Porsche 918 Spyder plug-in hybrid: 211mphMay 15, 2013
The 887hp Porsche 918 Spyder plug-in hybrid features a mid-mounted 4.6-litre V8 engine and two electric motors which combine to deliver 0-62mph in 2.8 secs, a 211mph top speed, 85mpg and 79 g/km CO2.
Yes, these figures sound unbelievable, and of course the 85mpg is based on the NEDC test, which bears no relationship to driving at 211mph.
The unique all-wheel drive concept has a combination of combustion engine and electric motor on the rear axle and the second electric motor on the front axle, and is based on knowledge gained by Porsche racing the successful 911 GT3 R Hybrid.
The central and low position of the lithium-ion battery directly behind the driver helps to concentrate masses and lower the centre of gravity.
When the vehicle is started up, ‘E-Power’ is the default operating mode as long as the battery is sufficiently charged. In ideal conditions, the 918 Spyder can cover over 18 miles (30 km) on purely electric power. Even in pure electric mode, the 918 Spyder accelerates from 0 – 62 mph in less than seven seconds and can reach speeds of up to 93 mph. In this mode, the combustion engine is only used when needed. If the battery’s charge state drops below a set minimum value, the vehicle automatically switches to hybrid mode.
In ‘Hybrid’ mode, the electric motors and combustion engine work alternately with a focus on maximum efficiency and minimum fuel consumption. The use of individual drive components is modified as a function of the current driving situation and the desired performance. The Hybrid mode is typically used for a fuel economy-oriented driving style.
In more dynamic situations, the 918 Spyder selects the “Sport Hybrid” mode for its power sources. The combustion engine now operates continuously and provides the main propulsive force. In addition, the electric motors provide support in the form of electric boosting or when the operating point of the combustion engine can be optimised for greater efficiency. The focus of this mode is on performance and a sporty driving style at top speed.
‘Race Hybrid’ is the mode for maximum performance and an especially sporty driving style. The combustion engine is chiefly used under high load, and charges the battery when the driver is not utilising its maximum output. Again, the electric motors provide additional support in the form of boosting. Furthermore, the gear-shifting programme of the PDK is set up for even sportier driving. The electric motors are used up to the maximum power output limit to deliver the best possible performance for the race track. In this mode, the battery charge state is not kept constant, but instead fluctuates over the entire charge range.
In contrast to ‘Sport Hybrid’ mode, the electric motors run at their maximum power output limit for a short time for better boosting. This increased output is balanced by the combustion engine charging the battery more intensively. Electric power is thus available even with several very fast laps.
The ‘Hot Lap’ button in the middle of the map switch releases the final reserves of the 918 Spyder and can only be activated in ‘Race Hybrid’ mode. Similar to a qualification mode, this pushes the traction battery to its maximum power output limits for a few fast laps. This mode uses all of the available energy in the battery.
The main source of propulsion is the 4.6-litre, eight cylinder engine that produces 612 hp of power. The V8 no longer supports any auxiliary systems, there are no external belt drives and the engine is therefore particularly compact. Weight and performance optimisations achieve a power output per litre of approx. 132 hp/l – the highest power output per litre of a Porsche naturally aspirated engine – which is significantly higher than that of the Carrera GT (106 hp/l) and outstanding for a naturally aspirated engine.
The V8 engine is coupled to the hybrid module, since the 918 Spyder is designed as a parallel hybrid: exactly like the current hybrid production models from Porsche. Essentially, the hybrid module comprises a 115 kW electric motor and a decoupler that serves as the connection with the combustion engine. Because of its parallel hybrid configuration, the 918 Spyder can be powered at the rear axle either individually by the combustion engine or electric motor, or via both drives combined. As is typical for a Porsche super sports car, the power pack in the 918 Spyder has been placed in front of the rear axle, and does not have any direct mechanical connection to the front axle.
On the front axle, there is another independent electric motor with an output of approximately 95 kW. The front electric drive unit drives the wheels at a fixed ratio. A decoupler de-couples the electric motor at high speeds to prevent the motor from over-revving. Drive torque is independently controlled for each axle.
The electric energy for the electric motors is stored by a liquid-cooled lithium-ion battery comprising 312 individual cells with an energy content of about seven kilowatt hours. The battery of the 918 Spyder has a performance-oriented design in terms of both power charging and output, so that it can fulfil the performance requirements of the electric motor. The power capacity and the operating life of the lithium-ion traction battery depend on several factors, including thermal conditions. That is why the battery of the 918 Spyder is liquid-cooled by a dedicated cooling circuit. The global warranty period for the traction battery is seven years.
To supply it with energy, Porsche developed a new system with a plug-in vehicle charge port and improved recuperation potential. This vehicle charge port in the B-column on the front passenger side lets users connect the storage battery to a mains supply at home and charge it. The charge port is standardised for the country of purchase. The on-board charger is located close to the traction battery. It converts the alternating current of the mains supply into direct current with a maximum charge output of 3.6 kW.
Using the supplied Porsche Universal Charger (AC), the traction battery can be charged within four hours from a ten ampere rated, fused power socket on the German 230 Volt mains supply, for example. Furthermore, the Porsche Universal Charger (AC) can be installed at home in the garage using the Charging Dock. It enables rapid and convenient charging within approximately two hours, irrespective of regional conditions. The Porsche Speed Charging Station (DC) is available as an optional extra. It can fully charge the high-voltage battery of the 918 Spyder in just 25 minutes.