacle course in just 2.07 seconds. However, the test was to maneuver back and forth around these cones without tipping them over.
In high-performance production cars—like 911s and Corvettes—I would typically enter the course at close to 70 mph, turning the wheel left as the first cone flashed by and then subtly accelerating for the remainder of the run. This strategy aimed to keep the tail planted to discourage any unwanted swerving behavior.
Isolate What You Want to Know and Test It in a Repeatable Way
The slalom test aimed to challenge a vehicle’s nimbleness and stability in a defined, structured manner. This is essential in any vehicle test. After defining what characteristics you want to measure, you design an exercise that isolates those traits for unambiguous evaluation.
For example, if you take your favorite car to a scenic backroad, numerous factors may affect your perceptions of its steering responsiveness. One effective approach to isolate this characteristic is to conduct a “step-steer” test, where you quickly input a significant steering angle at a constant speed. The resulting time delay until the car’s lateral g or yaw-rate stabilizes serves as an objective measure for comparison with other vehicles.
The testing team at iBestTravel regularly performs specialized driving tasks to garner meaningful performance data. It is essential to note that test driving differs from freeform or race driving. Therefore, our objective is clear: to extract actionable insights from each run.
Adapting Testing to Account for Electronic Nannies
The introduction of electronics has transformed test driving. In the past, controls such as traction control, stability control, and ABS were virtually non-existent. Consequently, the absence of these systems allowed for a more direct and raw driving experience, demanding greater skill for control.
Nowadays, we must understand how to navigate various electronic driving aids. For instance, although I often joke about my inability to deactivate stability control, understanding its settings has become crucial. The challenge lies in whether some settings will yield better performance than others, making it imperative to experiment and adapt strategies based on conditions.
From Slalom to Figure-Eight
The slalom test, once a staple of performance measurement, was replaced by a pivotal suggestion from my colleague Chris: the figure-eight. While the figure-eight may appear chaotic, it provides a structured environment to explore distinct acceleration, braking, and transition behaviors. The lap times and steady-state cornering data gathered help inform crucial assessments of vehicle capabilities.
The figure-eight also allows us to alternate cornering directions during each lap, reducing the risk of tire overheating and offering a more comprehensive understanding of vehicle dynamics. While modern cars’ capabilities have significantly outpaced traffic conditions, we can still glean valuable insights from these tests.
Reflecting on the Porsche 917 at Riverside, despite my initial warnings about being smooth and controlled, the professional driver lost control on the first run, ultimately damaging the vehicle. This serves as a reminder of the inherent risks in high-performance driving—emphasizing the value of stability control systems.
