• Feb 6, 2007
Every car on the road now has fuel injection. There was no real battle royale between electronic systems and mechanical, though both flavors saw plenty of development. Rochester's Ramjet system was effective and quite slick, contained in a special intake manifold. Bosch had K-Jetronic which was a mechanically metered system that later gained some feedback electronics, becoming the very first FI system to utilize an exhaust gas oxygen sensor for fine mixture control. Fuel injection systems have now gone the way of all-encompassing powertrain management setups, controlling ignition and fuel; as well as talking to the transmission, anti-lock braking system and stability control. Electronic systems all owe something to the first successful electronic fuel injection rig to be mass-produced: Bosch D-Jetronic. DJet, in turn, has its own piper to pay.

More after the jump

Ramjet-Injected 283 The Chevy small-block made a big splash in '57 when it first came equipped with a Rochester injection system that allowed the 283 to growl out 1 horsepower per cubic inch. Prior to that, the Mercedes 300SL debuted an FI system in 1954. The Volkswagen Squareback's engine was as important as both of those mechanical systems, it not even more momentous in its own right. The "suitcase" iteration of VW's ubiquitous flat-four located under the rear cargo area was fitted with electronic fuel injection beginning in 1967. Metering hydrocarbons to the 1600cc air-cooled wonder was the first electronic fuel injection system suited for mass production, Bosch D-Jetronic. There was a system that preceded D-Jet. In fact, D-Jetronic traces its lineage directly back to the first short-lived and disastrous attempt at electronic fuel injection, ten years prior. The funny thing is, D-Jet was mainly the same system built with better parts; kind of like the IMSAI was an Altair that worked.

The D-Jetronic system was based on licensed patents and designs from Bendix. Bendix was a behemoth company that made everything from brake parts to avionics to radios and televisions, even computers. In the 1950s, Bendix had the talent and the expertise to devise a system that would be less mechanically complex through the magic of electronics. The Bendix system was initially for aircraft use, but the company put their propeller-heads to work on it and came up with a system that worked for the constantly varying throttle positions of an automobile.



EFI harnessed the newly affordable power of electronics. The Bendix engineers figured out that they needed to measure the pressure in the intake manifold and have the electronics perform some calculations against the constants (engine pumping losses, cylinder volume, fuel pressure), while also taking in to account a few other variables such as engine temperature and of course, throttle position. Sounds pretty much like a modern FI system, doesn't it? The microprocessor had yet to appear on the scene, and transistors were still expensive in the late '50s when the Bendix system came to market. It sounds novel to us now, but injector pulse duration and timing were controlled by a seperate set of points in the distributor. Ignitions would still be using points for many years, so an extra set for the FI was simply the only way to get the job done, and an elegant solution at that.



The Bendix system was fitted to a very small number of Chrysler products beginning in 1957. It was an expensive option that didn't last very long. The price was only half the reason for failure. The build quality of the system wasn't up to the task of being reliable in the automotive environment. While the basic design was sound, costs were cut where possible to bring the price down from astronomical to ridiculous. Even in the much cooler underhood environment of 1950s cars, the EFI systems failed at a fast clip. It did work, however, and Bosch saw the inherent promise.

In the decade between the Bendix "Electrojector" and Bosch debuting D-Jetronic, the cost of the electronic bits had dropped. Bosch also did a lot of work refining the design. It still used an manifold pressure sensor and triggered the injectors with their own set of points hidden in the base of the distributor. Bosch continued development on the system, adapting it to many different engines from Cosworth Vegas to Porsche 914s. Subsequent systems would be even better refined, using variable fuel pressure, controlling the pulse width and timing with microprocessors and integrating ignition functions and self-diagnostics. They generated many patents in the process and became quite adept at electronic engine management. So, while D-Jet is the granddaddy of EFI systems, it owes its existance to great-granddaddy Electrojector.

Excellent reference materials at Allpar and Rennlist were immensely helpful, as were many hours under the arse of a '69 Squareback.


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    • 1 Second Ago
  • 4 Comments
      • 7 Years Ago
      The words "Bosch K-Jetronic" evoke, for me at least, reactions similar to Moe Howard's when he hears the words, "Niagara Falls". At least Niagara was running -- that's more than I can say for the several VWs my family owned that were "blessed" with this Rube Goldberg contraption. I'm sure there are many happy-ever-after stories out there, but mine isn't one of 'em.
      • 7 Years Ago
      The 1957 Rambler Rebel was slated to become the first EFI production car, until problems with the Bendix EFI system forced the Rebel to use a carburetor instead. It looks like the car in the latter few pictures is Don White's - the only remaining 1958 De Soto to still have its EFI system intact.
      • 7 Years Ago
      Very cool write-up, I love this sort of forgotten history.
      • 7 Years Ago
      Nice writeup!

      BTW: The mechanical FI system in the 300sl was smooth and quiet at low speeds, but a terrifyingly noisy thing above 4000 RPM.

      Have a listen:
      http://chuck.goolsbee.org/archives/9

      (yes, I have had the privilege of driving one... it was an amazing machine. Light years ahead of anything else of the era!)

      --chuck