In the early 20th century, a seemingly unconventional engine design emerged as a promising avenue for automotive innovation, particularly for mass-produced vehicles. This was the slide-valve spark-ignition engine, a technology that Daimler-Motoren-Gesellschaft (DMG) embraced for nearly fifteen years with considerable success. This engine, central to the Mercedes Knight vehicles, offered a unique approach to engine performance and refinement.
Instead of traditional poppet valves, which are typically positioned overhead or upright and operated by a camshaft, these engines employed a sophisticated gas exchange mechanism. This involved two cylindrical sleeve valves situated between the cylinder wall and the piston, moving in sync with the combustion cycle. This innovative technical solution was conceived by American engineer Charles Y. Knight in 1903. Paul Daimler, DMG’s chief engineer, was captivated by the potential advantages of this design. His own intensive research into slide-valve control led to acquiring several relevant patents in 1908 and 1909. Following extensive and positive test bench evaluations, DMG secured production licenses for Knight’s slide-valve engine, recognizing its potential for their vehicles, particularly the Mercedes Knight.
The defining characteristics of the slide-valve engine were ideally suited to enhance the attributes of comfortable touring cars, especially within the premium segments of the Mercedes model range. The focus was not solely on achieving maximum horsepower, but rather on delivering a refined, exceptionally quiet operation and superior power delivery, even at the lower end of the engine speed spectrum. Conventional valve-controlled engines of that era often lagged in these aspects. The inherent drawbacks of slide-valve technology, such as sealing challenges, stringent lubrication requirements, and limitations in engine speed, were less critical given the performance levels of the time. However, with the rapid advancements in combustion engine technology, particularly in aviation during World War I, and the subsequent continuous increase in car engine speeds, slide-valve engines gradually became outdated. Their application narrowed to niche areas, and the Mercedes Knight, while innovative, would eventually be superseded.
Unveiled at the Paris Motor Show in December 1910, DMG’s inaugural production model featuring the Knight system slide-valve engine commenced production in early 1911. This Mercedes Knight model boasted a slightly long-stroke four-cylinder engine with a 4.1-liter displacement. Producing 45 horsepower (33 kW) at 1750 rpm, its performance was comparable to contemporary valve-controlled engines. The engine lineup expanded two years later to include a 2.6-liter variant producing 30 horsepower (22 kW) and a robust 6.3-liter version generating 65 horsepower (48 kW), further diversifying the Mercedes Knight offerings.
These slide-valve engines were specifically integrated into touring cars marketed under the Mercedes Knight brand. The 10/30 hp, 16/40 hp, and 25/65 hp models constituted a distinct model family within the broader Mercedes passenger car range. Despite the elevated production and maintenance expenses, along with the inherent complexity of the technology, a dedicated customer base remained loyal to these vehicles. DMG catered to this market for a total of 14 years. While production of the 10/30 hp and 25/65 hp models ceased in 1915, the 4-liter model remained in production until 1924. The overall production volume of Mercedes Knight models during this period exceeded 5,500 vehicles, demonstrating a sustained, if niche, market presence.
In mid-1913, the successful 16/40 hp model was rebranded as the Mercedes Knight 16/45 hp. Remarkably, some of these vehicles were even entered in motor racing events without any modifications to their standard engines. Théodore Pilette, the Belgian DMG importer, notably excelled in this arena, showcasing the potential advantages of the Knight engine’s unique characteristics in competitive racing.
A prime example of this was Pilette’s audacious participation in the Indianapolis 500 race, held for the third time on May 30, 1913. The Belgian driver, whose 16/45 hp racing car possessed the smallest engine capacity and lowest power output in the entire field, qualified with the slowest speed. However, the Knight engine’s inherent reliability and, crucially, its exceptional fuel economy proved decisive over the grueling race distance. Without requiring a single pit stop, Pilette achieved a sensational fifth-place finish after 7 hours and 19 minutes. Over the 500-mile race, the Mercedes Knight demonstrated an average fuel consumption of just 11.8 liters per 100 kilometers, a testament to the engine’s efficiency.
Léon Elskamp, also from Belgium, further cemented the Mercedes Knight‘s reputation in racing during 1912 and 1913. He became recognized as a skilled driver who effectively leveraged the design strengths of the Mercedes Knight. For instance, at the Ostend race week in late June 1913, he secured victory in the racing car class for engines up to 4.5 liters, achieving an impressive speed of 116.5 km/h in a 16/45 hp Mercedes Knight. These racing achievements underscored the capability and innovative engineering behind the Mercedes Knight vehicles, even as the automotive world was moving towards different engine technologies.
