Most F.I systems are based on the Bosch designs briefly described in the following from Wiki. Some older systems have significant advantages over newer sytems. Read and Discuss.
Jetronic is a trade name for a type of fuel injection technology marketed by Bosch from the 1960's forward. Bosch licensed the concept to many automobile manufacturers. There are several variations of the technology, which represent technological refinements as time passed.
D Jetronic (1967-1976)- analog electronic fuel injection, a vacuum controlled system where the depression (vacuum) in the intake manifold is measured by a pressure sensor and used for calculating the injection time. From the beginning, this system was just called Jetronic; the name D-Jetronic was later used to distinguish it from the newer systems. D stands for Druck in German, which means pressure. 1973 was the last model year when D-Jetronic was in regular use on 4-cylinder engines. By 1974, most vehicle manufacturers changed to K-Jetronic or L-Jetronic. On 6- and 8-cylinder engines, D-Jetronic was used a few years further.
K Jetronic (1974 - ca 1988)- Mechanical fuel injection system. K stands for Kontinuierlich, i. e. continuous. Different from all other systems in that the fuel flows continuously from all injectors and the air that is taken in is weighted to determine the amount of fuel to inject while the petrol pump pressures the fuel up to approximately 5 bar. Commonly called "CIS" (Continuous Injection System) in the USA.
K-lambda Jetronic A variant of K-Jetronic with closed-loop lambda control. Was developed to comply with Californian exhaust emission regulations, and later replaced by KE-Jetronic.
KE Jetronic (Circa 1985 - 1993) Electronically controlled mechanical fuel injection. The ECU may be either analog or digital, and the system may or may not have closed-loop lambda control. Commonly known as "CIS-E" in the USA. The later KE3 (CIS-E III) variant features a knock sensing ignition system.
L Jetronic (1974 - ca 1985) - analog electronic fuel injection. Uses a flapper-type AFM, or Air Flow Meter, to measure airflow into engine. It had a much simpler and more reliable ECU than D-Jetronic, due to use of custom-designed integrated circuits. This type of air flow meter is called LMM, LuftMassenMesser, in all Bosch documentation. It was used heavily in 1980's-era European cars [1]. Similar systems have been built under license by Lucas, Hitachi Automotive Products, Nippondenso, and other companies; though their key components look similar to L-Jetronic parts, those systems should not be called L-Jetronic and parts are usually not compatible. The meaning of the letter L is disputed, either it stands just for Luft - air, or it might be just because it is the letter after K in the alphabet, and L-Jetronic came immediately after K-Jetronic.
LE-Jetronic (1981 - ca 1991) - a simplified and more modern variant of L-Jetronic. The ECU is much cheaper in production as it is built with more modern components and is more standardized than the L-Jetronic ECUs. The connections between AFM and ECU are simplified. Three variants of LE-Jetronic exist: LE1, the initial one. LE2, from about 1984 on, it has cold start functionality integrated in the ECU and does not need the cold start injector and thermo time switch which was used by older systems. LE3, from about 1989 on, miniaturized ECU with hybrid technology, integrated in the junction box of the AFM. LE Jetronic never has closed-loop lambda control.
LU-Jetronic (ca 1983 - ca 1991), the same as LE2-Jetronic but with closed-loop lambda control. Initially designed for the US market.
LH Jetronic (ca 1983 - ca 1998) - digital electronic fuel injection, LH stands for Luftmasse-Hitzdraht - the hotwire anemometer used to judge airmass into the engine. This AFM is called HLM2 (Hitzdraht-LuftMassenmesser 2) by Bosch. The LH-Jetronic is mostly used by Scandinavian car manufacturers and by sports- and luxury cars produced in small series. The most common variants are LH 2.2, which uses an Intel 8049 (MCS-48) microcontroller and usually a 4 kB program memory, and LH 2.4, which uses a Siemens 80535 microcontroller (a variant of Intel's 8051/MCS-51 architecture) and 16 or 32 kB program memory. The LH 2.4 has adaptive lambda control and hardware support for advanced diagnostics according to ISO 9141 but it is questionable whether the software ever got this kind of diagnostics support.
Mono-Jetronic (ca 1988 - ca 1995) - digital electronic fuel injection with one centrally positioned nozzle. In the US, this kind of single-point injection is often called either TBI by GM or CFI by Ford. In France this type is known as Monopoint. Mono-Jetronic 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. Mono-Jetronic always has adaptive closed-loop lambda control, and due to the simple engine load sensing, it is heavily dependent on the lambda sensor for correct functioning. The ECU uses an Intel 8051 microcontroller and usually 16 kB of program memory. Usually no advanced diagnostics.