By Christopher A. Sawyer
The Virtual Driver

(June 1, 2013) Porsche’s engineering brief for the 918 Spyder was direct, but hardly simple: combine top-level motor racing technology with excellent everyday utility, and maximum performance with minimum consumption. This task required a clean sheet of paper, and has resulted, says Porsche, in a car that will “act as the gene pool for the Porsche sports cars of the future.”

The 918 Spyder is an all-wheel drive plug-in hybrid electric vehicle powered by the combination of a 608 horsepower 4.6-liter V8, and an electric motor at each axle. With its ability to increase traction in corners and provide extra acceleration, this system allowed a prototype 918 to slash nearly 20 seconds off the lap time of its predecessor, the Carrera GT, on the Nurburgring’s North Loop. And though the mark now stands at 7:14, more testing on the North Loop is planned.

The engine is coupled to the hybrid module, comprised of a 115 kW electric motor and a “decoupler” that serves as the connection to the V8 engine. Because it is a parallel hybrid, the 918 Spyder’s rear axle can be powered by the V8 or electric motor individually, or via both jointly. The power unit sits in front of the rear axle, and does not have any direct mechanical connection to the front axle.



A mapping switch on the steering wheel allows the driver to choose from one of five operating modes. They are:

    • E-Power, the default when the battery is sufficiently charged, can cover up to 18 miles on electric power, accelerate from 0 to 62 mph in seven seconds, and reach a top speed of 93 mph. If battery’s charge level drops below a set minimum, the powertrain controller switches to hybrid mode.

    • Hybrid mode maximizes both efficiency and fuel consumption, and can be modified to take into account current driving conditions and performance demands.

    • Sport Hybrid operates the internal combustion engine continuously, and it provides the bulk of the motive force. The electric motors provide extra power as and when needed.

    • Race Hybrid again relies on the combustion engine, and uses it to recharge the battery when it isn’t being used to its maximum. As before, the electric motors provide additional power, and the shift program of the dual-clutch PDK transmission is modified to support performance driving. Battery charging is not constant, it fluctuates over the entire charge range, and the electric motors are run at maximum output for short periods. Porsche claims this strategy makes electric power available for several fast laps.

    • Hot Lap is the final mode, and releases reserves that only can be activated from Race Hybrid mode. It pushes the battery to its maximum, using all of the available energy for a few fast laps.

The 4.6-liter V8 produces 608 horsepower, and is a derivative of the engine found in the RS Spyder. With a rev limit of 9,150 rpm, the 918 Spyder’s engine features titanium connection rods; thin-wall, low-pressure cast crankcase and cylinder heads; a lightweight, high-strength steel crankshaft with 180-degree crankpin offset; thin-wall alloy steel/nickel exhaust system; dry-sump lubrication and a separate oil tank and oil extraction.

Ancillaries like the oil tank and the air filter box are integrated into the subframe, and the induction system is made of carbon fiber. There are no external belt drives, making the motor quite compact. Output per liter is more than 132 hp, the highest of any Porsche naturally aspirated engine. In contrast, the Carrera GT produced 106 hp/liter.

One other thing the 918 Spyder has that the Carrera GT didn’t are tailpipes that end immediately above the engine. A solution often seen in Formula 1, this design reduces exhaust system backpressure and engine compartment heat buildup. This required putting the intake on the outer surface of the block, the exhaust in the valley of the engine, and reduced heat transfer to the lithium-ion battery module.



The seven-speed PDK transmission is mounted upside down — rotated 180 degrees about its longitudinal axis — to lower the car’s center of gravity. When coasting, that is when no power is required on the rear axle, the V8 and electric motor are decoupled by opening the PDK’s clutches and the decoupler mechanism.

The front electric drive unit, on the other hand, is a 95 kW electric motor that drives the front wheels at a fixed ratio. To prevent the motor from overspeeding at high velocities, a second decoupler separates it from the wheels. Drive torque is independently controlled for greater responsiveness.

A liquid-cooled lithium-ion battery consisting of 312 individual cells and an energy content of about seven kilowatt hours provides the electrical energy. It’s warranted for seven years. The charge port is located in the passenger-side B-pillar, and is standardized for the country in which the car is purchased.

Located close to the battery, the charger changes alternating current to direct current with a maximum charge output of 3.6 kW. Porsche will supply a universal AC charger that will allow the 918 Spyder to be charged from a conventional 110-volt wall outlet in seven hours. This charger also can be installed at home in the owner’s garage using a charging dock that enables rapid charging within approximately two hours. In addition, the Porsche Speed Charging Station, a DC unit, is available as an option, and can fully charge the 918 Spyder’s battery pack in 25 minutes.

When trying to get the greatest work out of onboard electricity, weight is the greatest enemy. That’s why the entire load-bearing structure of the 918 Spyder is made from carbon fiber. Separate crash elements front and rear act as sacrificial members, and reduce the amount of energy passed along to passengers and the main structure. To help handling, the drivetrain, as well as all components weighing more than 110 pounds are located as low and as centrally as possible. This places 57% of the car’s 3,715 pound curb weight (3,616 pounds with the “Weissach” package) over the rear axle, and 43% on the front. The center of gravity, claims Porsche, is close to the height of the wheel hubs.

Fitted with multi-link suspension front and rear, the 918 Spyder has adaptive dampers and rear-wheel steering. Electro-mechanical links at each rear wheel can steer the rear wheels up to three degrees in the same (in-phase), or opposite (out-of-phase), direction to the front wheels. This speed-sensitive system uses out-of-phase at lower speeds to reduce the car’s turning circle and sharpen turn-in. At higher speeds, the system steers in-phase with the front wheels to keep the rear stable.

Porsche’s latest also has active aerodynamics that is tuned to the operation of the hybrid drive system. In “Race” mode, the rear spoiler is set at its maximum angle of attack to generate the highest downforce. In addition, the spoiler between the two wing supports extends, and a pair of adjustable flaps in the underfloor in front of the front axle open to direct air to diffuser channels.

Switch to “Sport” mode, and the rear wing’s angle of attack is lowered slightly and the underfloor flaps are closed in order to increase top speed. Choose “E” mode, and the rear wing and spoiler are retracted and the underfloor flaps closed to reduce drag. In “Race” and “Sport” modes, air inlets under the front headlights also are opened to increase the intake of cool air. Dial up “E” or “Hybrid” modes, however, and they are closed once the car starts moving to decrease aerodynamic drag. Should cooling demands increase, or the car exceed 80 mph, and these slots reopen to admit more cool air.

The Weissach Package

Those looking for the ultimate in performance will be able to order tan appropriately priced Weissach Package. Immediately recognizable by its use of colors and designs first seen on Porsche race cars, this package features a roof panel, rear wings, rearview mirror housings and windshield pillar frames fabricated from visible-weave carbon fiber. In addition, Alcantara replaces leather for much of the trim, and the aluminum interior highlights are replaced by more visible-weave carbon fiber. Magnesium wheels reduce unsprung mass by a total of 77 pounds, six-point harnesses replace the standard three-point units, film coating is used instead of paint on the body, and visible-weave carbon fiber aerodynamic pieces are added to the exterior.

The Virtual Driver