2015 Porsche 918 Spyder
Meet the future, no waiting.
You might think that the Porsche 918 Spyder shouldn't be a hybrid; that the car's electric motors and batteries add weight, unnecessarily complicate its powertrain, and corrupt its mechanical purity; that the very point of a car like this is to be anything but green. Those are valid issues, but you could also argue that the true purpose of a supercar is to push boundaries. While a 918 powered solely by its 608-hp, 9150-rpm, flat-crank V8 would be impressive, that car would offer little technological advancement beyond—and a scant three horsepower more than—its predecessor, the 2004–2005 Carrera GT. More than anything, the 918 is the current vision of the automotive future, an $845,000 peek at things to come.
Oh, and let's not forget the power-to-weight ratio, which rivals that of the Bugatti Veyron. And the factory-claimed 0-to-62-mph time of 2.8 seconds.
Those last two figures apply only when the car is motivated by both its electric and gasoline propulsion systems. In our first moments behind the wheel of prototype number 25 at Porsche's Leipzig test track, we're moving thanks only to the 918's two electric motors. The front unit makes 127 hp, while the rear, sandwiched between the engine and the seven-speed dual-clutch gearbox, is good for 154 hp. Combined, the two are more powerful than the first-generation 911 Turbo, though the 918's 3715-pound mass means it needs nearly seven seconds to reach 60 mph on electric power alone. A heavy right foot or accelerating beyond 93 mph will activate the 4.6-liter gasoline engine. But before either of those things happens, we brush the brake pedal to negotiate an exact replica of Monza's Parabolica corner. (Germans are nothing if not thorough with their test tracks.)
The massive disc brakes are made of a carbon-ceramic composite, but in this case, we didn't use them. The 918 is programmed to use its electric hardware to accomplish about a third of overall braking. Whereas most electrified cars use traditional friction brakes for deceleration greater than 0.2 g, the 918 can slow by up to 0.5 g by using its electric motors as generators.
Porsche uses a unique system to convert the pressure from your foot into a combination of regenerative and friction braking: When you hit the pedal, you're activating a hydraulic system similar to that of a conventional car, but the system can bleed a portion of brake pressure into what Porsche calls an "active volume reservoir." One of the 918's countless computers then instructs the motors to make up the decelerative difference. If needed, the car can reintroduce the pressurized, stored fluid back into its braking system via an electromechanical servo.
In the cockpit, this hocus-pocus is only detectable via slightly uneven brake-pedal feel. The car we drove was a preproduction prototype and Porsche is working to iron out the remaining kinks, but the 918 already offers the best brake feel we've experienced in a hybrid.
As with a lot of hybrids, the driver can change how the car manages its power; a red-faced knob on the steering wheel selects different powertrain modes. E means electric-only, in which the 385-volt, liquid-cooled, lithium-ion battery gives a claimed range of up to 18 miles. (The optional 20-kW plug-in charger can fully charge the battery in 25 minutes, so you can tell your Prius-driving neighbors to shove it.) In Hybrid mode and under hard acceleration, the 918's V-8 starts with a bark reminiscent of the RS Spyder Le Mans engine on which it's based—but it falls silent when you lift off the gas. Sport Hybrid mode keeps the engine lit and allows up to 20 seconds of electric boost.
Track time was limited, so we went right to Race Hybrid mode, where the 918's technology is fully exploited. The front radiator flaps stay open for maximum cooling, the rear wing adopts a maximum-downforce angle of attack, and diffuser inlets under the nose open for aerodynamic balance. Flat-out upshifts are executed in less than 50 milliseconds.
All this technology wouldn't be impressive if the car beat you over the head with it. The 918 is arguably the most complex car on earth, yet that complexity is hardly detectable behind the wheel. The steering offers more feedback than the wheel in Porsche's own 911; like most electrically assisted racks, its signal is filtered, but the essential information comes through loud and clear. (Famed Porsche test driver Walter Röhrl was present at the 918 media introduction and gave tail-out rides around the wet track. When someone asked him about the importance of steering feel, he demurred, saying that he didn't care how the wheel felt, only that he knew if the front tires were sliding. Interesting.)
With exhaust pipes exiting skyward inches behind your head, you might mistake the 918 for a Le Mans prototype, if not for its futuristic cabin and multifunction touch screen. As speed increases, you forget about the car's carbon-fiber chassis, which features composite inserts instead of aluminum, something seen only in the most advanced race cars. You don't care that the stainless-steel engine cover has 10,346 laser-drilled holes. You aren't thinking about the fact that the titanium-rod, dry-sump V8 produces 133 hp per liter without the use of a turbocharger. If you remember that the front electric motor is decoupled at speeds over 146 mph, it won't matter. And if someone told you, as you flung the 918 into a corner, that the car's cornering stability is enhanced by individually steered rear wheels—six degrees of range each—you'd probably just ignore them. Because the 918 is amazing no matter how it does its job. And when you're driving it, that's all you care about.
Given that the technology here will soon trickle down to other Porsches, that's important. And while the 918 might seem like a step in the wrong direction to some, at least compared with the lighter and more traditional Carrera GT, it's worth remembering that some people still pine for an air-cooled 911.
Stuttgart didn't make this car to rouse nostalgia. It was built to advance the science of the automobile, and in that sense, it's a success. In the way it makes the hair on the back of your neck stand up, it still does its job. It's still a Porsche.
0 comments:
Post a Comment