Porsche 911—flat-six
Porsche’s first sports car, the 356, utilized many components from the Volkswagen, including its flat-four engine. When an all-new power plant was needed for the replacement 911, Porsche kept the horizontally opposed layout and air-cooling but upped the cylinder count to six. The result was one of the most charismatic and enduring high-performance engines of all time.
LASTING SUCCESS
It is a measure of the quality of Porsche’s original design that the flat-six remained in production—through numerous variants of increasing capacity, including fearsome turbocharged units—for more than three decades. The 911 refused to die, and its unique engine with it. While the 911 continues, the engine was eventually replaced in 1998, when Porsche retained the flat-six layout but abandoned air cooling for water cooling. One of the benefits was that, for the first time in the 911, Porsche was able to use four valves per cylinder and exploit the improved engine “breathing” (air flow) that resulted.
ENGINE SPECIFICATIONS
| Dates produced | 1963-1998 (air-cooled version) |
| Cylinders | Flat-six |
| Configuration | Rear-mounted, longitudinal |
| Engine capacities | 1,991 cc, progressively increased to 3,746 cc |
| Power output | 128 bhp @ 6,200 rpm (ultimately 402 bhp with twin turbos) |
| Type | Conventional four-stroke, air-cooled, gas engine with reciprocating pistons, distributor (later distributorless) ignition, and a wet sump |
| Head | sohc per bank, chain driven; two valves and (later) twin spark plugs per cylinder |
| Fuel System | Single carburetor, later fuel injection |
| Bore and Stroke | 3.15 in x 2.60 in (80 mm x 66 mm) |
| Power | 64.3 bhp/liter |
| Compression Ratio | 9.0:1 |
Six beats four
By the early 1960s the Porsche flat-four engine, used in the 356, had exhausted its development potential. Its flat-six replacement released the extra power the new 911 model would need. The engine’s design allowed for progressively increased engine capacity as Porsche further developed the 911.
Low profile
Although the cylinders and crankcase are obscured in this photo of a 1994 flat-six, the engine’s low, wide stance is obvious. This helps the engine fit neatly into the tail of the 911, while the lowered center of gravity aids roadholding.
It is a quote. The Definitive Visual History Of The Automobile 2011
