Porsche continues to introduce new 911 variants for 2015, the latest of which are the Targa 4 and Targa 4S. The current 911 is based on the updated 991 platform that debuted with the Carrera and Carrera S in 2012. Several engines are available for 2015. In the Carrera, Carrera 4 and Targa 4, buyers get a 3.4L horizontally-opposed direct-injected 6-cylinder that makes 350 horsepower. Carrera S, Carrera 4S and Targa 4S buyers get a slightly larger 3.8L flat-6, which makes 400 horsepower. The 50th Anniversary Edition, the GT3, the Turbo and the Turbo S all use different versions of this same 3.8L engine, making different power in each variant. In the 50th Anniversary Edition, the engine makes 430 horsepower, while in the GT3 it makes 475 horsepower. The addition of two turbochargers brings horsepower up to 520 and 560 for the Turbo and Turbo S, respectively. All engines are mated to a standard 7-speed manual transmission. The 7-speed PDK double-clutch automatic is optional, and standard on the Turbo S. In the manual, the ratios are close together in every gear except 7th, which helps to achieve a better fuel consumption rate during highway use. Other features include electric power steering and a hydraulic decoupler of the front and rear sway bars, known as Porsche Dynamic Chassis Control. In addition, 911s feature a rear-wheel torque vectoring system that helps build traction using the rear brakes in conjunction with the rear differential. Inside, the 911 interior features styling touches consistent with Porsche's Panamera and Cayenne. There's no mistaking the design as anything other than 911, however, with a host of gauges flanking a large tachometer, mounted front and center. The center console sports a large color touchscreen monitor for navigation and stereo functions. Overall, the 911 strikes a good balance between being a focused sports car and a luxurious cruiser, never feeling too hardcore to keep its occupants comfortable. Several packages add features such as special sports seating, Bose audio, ambient lighting, auto dimming mirrors and more. The Sport Chrono Package includes dynamic engine mounts, a dash-mounted analog and digital stopwatch, performance display, a Sport Plus button to control engine mapping and throttle response and launch control for cars equipped with PDK.