Modern cars are better than old cars in every way. As much as we love old cars for their looks and their quaintly primitive driving dynamics, it’s just a fact that they can’t keep up with a new car. Automakers have invested hundreds of billions of dollars in research and development to produce a modern car that is both faster and safer than anything we had even 20 years ago.
Digital Trends wanted to explore exactly how the mechanical and electronic tech in a modern car delivers high performance. We also wondered how new tech helps make up for any, shall we say, deficiencies in the driver’s skill. To get some answers, we headed for Palm Springs, California and the BMW Performance Center West located at The Thermal Club raceway.
For the last four years, the BMW Performance Center West has been located adjacent to the Thermal tracks, and maintains a partnership with the facility. BMW has a maze-like set of roads that can be configured into a variety of tight autocross-style courses, a state-of-the-art skidpad with sprinklers, and access to the Thermal facility for a full road course experience. The Performance Center West in Thermal and East in Greenville-Spartanburg, South Carolina offers a variety of hands-on classes ranging from two-hour performance experiences to multi-day performance driving courses. Classes include options in MINI vehicles and BMW motorcycles as well as BMW cars and SUVs.
The BMW buffet
To experience the full range of options, we took a two-hour experience followed by road course time and a skidpad exercise. The two-hour class includes short-course time in a BMW M2, M4, M840i, and the X5M and X6M SUVs. For the record, the cars we were driving were unmodified in any way. They were the same cars you can get at any BMW dealer, running on stock Continental summer tires.
After a rotation through all the vehicles to get the feel for how size and weight affect handling, students tried their skills with timed runs in identical M4 sedans. The timed run course includes challenges like a “stop box” designed to stress threshold braking and a variety of corners and slaloms.
Running the various BMWs through their paces was a keen lesson in how advanced technology supports the driver at the limit of traction. Most drivers only rarely trigger their car’s stability controls, and then only for a moment. In normal daily driving, it just doesn’t happen that much. By driving the cars under extreme conditions, the systems were triggered on every lap. Learning to work with the automation is key to getting a good lap time.
Layers of control
BMW vehicles (and pretty much every other brand) come with a Dynamic Stability Control (DSC) system that uses an integrated system of sensors and control units to maintain and maximize traction and driver control. If any tire begins to lose grip, the system can route engine power or apply braking force to regain traction.
BMW vehicles allow for the DSC system to be partially turned off or fully deactivated. The partial deactivation leaves the traction control active to get the car moving in slippery conditions or to allow full acceleration out of corners on dry pavement. High-performance M models also offer an additional mode called M Dynamic Mode (MDM), which allows for additional wheel slip and later intervention of the stability and traction control systems.
The DSC system is the core of the tech that keeps any car pointed in the right direction when the driver screws up, but it’s not the only tech working for you. The DSC is layered with other systems that monitor specific events and functions. Those systems include:
- Automatic Stability Control to modulate engine torque for traction. This system prevents wheel spin under hard acceleration.
- Dynamic Traction Control automatically reduces stability control intervention when the car is on a loose surface like gravel.
- Performance Control adjusts engine power and braking forces applied to each wheel to reduce understeer during cornering.
- Electronic Brake Force Distribution regulates the braking forces between front and rear axles to stabilize the vehicle under hard braking. This keeps the rear end from coming around under threshold straight-line braking.
- Corner Brake Control regulates brake pressure under braking while cornering to help stabilize the vehicle and prevent spins.
- Dynamic Brake Control helps the driver apply maximum brake pressure under panic braking to shorten stopping distance.
How you know it’s working
As we mentioned, part of the purpose of a test course like the Performance Center is to allow the driver to trigger the systems over and over again, to get used to the feeling.
With the systems fully engaged, drivers experience sensations like the brake pedal pulsing under hard braking, or a kind of momentary “grinding” sensation as the brake controls modulate braking force to prevent the wheels from locking up in a hard braking situation. Drivers may also feel the systems intervening through the steering wheel as the vehicle applies braking action to individual wheels to help navigate around a corner smoothly. In extreme cases, the car will slow dramatically as the systems work together to send the car where the driver is indicating with his or her steering and throttle inputs.
Of all the vehicles we tested, one was unique. The M850i xDrive is a large luxury car, and BMW equips this model with rear-wheel Integral Active Steering, plus a few related tech features. In low speed turns, the rear wheels turn slightly in the opposite direction of the front wheels to create a smaller turning circle for tight environments such as parking lots or driveways. At higher speeds, the rear wheels steer in the same direction as the front wheels to achieve quicker directional maneuvers such as emergency lane changes.
It takes some time to get used to this feature because you get a little more steering than you expect. In practice, it feels like the rear end is trying to break loose, but it’s not. It’s just turning the rear wheels in a way you haven’t experienced before.
In addition to turning the rear wheels, the system includes Yaw Rate Control to stabilize and counteract a tendency to understeer, and Yaw Moment Compensation to stabilize the car during heavy braking. The M850i is a big car, and on the tight handling course it had a tendency to understeer, mostly due to our tendency to offer more steering than the four-wheel steer system needed. The stability control then had to intervene to save us.
Larger SUVs pose a daunting challenge on the handling course. The curb weight of an X6M is 5,185 pounds, and the X5M is even heavier at 5,260 pounds. The xDrive all-wheel-drive system in these vehicles is designed to help get these larger vehicles to change direction quickly. This requires a stout contradiction, if not outright defiance of the laws of physics.
The BMW M xDrive system normally sends all of the power to the rear wheels to allow for a traditional rear-wheel-drive performance experience. However, when the rear tires have reached their limits of grip, some power is transferred to the front wheels to help pull the vehicle through the corner.
The xDrive system works in concert with the stability and traction controls to vector just the right amount of engine power to each wheel to maximize traction and control. This allows the X5M and X6M to far exceed the performance envelope of a traditional SUV.
Still, don’t get the wrong idea here. Piloting the larger SUVs on a tight handling track at speed is a workout, even with all the traction and stability technology working for you. The tech can improve traction and steering, but it will never make a big SUV handle like an M2 coupe.
Putting it all together
As a final exercise, we took the M4 sedans onto the Thermal south course for a few hot laps. We placed the cars in M Dynamic Mode to allow a little more slip angle in the corners. With the morning’s experience under our belts, it didn’t take long to hit triple digits on Thermal’s long straights. Track driving enthusiasts will find a lot to like in the M4. With M Dynamic Mode, this car will let you drive with much more latitude than most street-legal cars, but the tech is still there to save you from embarrassment and expense if you happen to get a little too enthusiastic.
The takeaway from our day in California was simple: technology has opened high performance driving to a much wider audience than ever before. By expanding the performance envelope while providing assistance to maintain critical safety boundaries, vehicles like the BMW M models give the driver a chance to hone their performance driving skills while minimizing fear of a wreck. That’s a benefit worth having.
Published at Wed, 14 Aug 2019 10:09:33 +0000