Bentley 4½ Litre

The Bentley 4½ Litre is a British car based on a rolling chassis built by Bentley Motors. Walter Owen Bentley replaced the Bentley 3 Litre with a more powerful car by increasing its engine displacement to 4.4 litres (270 cubic inches). A racing variant was known as the Blower Bentley.

Bentley buyers used their cars for personal transport and arranged for their new chassis to be fitted with various body styles, mostly saloons or tourers. However, the publicity brought by their competition programme was invaluable for marketing Bentley's cars.^{[citation needed]}

At the time, noted car manufacturers such as Bugatti and Lorraine-Dietrich focused on designing cars to compete in the 24 Hours of Le Mans, a popular automotive endurance course established only a few years earlier. A victory in this competition quickly elevated any car maker's reputation.

A total of 720 4½ Litre cars were produced between 1927 and 1931, including 55 cars with a supercharged engine popularly known as the Blower Bentley. A 4½ Litre Bentley won the 24 Hours of Le Mans in 1928. Though the supercharged 4½ Litre Bentley's competitive performance was not outstanding, it set several speed records, most famously the Bentley Blower No.1 Monoposto in 1932 at Brooklands with a recorded speed of 222.03 km/h (137.96 mph).

The 24 Hours of Le Mans endurance race is a 24-hour race around the Circuit de la Sarthe. The inaugural race was held 26–27 May 1923, and attracted many drivers, mostly French. There were two foreign competitors in the first race, Frank Clement and Canadian John Duff, the latter winning the 1924 competition in his personal car, a Bentley 3 Litre.

"Made with precision and the finest material," and with recent success, the luxurious Bentley cars attracted attention. After two years without success, Bentley convened a group of wealthy British men, "united by their love of insouciance, elegant tailoring, and a need for speed," to renew Bentley's success. Both drivers and mechanics, these men, later nicknamed the "Bentley Boys", drove Bentley automobiles to victory in several races between 1927 and 1931, including four consecutive wins at the 24 Hours of Le Mans, and forged the brand's reputation.

It was within this context that, in 1927, Bentley developed the Bentley 4½ Litre. Two cylinders were removed from the 6½ Litre model, reducing the displacement to 4.4 litres. At the time, the 3 Litre and the 6½ Litre were already available, but the 3 Litre was an outdated, under-powered model and the 6½ Litre's image was tarnished by poor tyre performance.

Sir Henry "Tim" Birkin, described as "the greatest British driver of his day" by W. O. Bentley, was one of the Bentley Boys. He refused to adhere strictly to Bentley's assertion that increasing displacement is always preferable to forced induction. Birkin, aided by a former Bentley mechanic, decided to produce a series of five supercharged models for the competition at the 24 Hours of Le Mans; Mercedes-Benz had been using superchargers for years.