Porsche flat-twelve engine

The Porsche flat-twelve engine is the series of twelve-cylinder boxer engines that Porsche built for its 917 sports prototype between 1969 and 1973. The Type 912 was designed by chief engineer Hans Mezger under Ferdinand Piëch and Helmuth Bott as a 4.5 litre air-cooled unit that combined two of the 2.25 litre flat-six racing engines, with twin overhead camshafts driven from central gears and twin spark plugs. It was Porsche's first twelve-cylinder engine and used titanium, magnesium and exotic alloys. Early engines made about 520 horsepower and later ones reached 630 horsepower at 5 litres. Twin-turbocharged versions followed for the Can-Am series, where the 917/30 with a 5.4 litre engine made around 1,100 horsepower in race trim.