Ninetieth anniversary of diesel breakthrough

It's been 90 years since German truck maker MAN first pioneered the breakthrough of direct injection in a diesel-engined truck

This year sees MAN Truck & Bus celebrate the 90th anniversary of the development of diesel direct injection, which was pioneered by the German trucking giant and first trialed in 1924.

While Rudolf Diesel first patented the diesel engine in 1897, early forms were only employed in factories or on ships on account of their large size and high weight. MAN's engineers intensified their efforts to develop a vehicle-friendly diesel engine from 1919, and in 1924 first fitted an experimental direct injection diesel to an MAN Saurer truck (pictured, both in original and restored form).

MAN engineers Sturm and Wiebicke set off in the 40hp vehicle on March 12, 1924, and completed a 140km test run from Augsburg to Nuremburg in around five-and-a-half hours. Little did they know at the time, but it was a seminal moment in the evolution of automotive world.

Bernd Maierhofer, Executive Board Member for Research & Development at MAN Truck & Bus, outlines the gravity of the development.

"The first MAN with diesel direct injection represents a milestone in engine technology," he says.

"You can still see its massive impact today: every modern diesel engine, whether it be for a car or truck, uses the principle of direct injection. Its latest incarnation is common-rail injection. We use it in all MAN diesel engines as it allows us to efficiently control the combustion process in the cylinder."

Direct injection, which dispensed with the heavy and power-sapping high-pressure compressors of the day, saw combustion air heat up as it was compressed in the cylinder head by the upward movement of the piston, before a mechanical injector forced fuel into the compressed air. The precision-engineered injection valve, manufactured by MAN, atomised the fuel and increased its combustability, while the high temperature of the gas caused the mixture to ignite.

The Saurer test truck completed 2500km before it was shown at the Berlin Motor Show over December 10-18, 1924, and Sturm insisted on driving it there from MAN's Nuremburg facility – a journey it completed without incident.

The innovation caused a sensation at the show, prompting the magazine of the German Association of Engineers to write: "In the whole field of lorry engines and associated fuel matters, the MAN compressor-free diesel engine is surely the most significant innovation ever to be seen at the exhibition."

Not long after the first customer delivery of a direct-injection diesel-engine truck was made to the 'zum Hasen' brewery in Augsburg (pictured, with kegs) – and the modern diesel was set on its path to global success.

Ninetieth anniversary of diesel breakthrough

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