Porsche and its tradition of flat engines: what makes these engines special?



When people think of Porsche, the first thing that often comes to mind is the silhouette of the 911 – and the dead engine. These engines are dear to the hearts of all Porsche enthusiasts. But what is so special about this particular design principle for an internal combustion engine?

The history of flat engine design dates back to 1896, when Carl Benz created what he called a “counter engine,” due to its two cylinders working in opposition to each other.

3.0-liter twin-turbo flatbed engine producing 420 hp (309 kW)


This first boxer engine was intended to have a displacement of more than 1.7 liters and to deliver 5 hp. Its underlying design principle – both then and today – is that the cylinders should lie flat, and slightly offset from each other, on opposite sides of the crankshaft. The Porsche family tree of flat engines dates back to the VW Beetle. Its 1.1-liter four-cylinder engine developing 26 kW (35 hp) was installed by Ferry Porsche in its 356-001.

Other engines followed, all air-cooled until the 911 Type 993. In the top-of-the-line 911 Carrera RS, the 3.8-liter air-cooled flat engine achieved 221 kW (300 hp) without a turbocharger. Two turbochargers increased performance to 331 kW (450 hp).

Principle of operation

The beauty of this air-cooled engine is that it is flat and light and especially low-cut designs are possible because the cylinders are flat, making it an ideal choice for sports cars – especially those which are low, like the Porsche 911 does. This lowers the center of gravity, allowing for a sportier and more dynamic driving style, and not just when cornering.

Porsche 911 Gt RS_ 3.8 liter bi-turbo

The 3.8-liter twin-turbo six-cylinder boxer engine of the 911 GT2 RS

The perfect choice for a sports car

If the flat engine is installed at the rear as in Porsche vehicles, traction is improved as the weight of the engine rests on the drive axle. Until all-wheel-drive vehicles conquered the roads, Beetle and Porsche drivers agreed that a car with a rear-mounted engine was by far the best choice for winter conditions. The reverse is also true: when braking, the weight of a rear-mounted motor allows more braking force to be transferred to the rear wheels.

The flat engine – and in particular its six-cylinder variant – is particularly smooth, with no free moments or free forces. The crank mechanism is ideally balanced, allowing short-stroke sports engines to run at high speed without excessive strain.

One of the most characteristic features of Porsche six-cylinder flatbed engines is the decrease in fuel consumption as the engine power increases. The underlying concept of the flat engine involves a lightweight and cohesive construction, a low center of gravity, exceptional revving capability and high specific power through advantageous load cycles. All 911 engines must be both sporty and suitable for everyday use.

Typically, it takes more effort to build a flat engine than an in-line engine because more parts are needed. The flat engine needs two rows of cylinders with a valve train, plus cooling or injection. The flat engine is a particularly good candidate for air cooling because the individual cylinders are spaced apart from each other and therefore can benefit from a direct flow of cooling air.

The fact that 911 flat engines have been water-cooled since the 996 model series is mainly due to the four-valve technology. Four valves are a prerequisite for reducing fuel consumption and exhaust emissions while improving performance. But that’s just a point of interest for fans of water-cooled flat engines.

Read also : Porsche 911 Targa: A Detailed History of the Evergreen Sports Car

Today’s Porsche six-cylinder flatbed engine is a smooth-running machine that also reduces fuel consumption as engine power increases. After all, it makes sense that the engine that powers the 911 would be suitable for everyday use in addition to an exhilarating driving experience.


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