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  View original topic: Bendix "Electrojector", forerunner to Bosch D-Jet
Donnie strickland Wed Mar 23, 2016 10:11 am

By chance, last week I ran across this webpage about the "Electrojector" electronic fuel injection system, developed and built by Bendix Aviation in the 1950's:
http://www.allpar.com/cars/desoto/electrojector.html

I had heard of the Bendix system before, and I knew that Bosch had purchased the rights to the system from Bendix, but I never knew the Bendix system was actually used on production cars. In 1958 it was used on 35 cars built by Chrysler, before the plug was pulled, so to speak. It seems the weak spot was the capacitors in the electronic control unit, capacitor design and construction not yet being reliable enough for automotive use.

Samba members familiar with D-Jet will recognize many of the same elements used in that system --

--Fuel ring, with supply and return lines
--Fuel pressure regulator
--Individual injectors (disc-valve injector design in this system)
--Throttle valve switch
--Electronic cold start and warmup sensor
--Air temp sensor
--And of course, a manifold pressure sensor.

Here's a photo of the inside of the hand-assembled control unit (all photos from allpar.com):


The fuel ring and four injectors. Notice the fuel ring is metal:


Here's the primary throttle body, with its fabric-covered sensor wiring, and the pressure regulator at rear:


And finally a photo from the shop manual, showing the two distributors. One is the regular ignition distributor, the other, mounted at a 90 degree angle to the first, is for the injection trigger points. Bosch was able to integrate these functions into one distributor.


It's interesting to see how, in less than 10 years, Bosch was able to develop this system into the D-Jet used on Type 3 models.

It was really a system ahead of its time, especially since component manufacturing wasn't quite up to snuff yet. But it's interesting to note that even in the Fifties, one of the advantages cited by Bendix's president was that fuel injection "eliminates the 'smog' problem created by unburned fuel exhausted from the engine", which was the reason VW went to fuel injection ten years later.

raygreenwood Wed Mar 23, 2016 10:51 am

Saw that a while back but thanks for posting !

The biggest issues as you note were the electronic component quality. The wires and connectors were notably substandard for anything controlled through resistance.

It was not until 1966 that some of the more reliable silicone and germanium based solder on transistor technology hit the market.
Rapid changes and improvements were made to this circuit technology yearly through the 60s and 70s....which is most probably the main issues as were being discussed in D/A/N's thread ...about more fragility issues with transistors and board traces in the earlier A/B D-jet systems.

Ray

Tram Wed Mar 23, 2016 5:54 pm

I'd read about this setup years ago. Very fun.

raygreenwood Wed Mar 23, 2016 9:38 pm

Tram wrote: I'd read about this setup years ago. Very fun.

About two years ago....."The Pickers".....came across a barn find of one of those 35 cars with the injection and engine complete.....crazy!

Ray

KTPhil Wed Mar 23, 2016 11:18 pm

Fascinating! I read about the patents but have not seen photos of the system in place.

I don't see an MPS in any of the photos. Is that round thing near the distributor for the trigger points?

Donnie strickland Thu Mar 24, 2016 6:58 am

I think that's the vacuum advance for the ignition distributor. I believe the MPS might be mounted in front of the primary throttle body, but that's just a guess. I know there's one somewhere.



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