Control Center

The steering wheel of the Porsche LMP1 race car, the 919 Hybrid, is much more than a mere instrument for changing directions. It is the computer with which the drivers control the car’s extremely complex functions.

1 Add boost for passing: This button uncorks the full potential of the drive concept. The magic word is boost. When the driver pushes the red button at the top left of the steering wheel, he calls up the electric energy that the Porsche 919 Hybrid has stored up in its liquid-cooled lithium-ion batteries. At his disposal is a fearsome several hundred horsepower, which suddenly kicks in, pressing him into the seat and converting the prototype into an all-wheeler. The boost can be applied in doses to overtake a competitor, pull away from dense traffic, or add power at the end of a lap for maximum speed on a straightaway. Saving it up for the next lap is not allowed by the rules. Exactly how many horsepower pump into the front axle at the push of a button is top secret. The electric power is a joint recycling product generated from converted braking energy from the front axle and the energy from the hot exhaust flow from the two-liter, four-cylinder turbo engine that powers the rear axle.

2 Brake balance preselection: Switch 2 is the function for rough calculations; buttons BR- and BR+ are the ones for fine-tuning the brake force distribution between the front and rear axles. The default position is a fifty-fifty distribution of the brake force between front and rear. The suitability of this configuration depends on the track, weather, current fuel tank content, and the state of the tires. For example, when a front wheel blocks when braking into a corner, this unambiguous signal indicates that it’s time to shift brake force further to the rear. Marc Lieb says, “I always shift the brake force as far as possible to the rear until the rear axle gets uncomfortably nervous, and then I take it one notch toward the front. In my opinion, that’s the ideal state for optimal deceleration and good steering behavior.” The drivers even change the brake force distribution on a corner-by-corner basis. The rule of thumb: If a strong braking maneuver from a high speed is imminent, shifting somewhat more brake force to the rear axle is advisable.

3 Increase rear traction control: If the rear wheels spin and the rear end slides out when you hit the gas, it’s a clear-cut case for button number 3. TR+ stands for “traction control rear.” The button triggers earlier activation of the electronic system and greater retraction of the engine power working on the rear axle. If the traction control kicks in too early or too intensely for the driver’s taste, he can use the minus buttons on the top left of the steering wheel—likewise specific to the front and rear axles—to dial it back. The task of the electronic driving assistance is optimal driving stability for the best lap times combined with minimal tire wear. The more worn the tires, the more frequently the TR+ and TF+ (F for front) buttons are pressed by the driver. This option somewhat counteracts the decreasing grip level of the tires; in so doing, it stabilizes the driving behavior for a time. Exactly what constitutes optimal driving behavior differs a bit from driver to driver. It is customization at the push of a button.

4 Cruise control for the pit lane: The pit lane in the FIA World Endurance Championship is a dangerous place. The duration of the stops is decisive, and the pressure on the mechanics is accordingly huge. The cars are searingly hot, and fuel is flowing. To reduce the risk somewhat, the pit lane speed limit is 60 km/h. If you drive faster, the penalty is an expensive fine. If you drive any slower, you lose time. To avoid both, the speed is electronically controlled. The driver presses the button on the right side of the steering wheel as close as possible to the line that signifies the start of the pit lane. With his mind already on the driver change, and his fingers in gloves, he still has to be careful not to hit any of the surrounding buttons. Once activated, the cruise control function remains active until it is manually switched off. The engine doesn’t have to be running—the function remains active during the stop. At the end of the pit lane, the new driver presses the button again and hits the track full bore.

5 Hybrid strategy selector: The rotary switch labeled “Strat” sets the energy management for operation of the combustion engine. That makes it practically the big brother of the Boost button, which calls up the electric power. The strategic goal is to make maximum use of the permitted energy limit, but not to exceed it. The amount of energy that can be applied is prescribed: the Porsche 919 Hybrid can apply a maximum of 6 megajoules of electric energy from its two energy recuperation systems on a 13.6-kilometer lap at Le Mans. The energy generated with the gasoline is 139.5 megajoules, which corresponds to 4.8 liters of gas per lap. The amount of energy throughput is determined by various factors. On a wet track, the driver is scarcely able to use up all of the available energy on each lap. If he’s in a tight contest with a competitor, by contrast, his strategy must ensure that he has access to maximum power to attack.