Bosc Injection System 1951 - 1993 focusing on Jetronic family

1951 Bosch began t build Mechanical Fuel Injection systems (MFI) for Gutbrod Superior 600 and Goliath GP 700. These injection pumps became famous in Mercedes-Benz 300 SL Gullwing rallye cars. But in general they kept limited to luxury cars and Diesel engines while normal engines used carburetors.

Market changed in 1967 with Bosch's first electronic fuel injection system Jetronic for mass production. It layed foundation to a generation of fuel injection systems up today. D-Jetronic was quickly followed by L-Jetronic and mechanical K-Jetronic. In 1979 engine and ignition control were logically combined into Motronic. Following I will tell the story of Jetronic family from 1967 to 1993. It is more widespread than I had thought. I still miss some information like first cars with a secific injection system or details to LH-Motonic and KE-Motronic. I would appreciate your contribution in case you can fill that gap or comment on errors.

It is astonishing that Bosch allowed such a competition in house and maybe even supported it. But it shows that this internal competition was exactly the drive that lead both fractions in Bosch to peak performances. Which fractions do I talk of? Intermittent versus continuous injection? No it is all about mechanic versus electronics!

After successful development of mechanical fuel injection pumps - no matter whether vacuum controlled or enforced control - Bosch had a cash cow they could milk both in luxury fuel and in all Diesel cars and trucks. When electronics made its first steps into automobiles it was already clear that fuel injection pumps would not be sufficient for coming exhaust regulations in the US. That is why electronics made its first try as inJEction elecTRONIC. And boom a star was born that made the brand Jetronic famous. This electronics also replaced carburetors as for example in Volkswagen 1600 E for US market when it was introduced in 1967 as first Jetronic equipped car. Not just deliberately as carburetors would not have been accepted in US exhaust gas regulations.

Of course that was a heavy set-back for success owning mechanicss in Bosch and so they thought of a come-back. Already in 1973 they introduced K-Jetronic to the market. From this time on Jetronic was renamed D-Jetronic so that it could be differentiated. Well between us, K-Jetronic seems the wrong name for a purely mechanical fuel injection system (if we neglect fuel pump for a moment). But Jetronic had become such a reknwn brand that Bosch decided to use it even for K-Jetronic that was later named KA-Jetronic to differentiate from KE-Jetronic. K-Jetronic became possible due to CNC controlled machining tools that could precisely form a metal block into a fuel distributor.

At the same time the electronics successor of Jetronic with the brand L-Jetronic was introduced to the market. But K-Jetronic was so much more successful in market that it looked for long as if mechanical injection systems would take the market back from electronics. L-Jetronic only slowly found its way to market mainly in OEMs like BMW, Opel and Fiat. THe big ones like Mercedes-Benz and Volvo switched completely back to K-Jetronic mechanics. Volkswagen group used both systems.

So victory of mechanical systems over electronics with their child diseases? Well of course we know better. Today all systems are electronics. Electronics returend forcefully back with BMW 633 CSi as integrated engine and ignition control system named Motronic. Continuously more demanding exhaust control and better performance demands also helped electronics. Mechanical KA-Jetronic became an electronic add-on and was then branded KE-Jetronic. But this control was not intrinsic. Mechanical fuel distributors stayed as main principle and they could not fulfill demands in mid 90s anymore. So in the end electronics won the battle they had fought for 25 years in Bosch internally and K-Jetronic was left as a dead end of history.

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Disclaimer: Jetronic, D-Jetronic, L*-Jetronic, K*-Jetronic, Mono-Jetronic und Motronic sind eingetragene Warenzeichen der Robert Bosch GmbH.