Porsche six-cylinder boxer engine – the sports car engine

The six-cylinder boxer engine is an essential aspect of the legendary 911. It boasts almost unlimited potential thanks to its basic concept, which remains unchanged to this day.

Even before the 911 had taken shape, one thing was for certain: it was going to feature an air-cooled boxer engine with six cylinders. This met all the requirements relating to a sports car engine and boasted a sleek design that guaranteed the car a low centre of gravity for optimum driving dynamics. The underfloor assembly ensured the largest possible amount of usable space in the body. Due to the lack of inertia forces and free moments of the first and second order, the principle of the six-cylinder boxer engine also delivered maximum smoothness.

Comprising eight bearing positions, the crankshaft was fully prepared for taking on high bending stresses at extreme speeds. The presence of an elevated camshaft on each side helped increase the speed reserves and the level of smoothness. The camshaft drive featured the use of chains, with vertical shafts and toothed belts having previously been ruled out. The cubic capacity was initially defined at two litres and a potential increase to as much as 2.7 litres was planned from the start. Delivering 130 horsepower, this six-cylinder boxer engine began its unprecedented career with the internal designation ‘type 901/01’. In the early 1960s, no-one could have predicted that this engine type would continue in its basic form until 1998 – or that the cubic capacity would ultimately reach a level of 3.8 litres.

The boxer engine remained air-cooled until after the launch of the 993 generation. When the engineers made the switch to water cooling in 1997, this had a wide-ranging impact – and helped tap into new performance classes. This development, which initially proved controversial within the Porsche community, was soon celebrated as a step forward. Featuring a cubic capacity of 3.4 litres and delivering 221 kilowatts (300 horsepower), it was considerably shorter, flatter and much more free-revving than the previous engine. This also marked the first time that the gas exchange in the 911 had been controlled by four valves per cylinder.

In 2008, the boxer engine was almost entirely reinvented. A one-piece crankcase with integrated crankshaft bearings replaced the two-piece block with separate bearing casing that had previously been used. The crankshafts, the geometry of the combustion chambers, oil pump and water pump, and the entire intake area were also redesigned. Compared with their predecessors, the new engines achieved a weight saving of around six kilograms. In addition, the redesign process saw Porsche introduce direct petrol injection. All current 911 engines are enhanced versions of this engine.

Go back

next page
Mid-engine sports cars — the ultimate in driving dynamics