If you haven't heard of him yet, we want to introduce you to Prosper L'Orange in this chapter. He was born in 1876 in Beirut, which was then part of the Ottoman Empire. In 1890 he emigrated to Germany with his parents, where he later studied at the Technical University in Berlin with great success.

He initially stayed on as an assistant at the university before moving to the Deutz gas engine factory in 1906. There he dedicated himself as a test manager to the development of a small diesel engine. It was previously only available as a large stationary engine and in 1903 for the first time on a ship. The goal of giving it a power-to-weight ratio that also made it suitable for vehicles is still a long way off.

The fact that it first powered a locomotive in 1913 shows that it was too heavy for the power required. This was due to the air injection, which in Rudolf Diesel's time was probably the only way to get the diesel fuel into the combustion chamber. It was therefore sometimes referred to as a compressor engine, but this is in no way comparable to the compressor's function today.

So the aim was to get by without the compressor with its air lines, i.e. a pump that transports the fuel directly into the combustion chamber. It's easy for it because diesel fuel has a much better lubricating effect. However, it is not easy to achieve the pressure with which to counteract the increased compression. Surprisingly, this invention is hardly mentioned in the literature except from Bosch.

L'Orange is celebrated there more as the father of the prechamber engine. His first patent for it dates from 1909. We take the text from the book 'History of German internal combustion engine construction from 1860 to 1918' by Friedrich Sass, who, only 7 years younger, can probably be considered a contemporary witness.

'An internal combustion engine for liquid fuels, in which the fuel burns immediately upon entering the engine, characterized in that the liquid fuel is ejected through a hot chamber, partially burning completely, partially decomposing and partially vaporizing and through these reactions on the way through the chamber, the pressure in the chamber increases above the pressure in the working space of the cylinder, whereby gases and vapors flow into the cylinder together with the fuel during the entire passage and thereby atomize the fuel.'

However, as with Rudolf Diesel's patent, such a chamber or the corresponding engine did not yet exist. Unlike this one, however, the first attempts are said to have been quite successful. There must have been already an injection pump with controllable injection quantity at that time. One finds an indication of 50 bar. At first glance, that doesn't sound like much, but it also shows that there were still difficulties in building such a pump.

But, the engine ran, unfortunately not very long. However, this was obviously not the fault of the injection pump, but of coking in the diesel fuel, which clogged the outlet of the nozzle. Incidentally, this was not necessarily a problem from the time of the antechamber development. From a purely physical point of view, the fuel must not be too cold, because then it will condense, i.e. return to the liquid state after it has already entered the gaseous state, but also not too hot, because then it will coke.

Long story short, L'Orange never got the problems under control and the company didn't pursue the patent after 1915. This made it was free during World War I and the work of engineer H. Leissner from a machine works in Södertaltje, Sweden, began. You will remember that this is where the first Scania-Vabis truck came from, back in 1911 it was still equipped with a four-cylinder petrol engine.

In any case, the Swedish engineer managed, in lengthy experiments, to set the temperature in the antechamber in such a way that neither condensation nor coking occurred. Professor Sass writes in his book that he personally 'was able to convince himself on the manufacturer's test bench'. Orange got wind of this after the end of the war, which then designed the cylinder head shown below and had it patented. Any subsequent quarrels we exclude here.

Even if it was not yet in one piece and screwed together, the antechamber looked roughly like it had been mass-produced for decades (picture below). It was not replaced on trucks until the 1960s and then on cars in the 1990s due to the introduction of direct injection. The crucial part bore the letter c. The nozzle sprayed into this insert at a reasonably exact angle, avoiding the remaining cooled wall of the antechamber.

The so-called collar, the part of the ignition insert c that was in direct contact with the wall of the antechamber and was able to give off its heat, was assigned to each engine type in particular. In this way, the working temperature in the antechamber could be precisely dosed. So that it was also achieved when the engine was started cold, there was already the glow plug f, which heated the interior of the vehicle battery by (sometimes quite long) preheating.