Spurred on by the on-track rivalry between many of the day's major manufacturers, racing cars quickly developed from a big engine strapped to a straightforward frame to sophisticated machines until the outbreak of the Great War in 1914. Among the protagonists were Mercedes and Peugeot, who both fielded cars with four valves per cylinder during that year's French Grand Prix. While the Mercedes team won the race, the Peugeots actually featured the most sophisticated engine with dual overhead camshafts.
Although seen before on other cars, Peugeot was the first major manufacturer to set what is still the standard configuration for performance engines in 1912 with the introduction of the L76. Generally credited for the development of the engine are drivers Georges Boillot, Jules Goux and Paul Zuccarelli.
Another key figure was draughtsman Ernest Henry, who put the ideas of the three 'charlatans' on the drawing board. At 7.6 litre, the engine was small compared to Peugeot's rivals. The L76 nevertheless won the French Grand Prix in 1912 and the Indy 500 in 1913.
For 1914, a displacement limit of 4.5 litre and a maximum weight of 1,100 kg was introduced. This offered the Peugeot engineers the opportunity to further improve the twin-cam engine. The most significant change was the adoption of gears to drive the camshafts instead of the shaft previously used. As before, the block and and head were cast in one piece, while the camshafts were housed in separate aluminium carriers. This left the valve-springs and stems exposed. Breathing through a single Claudel carburettor, the new engine produced 112 bhp at 2,800 rpm.
Also following familiar lines was the steel ladder frame, which housed the 4.5 litre engine and four-speed gearbox. Suspension was by semi-elliptic leaf springs and friction dampers at both ends. New for the L45 was the use of drum brakes on all four corners instead of the rear brakes only found on the earlier Peugeots and also the rivalling Mercedes. The car was clothed in a straightforward body that offered just enough room for the driver and the riding mechanic. At least four examples were built and entered in the French Grand Prix.
As mentioned before, Mercedes won the prestigious race in large part due to longevity of Mercedes' Continental tyres compared to the Dunlop tyres used by Peugeot. Less than a week later Archduke Franz Ferdinand was assassinated; the first in a chain of events that would lead to the outbreak of World War I. As a result, all racing was suspended and the sophisticated Peugeots were not seen in action again in Europe. In the following years, most of the surviving Peugeots were shipped Stateside, where racing continued uninterrupted.
In the United States, the Peugeot L45 immediately showed its worth, scoring a win at the Indy 500 in 1916 with Dario Resta behind the wheel. During the following two years the Indianapolis Motor Speedway served as a landing strip for the military. When racing resumed, a pre-War Peugeot was driven to victory again. Peugeot did not return to racing, although the designs did live on in the Ballots penned by Henry. The L45 remains as the last of the great Peugeot racing cars that were hugely successful and influential.