914 1.7 FI Question, Accel Enrichment injector operation Options

[nordfisch]

...

From brads djet site,
Also sends a signal at wide-open-throttle, but this signal is not used by the ECU for full-load enrichment, which is handled by the Manifold Pressure Sensor.

Don't forget Brad owns a 2.0
This car uses a diffent type of TPS (adapted from late VW Type III).
Its TPS is equipped with the full-load contact the late VW type III uses instead of the full-load enrichment by MPS.

This TPS has 5 contacts instead of four - one added for the full load switch (sleeve contact).
Only 4 of these contacts are used <and wired> in the application at the 914 2.0 and the VW Type IV equipped with almost the same engine.

You could use this 5-poled TPS on the 1.7-engines, too. The 4-poled plug has to be plugged in towards one side - it works like the 4-poled TPS then.

Regards
Norbert

--- There are not many types of D-Jet-cars with 5-poled TPS: Mercedes 2.8 + 4.5; SAAB 99 (newer only); Opel Admiral, Commodore, Diplomat (newer only); VW type III from mid 1972 on. ---

[Dave_Darling]

Two of the pairs fire behind open valves and two of the pairs fire behind closed valves.
Don't know why, reducing the wiring?

Reduced the electronic circuitry required to drive the injectors. Remember, in the 60s when this was designed, that stuff was expensive!! (Relatively speaking.) It was cheaper and easier to batch-fire the injectors than to trigger them individually. Plus if you're firing half the injectors at a time, you can use the same basic parts on four, six, and eight-cylinder engines. And they were used on fours and sixes (from various automakers). Not sure about eights.

I think that the TPS-triggered enrichment pulses do pay attention to the position of the trigger points, but I am not at all certain about that.

--DD

[Spoke]

Two of the pairs fire behind open valves and two of the pairs fire behind closed valves.
Don't know why, reducing the wiring?
Mike

CIS systems run the fuel injectors 100% of the time, valves open or closed.

[nordfisch]

- deleted, double post -

[nordfisch]

Hi,
the D-Jetronic-system was used on 4, 6, 8 and 12-cylinder engines. The Jaguar V12 5.3 V12 used a Bosch system slightly converted by Lucas, mostly relabeled components produced by Bosch.


Bosch labeled car brands: BMW (6); Citroen (4, plus SM 6); Lancia (4): Mercedes (6 / 8); Opel (6); Renault (4); Saab (4); Volvo (4 /6); VW / Porsche (4)

4-and 6-cylinders have 2 injection groups - 4-cylinders have 2 cylinders paired, 6-cylinders have 3 cylinders paired (2 groups)
The VW (Porsche) trigger points sets are unique, all other 4- and 6-cylinders have other sets, but all of these are compatible except the Citroen SM.

Mercedes V8 has 4 injection groups, driven by a trigger-points-set with 4 separate points.

The Jaguar V12 has only 2 injection-groups. 6 cylinders inject same time.

There are more cars using a similar D-Jetronic-system licensed by Bendix or Bosch. US-cars, Japanese...

D-Jetronic means "Druck-Jetronic", "pressure-Jetronic", firstly realized in the 50s by Bendix in an American car, read more: https://oldtimer.tips/en/d-jetronic/history

Regards
Norbert

[dknechtly]

Be sure all your grounds are good. Also check that the FI trigger points have near zero resistance. Clean them with a note card, not a file or emory board. A jeweler's cloth is also good.