The Porsche 911 flat-six engine has six cylinders.
A flat-six, also called a horizontally opposed six-cylinder or boxer-six, places three cylinders on each side of the crankshaft. The opposing pistons help balance one another, allowing the engine to run smoothly while remaining relatively short in height. That low profile suits the 911’s distinctive rear-engine layout.
Porsche introduced the 911 in 1963, and the model has used flat-six engines throughout its history. Early engines were air-cooled, while later generations adopted water cooling, beginning with the 996-generation 911 in the late 1990s. The basic cylinder arrangement remained six horizontally opposed cylinders.
A common mix-up is confusing a flat-six with a V6. Both have six cylinders, but a V6 places its cylinders in two angled banks, whereas a flat-six spreads them horizontally. Engine size and induction have changed dramatically across 911 generations—from small naturally aspirated units to turbocharged engines—but the familiar six-cylinder layout remains a defining feature of the nameplate.