D-Jetronic

from Wikipedia, the free encyclopedia

The D- Jetronic was 1967, the first electronic ( d jerk controlled) multi-point fuel injection (multipoint injection) for four-stroke gasoline engines of Bosch , who still build their patent was later sold to Japanese companies injection systems according to this principle. It is based on the Electrojector system from Bendix Corporation , which never made it into mass production. To introduce the D-Jetronic, Bosch had to fall back on Bendix patents, for which a license agreement was signed in July 1966.

commitment

The first production vehicle with D-Jetronic was the VW 1600 LE / TLE (Type 3) , which was produced from 1967 . Later it was also used in the VW models 411 E / 412 E (Type 4) , the VW-Porsche 914/4 and the Porsche 912 E.

Other manufacturers also equipped certain models with the D-Jetronic:

  • Mercedes-Benz from October 1968 in the 250 CE of the W114 series as well as 280 E and 280 CE, R / C107 280,350,450 (USA and Europe) SL / C (8-cylinder until 1975, 6-cylinder until 1976), W108 / W109 280 SE 3.5 and 4.5 USA, W109 3.5 and 4.5 USA, W111 Coupe / Cabrio 280 SE 3.5 and W116 280,350,450 SE / L (8-cylinder until 1975, 6-cylinder until 1976)
  • Opel Commodore GS / E 2.5 and 2.8 (from April 1970 to February 1975), Admiral B 2.8 (from March 1969 to July 1976), Diplomat B 2.8 (from March 1969 to February 1975)
  • Citroën DS 21 ie (from October 1969 to August 1972), DS 23 (from September 1972 to July 1975), SM Injection (from May 1972 to July 1975)
  • Volvo P 1800 E (from September 1969 to July 1972), P 1800 ES (from September 1971 to July 1973), 142/144 Grand Luxe (from September 1970 to July 1973) and 164 E (from September 1971 to July 1974)
  • Saab 99 E (from November 1969 to August 1972)
  • Renault R 17 (from October 1971 to August 1973), also in the variants R 17 USA (from June 1972 to July 1974), R 17 Gordini (from September 1973 to June 1977) and Renault Alpine A110 and A310
  • From autumn 1971 BMW delivered the 3.0 Si and 3.0 CSi , and from 1972 also the BMW 3.0 CSL with the D-Jetronic.
  • Lancia 2000 HF Coupé and HF Berlina (from 1972 to 1974)
  • From 1975 to 1980 Jaguar used a modified version of the system in the twelve-cylinder models of the XJ-S and XJ Series II and III . It was manufactured under license by the British manufacturer Lucas and adapted for the requirements of a twelve-cylinder engine.

From 1976, the D-Jetronic disappeared from the current models, as the automobile manufacturers increasingly used the injection systems K-Jetronic and L-Jetronic , which were further developed by Bosch .

function

The principle of the D-Jetronic (initially only called Jetronic) is based on the fact that the fuel requirement depends on the amount ( mass ) of the intake combustion air, which is derived from the air pressure in the engine's intake tract, the temperature and the speed (with the displacement) can be calculated. This means that the amount of air sucked in determines the pressure in the intake air distributor behind the throttle valve : When the throttle valve is closed, little air can be drawn in and the air pressure in the intake air distributor drops. When the throttle valve is open, a lot of air can flow in and the pressure in the intake air manifold increases. This pressure is determined by the intake manifold pressure sensor (also called a pressure sensor) and transferred to the electronic control unit as an electrical signal. On the basis of this and the measured variables engine speed, engine and intake air temperature determined by other sensors , the control unit determines the respective opening times of the injection valves and thus the amount of fuel injected.

The most important sensors is the intake manifold pressure (also pressure sensors or the D-Jetronic MAP sensor of "manifold absolute pressure"), who also gave the system the name: D jerk sensor controlled.

Bosch offered the system for four, six and eight-cylinder engines. The electronic control unit is built using analog technology. The analog computer receives the injection signal from two (4-, 6- and 12-cylinder) or four (8-cylinder) mechanical release contacts, which are located opposite each other in the distributor and are actuated by a cam on the distributor shaft . Each trigger contact switches a group of injection valves, which supply one half or one quarter of the engine's cylinders with fuel per switching pulse from the associated contact. For Jaguar, Lucas developed a contactless trigger electronics and an additional amplifier for the 12 injection valves. Injection takes place in the respective intake manifold; so it is a manifold injection.

The control units of the D-Jetronic consist of two circuit boards , which are constructed and coordinated with discrete components : A main circuit board , which contains components and functions common to all applications, as well as an auxiliary circuit board specially designed for the respective motor, with which the volumetric map for the Engine is implemented. This map depends on the respective engine construction and was determined before the design of the circuit for the secondary board on a dynamometer by measuring runs on the engine.

In addition to the sensors, there are additional control elements. This includes:

  • Acceleration enrichment via 2 contacts in the throttle valve switch
  • Full load enrichment via absolute pressure switch (very early) or full load transition in the pressure sensor or full load contact in the throttle valve switch (late)
  • Cold start enrichment via external electronics with thermal timer and cold start valve

The control map of the injection could only be changed (except when idling with a potentiometer on most control units) by changing electromechanical sensors or changing the wiring of the control unit. So very soon, especially at VW, there were confusing and sometimes contradicting assembly regulations. For these reasons and because of its electronic pioneering role, the D-Jetronic was not particularly popular with the mechanics-oriented workshops of the time. It was impossible for the workshops to diagnose the correct function of intake manifold pressure sensors and control units. Appropriate test devices were only available very late. In addition, parts from any manufacturer were plug-compatible, so that they were often exchanged wildly. A change in the control behavior of the system was actually not possible without changed components. Automobile manufacturers, however, often shied away from the associated costs or confused their authorized workshops with complicated exchange programs.

Early and all Mercedes-Benz versions of the D-Jetronic had a so-called overrun cut-off. This switched off the entire fuel supply in overrun mode, i.e. with the throttle valve closed and engine speed above an engine-specific and temperature-dependent limit speed. It did save fuel, but engines with high mileage tended to smoke blue when overrun, as engine oil that got into the combustion chambers was only burned after the end of overrun when combustion started again. In addition, particularly when switching from overrun fuel cut-off to normal operation, the engine frequently jerked and jerked. For this reason, the overrun cut-off was eliminated from the system by some manufacturers before 1970. For the stricter exhaust gas regulations of the American market, specific controls were often built and additional external thrust boosters introduced: A purely mechanical auxiliary control that was to improve the exhaust gas values ​​in overrun mode entirely bypassing the D-Jetronic and controlled only via vacuum valves.

Further development

The idea of ​​the pressure-controlled injection system as a mixture preparation system was in principle useful. In early years, the systems suffered from stability and a. the fuel pump, the electronic control (e.g. breaking of solder joints due to temperature changes) and their sensors; sufficient reliability had been achieved in later years. With the following systems, K-Jetronic (mechanical) and L-Jetronic (electronic), Bosch abandoned the pressure sensor principle and relied on air volume measurement via a damper. As a result, engine changes during the life of a vehicle, such as wear, combustion chamber deposits and tolerances in the valve setting, can be better recorded and a constant exhaust gas quality can be achieved. The air volume measurement was more precise, and the new systems were also better suited for measures for exhaust gas recirculation. Further development goals of L-Jetronic as a direct successor system to D-Jetronic were to reduce costs and, at the same time, increase reliability. For example, the number of components has been reduced from 300 to 80, in particular through the use of integrated circuits instead of discrete elements. The inadequate flexibility due to the analogue working method also required many variants of the system and the associated problems in spare parts logistics meant that the D-Jetronic was hardly used from the mid-1970s, except for Jaguar.

The Japanese manufacturers, including Mitsubishi , Nissan and Toyota , refined the system after acquiring the patents and eliminated the disadvantages. The control units are built in digital circuit technology with microprocessors and evaluate the signal from a lambda probe for exhaust gas aftertreatment with a vehicle catalytic converter (lambda control). The systems are very reliable and are installed under license in many vehicles in America, for example.

General Motors developed an injection system for the Chevrolet Cosworth Vega EFI with an intake manifold pressure sensor, throttle valve switch, injection valves, pressure regulator and fuel pump from the Bosch D-Jetronic, which was based on the Bendix Electrojector system.

The L-Jetronic was later replaced by the LH-Motronic, which was equipped with a more precise air mass meter. But the D-Jetronic has also been further developed (today, for example, Bosch ME-Motronic), either only equipped with a MAP sensor (e.g. in many Peugeot vehicles) or equipped with both MAP and air mass sensors (in Ford vehicles ). Another variant was manufactured by the Hella company as MPFI (Multi Point Fuel Injection) for Audi and used in the early 2.6 liter V6 engines. These controls also work without an air mass meter and, in addition to the injection control, also take over the electronic ignition control.

Individual evidence

  • Charles O. Probst, Bosch Fuel Injection & Engine Management, Robert Bentley Publishers, ISBN 0-8376-0300-5
  • Hermann Scholl, Electronically Controlled Gasoline Injection, Bosch Techn. Reports 3 - Issue 1 - November 1969

Web links

Individual evidence

  1. ↑ a b c d Walter Kaiser: Bosch and the motor vehicle - review 1950-2003. Hohenheim-Verlag, Stuttgart - Leipzig, ISBN 3-89850-117-5 , pp. 111 .
  2. ↑ D- and L-Jetronic petrol injection 1975 / K-Jetronic mechanical petrol injection 1981 . In: Bosch - Automotive Equipment Division (Ed.): Technical briefing . Stuttgart.