Air and fuel for the engine: The carburettor

From the first pioneering vehicles until late into the 1980s - the carburettor is an integral part of engine technology. As a system for mixture formation, it is responsible for providing the air-to-fuel mixture for the combustion process in the engine. This means that, in a sense, the carburettor acts as a "lung" for the vehicle engine. The biggest manufacturer and supplier by far at this time is Deutsche Vergaser Gesellschaft based in Berlin, and Neuss from 1947, which operates under the name Pierburg from 1978.

In the first few decades of car travel, the long list of carburettor manufacturers becomes as confusing as the number of car manufacturers. The list ranges from A for Amal right through to Z for Zenith. But only a few models and design variants will stand the test of time. One of these is the carburettor designed in 1908 by Marcel Mennesson, an engineer from the Société Solex in Paris, and patented in 1910. In the years that follow, this Solex carburettor takes over the automotive world and plays a major role in the history of Pierburg – at least until the carburettor technology is replaced by the fuel injection systems in use today.

Pierburg is a pioneer for large-scale carburettor production in Germany. The potential for the carburettor that lies in the motorisation of the relevant vehicles on the road, water and air is identified early on.

Start of carburettor production in Berlin

The skill and personal commitment shown by Bernhard Pierburg and his son Alfred in the fight for the Solex carburettor licence form the basis for an unprecedented success in German automotive supplier history. Step-by-step, Gebr. Pierburg AG grows into the largest carburettor manufacturer in the German Reich.

Even the looming global economic crisis does not alter the lasting success of the German Solex carburettors. The problems faced by Pierburg's main bank also threaten the existence of Gebr. Pierburg AG and the company's shares are taken over by a trust company. But Bernhard Pierburg manages to salvage the carburettor licence and the production site based in Heidestraße from Gebr. Pierburg AG. In 1931, they are incorporated into a newly founded company in Berlin under the name Deutsche Vergaser Gesellschaft (DVG). The company is run by Alfred Pierburg from this point on.

In just a short time, Alfred Pierburg manages to get Solex carburettors installed in renowned German vehicles and they are quickly established as the number one on the German carburettor market.

Post-war era: Carburettors from Neuss

The plant in Berlin is destroyed during the Second World War and the power of disposition is taken away from the Pierburg family. It is taken over by former employees, who follow their own business concept. There is also some initial confusion concerning the Solex licence. However, as the British occupying forces also need a carburettor expert to fit and repair their military vehicles, they are reliant on the know-how of Alfred Pierburg. In 1946, the British headquarters confronts the managers in Berlin with a completely new situation: The company in Heidestraße is handed back to the Pierburg family. This includes the most important DVG asset of all: the carburettor licence, which, according to the wishes of the French owner, is now assigned to Alfred Pierburg personally.

While carburettor production is started up again in Berlin, Alfred Pierburg establishes a new operation in Büdericher Straße in Neuss. Work begins there in 1947.

And the Solex carburettors once again conquer the German automotive market: The major customers are Mercedes-Benz, BMW, Ford, Glas, Borgward, Goliath – and, of course, VW. In the first few years, DVG only reproduces the original Solex designs. But technology continues to develop. Pierburg and his employees therefore soon start to incorporate their own research results in new designs. The issue of "carburettor freezing" is addressed, as well as the behaviour at different altitudes. The conventional choke is replaced with an automatic choke. In 1956, the PAITA model becomes the first two-stage carburettor to enter high-volume production. It fulfils the demand for good mixture formation in the lower engine speed range and higher mixture flow rates for full engine performance.

A new development focus also emerges: reducing the pollutant emissions of the vehicle. The strict regulations governing exhaust gas emissions introduced in the USA in the 1960s force the design engineers to develop special "exhaust gas carburettors", which lead to a significant reduction in CO, HC and NOx emissions.

Developments in carburettor technology

Since the invention of the Solex carburettor by Marcel Mennesson in 1910, the technical principle has not changed significantly. The term "carburettor" stems from the early era of this technology and is actually misleading. The correct term is "mixture controller": Air and fuel are metered for each operating state, the fuel is atomised as finely as possible, mixed with the air and finally fed through the intake manifold into the cylinder according to the required engine performance. But while this may sound extremely simple, constant development is required to improve the functionality and to adapt the manufacturing technology to the increasing volumes.

The first Pierburg carburettor for Hanomag is still produced using the sand casting method from brass. Only the switch to pressure die casting and zinc as the material enable large-scale production from 1930. Significant improvements in the choke are also made at this time: The first updraft and horizontal carburettors supply a metered fuel-air mixture to the engine via starter rotary slides for the first time.

Developments in the field of the carburettor continue in leaps and bounds after the Second World War. Equal importance is place on driving comfort and driving performance, as well as reducing fuel consumption and emission control. The use of dual carburettors leads to improved engine performance. A carburettor with automatic choke replaces the conventional choke for the first time in the Beetle in 1959.

1968 sees the launch of a milestone in the form of a CD downdraft carburettor based on a US Bendix-Stromberg patent. The innovation, with aluminium housings cast by Kolbenschmidt in Neckarsulm and Hamburg, moves away from the previous fixed nozzle principle for the first time. Now, large air flows can be achieved for maximum speeds with just one variable nozzle system, without compromising on the good transitions in the lower engine speed ranges. Developments are also made in the use of acceleration pumps and load-point specific enrichment of the air-petrol mixture.

But gradually, the growing competition from injection begins to have an impact on the carburettor: The new generation with the types Zenith 1B, 2B or 2E is already designed for electronic control loops.

The end of the carburettor era

In 1967, Alfred Pierburg is still convinced that "injection drivers are snobs". But the impact of the advancing
injection technology is unstoppable. The injection already established in diesel engines is also becoming a marketable alternative to the carburettor for petrol engines. And there are many arguments in its favour. Fuel injection systems create the necessary conditions for operating-point dependent control of the combustion process. This increases the energy efficiency of modern cars considerably.

There is a major divide at Pierburg. The heart of the company is with the original carburettor business. But DVG attempts to bring an injection system developed by Solex to series maturity in 1969. Three years later, in 1972, DVG even presents its own Zenith race injection system. Although the system is highly praised by the trade press, it remains a one-off. While the performance speaks in favour of injection, the costs do not compare with those of the carburettor.

Over time, however, injection becomes cheaper and more powerful, while the carburettor
becomes more complicated and expensive. The automotive companies focus on enhancing their engines and injection becomes synonymous with modern technology. In 1983, 34 percent of German petrol engines are already equipped with injection systems – and the number is rising. Pierburg's final attempt to assert itself on the carburettor market is the joint development of an electronically controlled carburettor in the Bosch-Pierburg-System Gesellschaft (BPS) partnership.

This highlight in the development of the carburettor also heralds its end. The technically complex system is not accepted in the market, development is ceased in 1987. In 1992, with over 75 million carburettors produced at Pierburg over the years, the launch of controlled three-way catalytic converters brings the definitive end: Pierburg must embark on a new path to compensate for the collapse of the carburettor business.
 

1928 First Solex carburettor manufactured in Berlin
1929 First dual carburettor for luxury saloons
1931 Deutsche Vergaser Gesellschaft is founded
1947 New start for Pierburg in Neuss
1955 Construction of the APG plants in Düsseldorfer Straße in Neuss
1956 First Solex two-stage carburettor
1959 First carburettor with automatic choke
1967 First effects of the emissions laws in the USA
1975 The carburettor plant in Nettetal is purchased
1969 A research and development centre is established
1972 Start of a new carburettor series
1981 Presentation of an electronic carburettor
1989 Decision to launch the three-way catalytic converter
1995 End of the Pierburg carburettor series production in Europe

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