Porsche flat-six engine

The Porsche flat-six engine series is a line of mechanically similar, naturally aspirated and sometimes turbocharged, flat-six boxer engines, produced by Porsche for almost 60 consecutive years, since 1963.^[8][9] The engine is an evolution of the flat-four boxer used in the original Volkswagen Beetle.^[10][11][12]

Porsche flat-6 engine
Overview
Manufacturer	Porsche
Production	1963–present
Layout
Configuration	flat-6
Displacement	2.0–4.2 L (122–256 cu in)[1]
Cylinder bore	80–102.7 mm (3.1–4.0 in)[2][3]
Piston stroke	66–80.4 mm (2.6–3.2 in)[4][5]
Valvetrain	12-valve to 24-valve, SOHC/DOHC, two-valves per cylinder to four-valves per cylinder[6]
Combustion
Turbocharger	Yes (some models)
Fuel system	Mechanical fuel injection Carburetor Direct fuel injection
Fuel type	Gasoline
Oil system	Dry sump
Cooling system	Air-cooled[7] Water-cooled
Output
Power output	110–850 hp (82–634 kW)
Torque output	119–730 lb⋅ft (161–990 N⋅m)
Dimensions
Dry weight	387–507 lb (176–230 kg)

1967 Porsche 911R

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2006 Porsche Cayman S

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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.^[13] The engines were air-cooled until 1999, when Porsche started using water-cooled engines.^{[14][15][16][17]}

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 offered in a street-legal 911) was introduced with their 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]}