Porsche 918 Spyder, a high speed high fuel efficiency supercar for the future
The Porsche 918 Spyder plug-in hybrid supercar is debuting at this years International Motor Show (IAA) in Frankfurt. Porsche claims this super sports car with a plug-in hybrid drive train marks "the beginning of a new era for sports car manufacturing," because it offers "impressive dynamic performance" (0-60 in 2.8 seconds) combined with the "fuel consumption of a compact car." The company is looking to this car to be the "gene pool for the Porsche sports cars of the future."
The phrases "fuel efficient" and "supercar" and "sports car" seem to be incompatible, yes? As emissions regulations tighten, we may be able to have our cake and eat it too, if ones criteria for "car" is "extremely fast," depending on what the automakers do to electrify their sports cars.
Porsche's goal was to create the sports car for the next decade, by using a highly efficient and powerful hybrid drive train. The load bearing structures are all made of carbon fiber reinforced polymer, for its ultra strong and ultra light-weight characteristics.
The all-wheel drive train uses a combination of combustion engine and electric motor for the real axle, and a second electric motor for the front axle. The individually controllable front drive gives new driving strategies for extremely high, safe, cornering speeds. An electric boost mode is available simply by pressing the accelerator pedal down fully.
The steering system includes rear-axle steering. Depending on speed the rear axle can be steered in the same direction as the front wheels, or in opposition to them. This makes cornering even more direct, faster and more precise, as well as reducing the turning circle.
Porsche engineers defined five operating modes on the 918 Spyder PHEV to operate the gas engine and electric motors in different combinations. These modes are settable via a switch on the steering wheel.
E-Power: This is the default operating mode, if the battery pack has enough charge. In this mode the 918 Spyder can go 18 miles in electric mode. Running just on electricity it has a 0-60 time of 7 seconds, and can reach speeds up to 93 miles/hr.
Hybrid: In this mode, electric motors and combustion engine work alternatively looking to maximize efficiency while minimizing fuel consumption. The system automatically switches between electric and combustion components depending on the driving situation.
Sport Hybrid: In this mode the combustion engine runs continuously and provides the main propulsion. The electric motors are used for boost and to help optimize use of the combustion engine.
Race Hybrid: This is meant for maximum performance. The combustion engine is used primarily under high load, and is used to recharge the battery when its demand is lower. The electric motors also provide boosts, running at full power to deliver the best performance for the race track. The system doesn't attempt to ensure battery pack state of charge will remain constant.
Hot Lap This is activated only from Race Hybrid mode, and lets the car run the electric motors at full power. It's meant to give you the fastest possible speeds, if you're content with just a few laps of boost. In this mode the car will consume all the energy in the battery pack.
The 4.6 liter eight cylinder engine produces 608 horsepower, and is derived directly from the engine on the RS Spyder. The electrified side of the equation is a 115 kilowatt electric motor in a parallel hybrid configuration (meaning both the electric motor and gas engine drive the wheels). The transmission allows for either unit to drive the wheels alone, or for them to operate together. The electric motor on the front axle is rated for 95 kilowatts, and drives the front axle through a fixed gear ratio.
The lithium ion battery pack contains about 7 kilowatt-hours of energy. To help it run at full power in performance conditions, the battery pack is liquid cooled with a dedicated cooling circuit. Recharging the battery pack takes 7 hours via a 120 volt normal household outlet, or two hours using a regular level 2 charging station. An optional "Porsche Speed Charging Station" uses a DC Fast Charging system, and a 25 minute recharge time.
In September 2012, a 918 Spyder prototype set the current lap speed record for the North Loop of the Nürburgring at 7:14 minutes. Porsche promises more test drives of that track soon.
Porsche is no newcomer to plug-in hybrids. In fact it was Dr. Ferdinand Porsche, the founder of the company, who invented the plug-in hybrid drive train in the early 1900's.