The Bentley 4½ Litre is a British sports car built by Bentley Motors. Replacing the Bentley 3 Litre, it is famous for epitomizing prewar British motor racing and for its popular slogan "there's no replacement for displacement", created by the founder of Bentley, Walter Owen Bentley. Bentley sought to produce a more powerful race car by increasing engine displacement.
At the time, noted car manufacturers like 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 were produced between 1927 and 1931, including 55 models with a supercharged engine known as the Blower Bentley. Some of these Bentleys did win a few competitions, including the 24 Hours of Le Mans. Though its overall competitive performance was not particularly outstanding, the 4½ Litre Bentley managed to beat several speed records, most famously in 1932 at Brooklands with a recorded speed of 222.03 km/h.
The most significant difference between the Bentley 4½ Litre and the Blower is the engine. The Blower engine is supercharged by a mechanical compressor designed by engineer Charles Amherst Villiers. W.O. Bentley, being hostile to forced induction, believed that "to supercharge a Bentley engine was to pervert its design and corrupt its performance." He refused to allow the engine to be modified to incorporate the compressor; the latter is therefore placed at the end of the crankshaft, in front of the radiator, giving the Blower Bentley a unique and easily recognizable profile and exacerbating its understeer.
A guard protects the carburetor, now located near the compressor, and the headlights are exposed to shocks. Similar protection is used (both in the 4½ Litre and the Blower) for the gas tank at the rear, because a flying stone punctured the 3 Litre of Frank Clement and John Duff during the first 24 Hours of Le Mans, possibly depriving them of victory.
Villiers chose a Roots type supercharger. The weight of the crankshaft, another set of pistons and a piston lubrication dry sump, nevertheless, are adapted to the engine. Supercharged, the Blower Bentley produces 175 hp (130 kW) at 3,500 rpm for the Touring model and 240 hp (177 kW) at 2,400 rpm for the racing version--more powerful than the Bentley 6½ Litre despite lacking the two additional cylinders