McLaren Automotive's new P1 plug-in hybrid supercar, to be unveiled at the 2013 Geneva Motor Show, will be propelled by a "substantially revised" 3.8-L twin-turbo V8 gasoline engine coupled to an electric motor—a powertrain combination generating a claimed 916 PS (903 hp) and 900 N·m (664 lb·ft). Formula One-derived DRS (drag reduction system) and IPAS (instant power assist system) technologies offer an increase in straight-line speed and instant power boost. The V8 is an updated version of the company's M838T unit, with optimized cooling and durability under the higher loads. It generates a claimed 737 PS (727 hp) at 7500 rpm and 720 N·m (531 lb·ft) from 4000 rpm. The unique cylinder block casting incorporates the electric motor. All drive is channelled through the dual-clutch seven-speed gearbox to the rear wheels. In developing the IPAS technology for the P1, engineers prioritized power delivery over energy storage. This is achieved via a lightweight (212 lb/96 kg) battery pack offering what McLaren claims is greater power density than any other automotive battery pack on sale today. The pack's sophisticated thermal management system is flow-balanced, so that each individual cell is cooled to precisely the same temperature, says the company.