DLS ignition unit musings

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251906083A, manufactred by Telefunken (TLF) or Siemens or AEG. Marked 4-zyl.

I've been thinking a bit about this box of mysteries and what it actually does in a VAG TCI application when used with a double sided advance/retard DJ type distributor, since my wbx6 has provision for one but I don't have one specifically for a 6- cylinder and I don't know if thats even a problem.

Curiously, the Audi 100 A6 C4 variant of the same part 035906083 is not marked 4-zyl but does carry the marking "impedanzwandler" which translates as "buffer amplifier"

So it may not be any kind of early digital advance/retard module after all, but something that transforms the impedance of the incoming signal for some purpose.

Thoughts?

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However, I have gone down the rabbit hole and found a samba topic (#735600, page 4, oscilloscope waveforms of fuel pump, hall sensor, injector, spar) where someone has tested the DLS and it does definitely advance the timing slightly if the engine idle rpm are pulled down by external factors. So its a sort of anti-stall device but is inactive above 940 rpm.
Crucially it also appears to smooth/reduce the amplitude of the signal from the hall trigger which then goes to the ignition amplifier aka TCI unit.
So is it possible that running an engine without a DLS can lead to premature TCI failue?

[cobblers]

Ayup Ian! seen your email.
It's my understanding that this just tweaks the ignition timing to help with the idle. Below the target RPM it'll advance the timing a bit, just to try and add a small amount of "closed loop" to the system for a more stable idle. That way you can live with a little bit less air bleed and it'll stop the RPM creeping up so high when the engine is warm.

As part of it's operation it will buffer and clean up the signal coming from the hall sensor, but AFAIK the bosch ignition units were originally designed to be happy to run directly from a hall sender anyway. I don't think running bypassed is likely to damage anything, if it runs then it'll probably be fine.

To get any idle improvement, you'll need a 6 cylinder one (tuned with a 50% lower setpoint if measured in Hz, if you use a 4 cylinder one, at 800 RPM it'll think the engine is doing 1200rpm so it'll have no effect until the engine has already cut out)

A 4 cylinder one on a 6 cylinder engine will just essentially work as a signal conditioner so there's no harm in it being there.

It might be possible to modify a 4 cylinder one and change whatever it uses as a time reference. If it's a crystal then it's straightforward. RC circuit needs a bit more beard twiddling.

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I've seen a pic of whats inside the unit and there's four seprate ICs so its busy thing. For my needs, I'd have to track down something suitable that was using 6 banger using L-jetronic circa 1985.
VAG were still getting into their inline 5's for everything apart from the V8 so I've got to go off brand.
Jaguar had Lucas Opus and the 3CU ecu iirc.
Volvo 265? What else was there?

[Robsey]

Probably some of the big Vauxhall Opels

Opel Monza
Opel Rekord
Vauxhall / Opel Senator
Vauxhall Carlton / Opel Omega-A

I think they dipped into 6-pot K Jetronic and L Jetronic

Even the later Mk2 Cavalier 18SE (SRi 130) ran on one of the flavours of Jetronic. 1985 to 1988 I think. (4 pot only)

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Thats a thought. However Vauxhall Opel of the era isnt my dept! K-jet is constant spray injection so thats a different animal, it would have to be L-jetronic with solenoid injectors and some form of Hall trigger/TCI ignition (which is more important) and use the AMP 3-pin round plugs.

[Robsey]

I will see what I can find out for you...

The only thing I am questioning is the AMP 3-pin round plugs...
The rest sounds like standard early Bosch injection components on the 80s Vauxhalls and Opels

Carlton 30NE used an LE2 and LU Jetronic System
Same for Senator.

I can only assume the Cavalier and Astra 4 pot units (18E) were the early L Jetronic
Cavalier with 18SE and 20SE / 20SEH were early Motronic units.

I can't find info on the early Opel Monza