Porsche flat-six engine

The Porsche flat-six engine series is a line of mechanically similar flat-six boxer engines, produced by Porsche for over 60 consecutive years, since introduced in the 1963^[8][9] rear-engine Porsche 911, and as mid-rear mounted racing engine in the 1966 Porsche 906 Carrera 6, each with 2000cc.

All Porsche F6 boxer engines, naturally aspirated or turbocharged, remained air-cooled with additional oil cooling until in the late 1970s some turbo-charged endurance racing engines were constructed partly or completely water-cooled to be mainly used in the Porsche 956/962C sportscar racers in the 1980s. Related designs are still in use in the high-performance GT3/GT2 range. The regular 911 models used the air-cooled F6 until the 1990s Porsche 993, and starting with the Porsche 996 are fitted with a simpler and cheaper range of water-cooled engines less suited for racing.^{[10][11][12][13]}

The F6 engine is an evolution of the air-cooled flat-four Boxer engine designs by Ferdinand Porsche used in the original 1930 Volkswagen Beetle^[14][15][16] and continued by Porsche in the Porsche 356 into the 1960s.

The flat-six engine is most often associated with their 911 model, Porsche's flagship rear-engined sports car which has used flat-six engines exclusively since 1963,^[17] as the 911-bodies sold with the outgoing 356 F4 engine were called Porsche 912.

In April 2011, Porsche announced the third generation of the 997 GT3 RS with an enlarged 4.0-litre engine having a power output of 500 PS (368 kW; 493 hp). The naturally-aspirated 4.0-litre flat-six engine (the largest engine displacement offered in a street-legal 911) was introduced with their 2011 911 (997) GT3 RS 4.0, in 2011.^[18] The engine itself uses the crankshaft from the RSR with increased stroke dimensions (from 76.4 mm to 80.4 mm). This change increased the power output to 500 PS (368 kW; 493 hp) at 8,250 rpm and 460 N⋅m (339 lbf⋅ft) of torque at 5,750 rpm.^[19] giving it a power-to-weight ratio of 365 hp per ton. Only 600 cars were built.^[18][20] At 493 hp (368 kW),^[21] the engine is one of the most powerful six-cylinder naturally aspirated engines in any production car with a 123.25 hp (92 kW) per litre output.^{[22][6][23][24][25]}

Other Porsche models that use flat-six engines are the 1970–1972 Porsche 914/6 (mid-engine), the 1986–1993 Porsche 959 (rear-engine), and the 1996–2021 Porsche Boxster/Cayman (mid-engine).^[26][27][28]

The Porsche 962 sports prototype also used a twin-turbocharged flat-six engine.^{[29][30][31][32]}