The Bentley 4.5 litre was an upgrade from the Bentley 3.0 litre. 720 Bentley 4.5 litre cars, with various body styles, were produced between 1927 and 1931.

A special variant of the basic 4.5 litre was the supercharged version of which 55 were produced. W.O. Bentley, the car firms owner, was adamant that the way to increase the power of an engine was to increase the swept volume, in other words increase it's capacity. Sir Henry 'Tim' Birkin, one of Bentley's 'Bentley Boys', a select group of drivers and mechanics that had been gathered by Bentley to establish Bentley Motors as a winning firm, decided to challenge W.O. Bentley's assertion and developed a forced induction version of the engine by means of adding a compressor to increase the pressure, density and temperature of the air going into the cylinders. Bentley flatly refused to modify the engine to accommodate the new supercharger so Birkin simply placed the supercharger at the front of the chassis, giving the car its characteristic look.

The Bentley is most remembered for victories at Le Mans and other prominent races between 1928 and 1930. The Bentley was a big car with a big thirst, consuming around 4 litres every minute when at top speed. After coming second to a Bugatti Type 35 in the French Grand Prix of 1929 the Bentley Blower was described as the "fastest truck in the world".

Production ceased in 1931 when Bentley Motors was sold to Rolls Royce.