Puffer Injection

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The Kugelfischer injection system , also known as the “Kugelfischer System”, is a mechanical manifold injection system for gasoline engines offered by the company “ FAG Kugelfischer Georg Schäfer ” from the early 1960s . The system was not developed by FAG in Schweinfurt , but by the Munich company Schäfer-Einspritztechnik GmbH, which was taken over by FAG-Kugelfischer . This in turn was able to fall back on their experience in the manufacture of injection pumps by joining Friedrich Deckel AG .

The fuel metering takes place only by changing the piston stroke of the injection pump ("Schäfer pump") and is not dependent on the amount of air drawn in . Therefore, a basic requirement for good engine running is an exact synchronization of the injection pump with the throttle linkage or the throttle valve position.

functionality

Kugelfischer-Pump PL 04 from a BMW 2002 tii
Opened Kugelfischer PL 04 with space cams, opened swing arm and piston

The fuel is delivered to the Kugelfischer injection pump by a separate electric fuel pump , which is located near the fuel tank and generates a system pressure of approx. 1.2 bar.

The injection pump mounted directly on the engine is usually connected to the engine's oil circuit and is driven mechanically by a toothed belt or chain or a spur gear. It has one delivery piston per engine cylinder. The fuel reaches the injection pump cylinder above the delivery piston and is delivered by this during the first working cycle to the injection valve mounted in the intake manifold. This valve is spring loaded; at a certain pressure it opens and the gasoline is injected. In order to prevent the fuel from flowing back, there are check valves in the injection pump (suction or pressure valves). The excess, i.e. H. Non-injected petrol also cools the injection pump to prevent vapor lock formation. It is fed back into the tank via its own return line.

Since the engine requires different amounts of fuel depending on the operating status (see also combustion air ratio ), an appropriate control is required. This is done by adjusting the stroke of the delivery pistons, the bottom dead center of which is varied, which changes the volume of fuel taken up by the pump cylinders. For this purpose, the pump pistons lie at the bottom on a single-sided swing arm, the position of which defines the injection quantity. If the rocker is low, the piston stroke is long, if it is high, the piston stroke is smaller. The other side of the rocker rests with a stylus on the core of the pump, the so-called "space cam", which ultimately defines the injection quantity. This space cam, also known as a "potato", is an elongated cone that has raised areas or depressions all around for the various operating states of the engine. The engine map is mapped like this in a current map ignition . As the throttle valve position changes, the space cam moves along the cone slope, which changes the stroke of the delivery piston. As the speed increases, the cone rotates around its axis and thus also changes the injection quantity. This system is supplemented by facilities for the cold start , the warm-up phase and an adjustment to the changing air pressure at changing altitudes.

The space cam must be specially developed for the respective engine type. For this reason, without changing the space cam, no significant changes to the intake tract or z. B. possible with the timing of the camshaft, because then the optimal fuel-air ratio can no longer be achieved due to the fixed injection quantity.

The functioning of the pumps is identical for 4 and 6 cylinder engines.

commitment

The first use of the Kugelfischer injection was in motorsport . Appropriate injection systems were used in touring car, formula or circuit races and rallies. Advantages such as speed stability, precision of the injection quantity and mixture throughput made the system particularly interesting for high-performance engines. At that time and in this context, the clear consumption advantages were of secondary importance. The system was mostly used here together with single throttle or flat slide valve systems. These systems based on the BMW M10 four-cylinder engine were very popular , from Formula 2 to the 1,350 hp BMW Formula 1 engine with turbocharging (M12 / 13) in the 1980s. Some of these systems are still in use in motorsport to this day.

The system was also used in high-performance series vehicles. Examples are:

The first mass-produced motorcycle with intake manifold injection , the Münch-4 TTS-E 1200 from 1973, also had a Kugelfischer injection.

Some tuners active in racing developed roadworthy systems based on these engines. So built z. B. Alpina, a version based on the engine of the BMW 2002 tii (130 hp), which had an injection system with self-developed individual throttle valves (Alpina A4), which, depending on further measures, led to an increase in performance to approx. 155-190 hp. Alpina also had a similar system for the BMW 3.0 CSL (250 instead of 180 hp), but in individual production, as was the case with other manufacturers for the NSU TT or the Ford Capri .

Manufacturing and spare parts supply

The Kugelfischer injection systems division was taken over by Robert Bosch GmbH in 1979 . The manufacture became increasingly unattractive due to the increasingly cheaper electronic injection systems to manufacture. Bosch supplied the spare parts for the systems until 1989, then the Bosch service Koller + Schwemmer GmbH in Nuremberg took over all documents, machines and spare parts and ensured the parts supply. In 2012, the Bosch Automotive Aftermarket division bought Koller + Schwemmer GmbH, which is now an independent subsidiary of Bosch Classic Car Service .

literature

  • Oldtimer Market : The Competitors - Injection Technology, Part 2: The Systems by Kugelfischer, Lucas and Spica , Issue 9 (September 2001), VFW Verlag für Wirtschaftsmedien, Mainz
  • Kugelfischer gasoline injection pump with pneumatic regulator type KF5 Peugeot description (pdf, 5.9 MB)

Web links

Individual evidence

  1. ^ Hans J. Schneider: BMW 5 Series - technology + types, models up to 1997; Bielefeld 2007, ISBN D / A / CH 978-3-7688-5789-5, page 16.