Sunbeam 3-litre
| Industry | Automotive |
|---|---|
| Headquarters | United Kingdom |
| Products | Automobiles |
The Sunbeam 3-litre is a sports automobile launched by the Sunbeam in October 1925 during the London Motor Show, with production spanning from 1926 until 1930. This model was engineered by Louis Hervé Coatalen, Sunbeam’s chief engineer, to rival the Bentley 3 Litre, which had earned acclaim earlier that year by winning the 24 Hours of Le Mans endurance race.
Equipped with a 2,920 cc straight-six engine, the vehicle incorporated inclined valves controlled by dual overhead camshafts, representing a sophisticated engineering approach for its era. The engine featured a unified casting for both the cylinder head and block, adopting racing techniques that had contributed to Sunbeam’s success on European tracks. It utilized dry-sump lubrication complemented by an external oil reservoir. In 1929, the addition of a supercharger elevated the power output to 135bhp.
The engine’s bore size corresponded to a fiscal horsepower rating of 20.9 hp, resulting in an annual Road Fund Tax liability of £21. This tax was greater than that imposed on Bentley’s similar four-cylinder engines, which attracted £16 per year, potentially affecting the overall cost of ownership despite the Sunbeam’s positioning as a premium vehicle.
Although Bentley was often perceived as more durable, the Sunbeam offered slightly superior speed in its standard configuration. At the 1925 Le Mans event, two Sunbeam entries participated: Henry Segrave and George Duller retired early, while Jean Chassagne and Sammy Davis achieved second place behind the winning Lorraine-Dietrich team. Nonetheless, Bentley’s subsequent dominance in endurance racing eventually eclipsed this performance.
The chassis design originated from earlier Sunbeam models but innovated by replacing conventional semi-elliptical rear leaf springs with cantilever rear springs—a suspension feature that became emblematic of Sunbeam vehicles in later years.