Few manufacturers are known as well for a singular engine as Porsche and their flat-six. Since 1963, the Porsche flat-six motor has seen continuous usage in their flagship vehicles, powering some of the most renowned Porsches of all time. Despite other manufacturers shifting towards more common “V” and inline options in the name of cost and reliability, the flat-six has stood the test of time for the storied German automaker. In this article, we’ll cover why the flat-six is such a mainstay in Porsche’s model lineup, what separates them from other engines, and why the flat-six isn’t found in more vehicles today.  What is a Flat-Six Similar to how the “V” and “Inline” prefixes of other engines represent the shape and layout of the engine, the “flat” in flat-six tells you a lot about the engine’s configuration.  Flat engines are similar to “V” engines such as V6s and V8s in the sense that they use two separate banks of cylinders. A flat-six will have two banks of three cylinders just like a V6 motor, however, what separates them is the angle of the cylinders rather than the amount. A traditional V6 engine will have each cylinder bank angled 90 degrees away from the other, creating the “V” shape we use to refer to the engine. A flat-six, however, lays the cylinder banks completely flat and opposite of each other at a 180-degree angle.  While this may not seem like it would make a large difference, the characteristics of flat engines differ considerably compared to a “V” or inline engine. Porsche’s flat-six is also a boxer-style flat engine, which is a type of flat engine that uses individual rod journals (AKA crank pins) for each piston rather than shared journals between opposite-facing pistons. The boxer name is most commonly used to refer to Subaru’s flat-four Boxer motor, but the term refers to any flat motor using individual rod journals.  History of the Porsche Flat-Six It’d be irresponsible to dive into the details of the Porsche flat-six without covering its interesting backstory and importance to the company.  It’s fitting that the person who brought the flat engine into relevance is none other than Ferdinand Porsche himself, who installed a four-cylinder version of the engine into the original Volkswagen Beetle.  The story begins at the dawn of the 20th century. Following a merger of Porsche’s employer Daimler-Austro and Karl Benz’s Benz & Cie brand, Porsche became frustrated at the lack of opportunity to produce the lightweight sports cars he envisioned and promptly left the newly-created Daimler-Benz. After receiving a contract with the German government in the early ‘30s to engineer “the people’s car,” Porsche would take what he learned about flat-engine designs from airplane engines designed by Karl Benz and apply it to this new project. Porsche knew a horizontally opposed, cheap-to-produce, and easy-to-maintain engine would be the perfect choice for a vehicle intended to bring the convenience of automobiles to the middle class.  Porsche would make the decision to mount the engine in the rear of the vehicle for superior weight balance, a choice that has echoed through Porsche vehicles ever since. Not once has the 911 been produced without a rear-mounted engine, and the layout has become a defining feature of the flagship sports car.  You probably know what happens next already, as the Beetle would go on to be the most ubiquitous vehicle Europe has ever seen and define the automotive industry of post-war Germany for decades to come.  It was Porsche’s son, Ferry, who moved the Porsche name away from mass-produced commuter vehicles and into producing a true lightweight sports car in 1948, the Porsche 356. The 356 was built on the Beetle platform, maintaining the rear-engined design while improving handling and engine performance.  Following the success of the 356, Ferry Porsche introduced the world to a new rear-engined vehicle in 1963 that they would come to know very well: the 911. Shipping initially with a 2.0L air-cooled flat-six making 130 horsepower,  the 911 would go on to win the hearts of drivers everywhere over its now more than half century of production and innovation with no end in sight. The flat-six would become an integral feature of the vehicle, and Porsche continues to iterate and improve the engine with each new 911 model.  Why Does Porsche Use the Flat-Six? Beyond staying true to its roots, Porsche has a few good reasons to maintain the development and production of flat-six motors. For one, the flat layout keeps the engine’s weight low to the ground, lowering the entire vehicle’s center of gravity and improving handling and control. V-shaped and inline engines have taller vertical footprints, which pushes the center of gravity higher and leads to more sway and momentum as the chassis moves during cornering. These go-kart-like handling dynamics have become a highly-praised characteristic of 911s.  Boxer flat-sixes also have the benefit of perfect balance, which keeps the vehicle running quiet and smooth through the entire rev range. This is accomplished through the use of individual rod journals, which allow for opposite pistons to extend at the same time and cancel out the horizontal force of the other side. This perfect balance makes 911s a truly unique driving experience, as the engine screams to 9K RPM with little to no vibration. Compare this to a non-boxer flat engine, which will experience imbalance due to the inability of opposite pistons to extend together. With shared rod journals, opposite-facing pistons can only extend one piston at a time, forcing the other piston to retract in response. This means the engine is unable to cancel out its own horizontal motion, leading to vibrations and imbalance.  Why Isn’t The Flat-Six Used By Other Manufacturers? The simple answer to why the flat-six isn’t a more popular option among automakers comes down to the fact that there’s no defining reason to spend the research and development costs involved in producing one. While bringing some real benefits to the table, there’s nothing in particular about the flat-six