At its present 570 hp, the direct-injected V8 has a specific output of 123.9 hp, which nearly matches the 997 GT3 RS 4.0’s stellar 125 hp/liter and clearly exceeds the 5.7-liter Carrera GT’s 107 hp/liter. The Spyder engine weighs just 290 pounds, can pass all Porsche road-car durability tests, and shares no parts with the RS Spyder V8.
That last point is understandable due to a rather significant difference: The 918 Spyder’s exhaust ports are located topside, inside the cylinder V. Short exhaust pipes exit the engine cover, an attribute Porsche says is unique among production vehicles. There are benefits to the setup beyond the singed trouser legs promised by the 918 Spyder concept’s side pipes. The so-called “top pipes” evacuate hot exhaust gases in the shortest route possible, with less back-pressure. Meanwhile, the intake ports are located low, keeping the engine bay cooler to the benefit of the Spyder’s liquid-cooled lithium-ion battery.
The battery, which provides optimum performance at temperatures between 68° and 104° F, is mounted between the seats and the V8. Its 312 cells have a total energy content of 6.8 kilowatt hours, and can be charged at home via the socket on the passenger-side B pillar. Using a supplied cable standardized for the country of purchase, Porsche says the 918 can be charged within four hours. The cars will also come with a “quick charger,” which can be hard-wired into the owner’s garage and will charge the battery in approximately two hours. The 918’s electric-only range is currently 15 miles depending on how it is driven. Of course, that’s up to the driver, who can select from five modes that sap resources with increasing abandon (see sidebar).
The 918 can also charge its battery on the move through a regenerative braking system considerably more efficient than the systems in the Cayenne Hybrid and Panamera S Hybrid. The latter recover braking energy up to deceleration of 0.15 g, which Porsche says corresponds to about 3.3 pounds of pedal force. The 918 can recover energy at up to 0.5 g, or about 24.3 pounds of pedal force. As in Porsche’s existing hybrids, the 918’s conventional disc-brake system handles harder stops.
The battery sends power to two electric motors, either individually or in parallel. A 107-hp motor drives the front wheels through a fixed ratio, while a 121-hp motor mounted behind the driver sends power to the rear wheels. The forward motor can propel the Spyder up to 15 mph. It functions as needed after that, adding torque to either front wheel until it is disengaged at speeds exceeding 145 mph to prevent over-revving. The rear wheels can be driven by the V8 or the electric motor, or both. Because the rear electric motor sends its power through the seven-speed PDK gearbox, it can contribute all the way up to the 918’s projected 202-mph top speed.
The main powertrain is mounted in a carbon-fiber-reinforced plastic carrier that bolts to the monocoque chassis, which is also rendered in CFRP. Drivetrain components and anything else weighing more than 110 pounds are located as low and as centrally as possible. To lower the V8, the PDK transmission is “upside down,” 935 style. The ’box is based on the unit found in the 997 Turbo, but gets a new case and internals. Weight distribution is said to be 43/57, with a rear bias similar to Porsche’s recent mid-engined cars.
Suspension consists of double wishbones up front and multi-link at the rear. The Spyder’s PASM electronically variable dampers and PCCB ceramic-composite brakes are nothing new on a Porsche, but active rear-wheel steering is. The latter is speed-sensitive and can add a few degrees of lock in either direction. The rear wheels counter the direction of the front wheels to add agility at low speeds but mimic them at high speeds to add stability.
The list of technology will be long, from a reconfigurable thin film transistor LCD dashboard to active aerodynamics that optimize cooling and downforce while minimizing drag. After all, buyers in this realm expect more than mere performance.
Speaking of buyers, the sales plan is as bold as the production date. Porsche has announced a U.S. base price of $845,000. That’s considerably more than the $440,000 Carrera GT — a car that struggled to find 1,270 buyers worldwide after falling short of an initial production cap of 1,500 units. Will Porsche have the last laugh with its 918 Spyder hybrid? We’ll know more in another year and a half.