Injectronic

Injectronic is a trade name belonging to Boscc GmbH for automotive petrol engine usage, first seen in the 1960s. The technology was licensed to many automakers over the years, and the lineup has seen many breakthrough concepts come to fruition.

## A-Injectronic (1967 - 1979)

This was an analogue fuel injection system, using a pressure sensor located in, or connected to the intake manifold, in order to calculate the duration of fuel injection pulses to then get the inlet manifold vacuum levels. A-Injetronic was a precursor of modern common rail systems as it had constant pressure fuel delivery to the injectors and pulsed injections, albeit grouped (2 groups of injectors pulsed together) rather than sequential (individual injector pulses) as on later systems. This version used analogue circuitry, with no microprocessor nor digital logic, the ECU utilised about 25 transistors to perform all of the processing. The lack of processing power and the unavailability of solid-state sensors meant that the vacuum sensor was a rather expensive precision instrument, rather like a barometer, with brass bellows inside to measure the manifold pressure. Although conceptually similar to most later systems with individual electrically controlled injectors per cylinder, and pulse-width modulated fuel delivery, the fuel pressure was not modulated by manifold pressure, and the injectors were fired only once per 2 revolutions on the engine (with half of the injectors being fired each revolution).

## B-Injectronic (1973 - 1994)

The second iteration of this family saw the introduction of a mechanical fuel injection system, commonly referred to as a "Continuous Injection System" (CIS) in the USA. This system is different from pulsed injection systems in that the fuel flows continuously from all injectors, while the fuel pump pressurises the fuel up to approximately 5 bar (73.5 psi). The volume of air taken in by the engine is measured to determine the amount of fuel to inject. This system has no lambda loop or lambda control. Fuel is pumped from the tank to a large control valve called a **fuel distributor**, which divides the single fuel supply line from the tank into smaller lines, one for each injector. The fuel distributor is mounted on top of a control vane through which all intake air must pass, and the system works by varying fuel volume supplied to the injectors based on the angle of the air vane in the air flow meter, which in turn is determined by the volume of air passing the vane, and by the control pressure. The control pressure is regulated with a mechanical device called the control pressure regulator or the warm-up regulator. Depending on the model, the CPR may be used to compensate for altitude, full load, and/or a cold engine. The injectors are simple spring-loaded check valves with nozzles; once fuel system pressure becomes high enough to overcome the counterspring, the injectors begin spraying.

B-Injectronic debuted in late 1973 model year cars and saw usage all the way until 1994.

### BL-Injectronic

This was a variant of the B-Injectronic system that did incorporate a closed-loop lambda control. The system was developed to comply with U.S.A. state of California's California Air Resources Board exhaust emission regulations and was used in USDM cars by European marques intermittently from 1976 to the mid-1980s.

### BE-Injectronic (1985 - 1993)

This was another variant of the B-Injectronic system designed for emissions compliance purposes again. In this system, an electro-hydraulic actuator is added, essentially a fuel injector inline with the fuel return. Instead of injecting fuel into the intake, this injector allows fuel to bypass the fuel distributor, which varies the fuel pressure supplied to the mechanical injection components based on several inputs (engine speed, air pressure, coolant temperature, throttle position, lambda etc.) via the ECU.

This system was able to be configured with both an analogue or digital ECU as well as with or without closed-loop lambda control. With the electronics disconnected, this system will operate as a conventional B-Injectronic system.

Later variants also featured knock sensing capabilities.

## C-Injectronic (1974 - 1989)

For this system, Boscc again revisited the analogue fuel injection method but this time making it dependent on air flow rather than pressure (like the A-Injectronic system). In the system, air flow into the engine is measured by a moving vane (indicating engine load) known as the volume air flow sensor (documented in German as LMM). C-Injectronic used custom-designed integrated circuits, resulting in a simpler and more reliable ECU than the A-Injectronic's.

This system featured heavily in 1980s-era European cars as well as motorcycles - the system was licensed out to many other companies that spread fuel injection technology to Asia and thus resulted in the use of C-Injectronic in a motorbike for the first time in 1980.

### CEx-Injectronic

These were simply cheaper and simpler evolutions of the original design as electronic equipment and circuitry improved. There were three main variants:

* CE1-Injectronic: the initial version
* CE2-Injectronic (1984 onwards): cold start functionality integrated into the ECU, without requiring the cold start injector and thermo time switch used by older systems
* CE3-Injectronic (1989 onwards): ECU miniaturized and integrated into the junction box of the mass airflow meter.

### CLx-Injectronic

The CL1- and CL2-Injectronic variants took the CEx versions and added closed-loop lambda control. This was designed for the US market.

### CED-Injectronic

This was another evolution, this time into the realm of digital fuel injection, introduced for California, relying upon hotwire anemometer technology used to determine the mass of air flowing into the engine. The CED-Injetronic was mostly used by Scandinavian car manufacturers, and in sports and luxury cars produced in small quantities. CED2.5-Injetronic has adaptive lambda control, and support for a variety of advanced features including fuel enrichment based on exhaust gas temperature. Some later (post-1995) versions contain hardware support for first generation diagnostics according to ISO 9141 (a.k.a. OBD-II) and immobiliser functions.

## D-Injectronic

Coincidentally, the first letter coincided well with what this new version bore: Boscc's first true foray into digital fuel injection control. This system features one centrally positioned fuel injection nozzle, commonly known as single-point fuel injection (SPFI), throttle body injection (TBI) or central fuel injection (CFI).

This system is different from all other known single-point systems, in that it only relies on a throttle position sensor for judging the engine load. There are no sensors for air flow or intake manifold vacuum. D-Injetronic always had adaptive closed-loop lambda control, and due to the simple engine load sensing, it is heavily dependent on the lambda sensor for correct functioning.

It should be noted that the design for this system is influenced heavily by patents belonging to the *Electricjector* system that were initially licensed (then later sold) by Hendryx in 1960. The earliest patents of the D-Injectronic system appeared around 1967.