Distributor Less Ignition retroFit?

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Tim Leech
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Distributor Less Ignition retroFit?

Post by Tim Leech »

My 19TZI has normal electronic ignition with dizzy cap etc

I have noted a few other cars slightly later have distributor less ignition?

Is this plug and play,

My 1.8i 8V xantia has it also
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Re: Distributor Less Ignition retroFit?

Post by Jaba »

Tim Leech wrote:
Sat Jun 08, 2019 11:04 am
My 19TZI has normal electronic ignition with dizzy cap etc

I have noted a few other cars slightly later have distributor less ignition?

Is this plug and play,

My 1.8i 8V xantia has it also


I am not sure Tim. If your ECU has a TDC sensor which sends a signal to the ignition amp and varies the timing according to the load then yes it can be done by swapping the HT coil pack for the dizzy.
Otherwise you will need the full conversion of ECU, loom and the rest to do a full 1.3 conversion from a donor with a CAT fitted (I think your TZi has a cat). In other words it is not worth the trouble for the small mileage your TZi does.
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Re: Distributor Less Ignition retroFit?

Post by Kaapelimies »

I'm quite sure it's not just about the TDC-sensor, as then the spark would come in all 4 cylinders at the same time and it wouldn't work very nice in the cylinder that is sucking in the fuel mixture.. You need the ecu and the wiring loom (and to have all components attached) also, which are quite an easy fit as they are all separated from other electricity in a BX. It's an easy weekend job.
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Re: Distributor Less Ignition retroFit?

Post by Tim Leech »

Ahh ok I will leave as is!
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Re: Distributor Less Ignition retroFit?

Post by Way2go »

Kaapelimies wrote:
Mon Jun 10, 2019 3:46 pm
I'm quite sure it's not just about the TDC-sensor, as then the spark would come in all 4 cylinders at the same time and it wouldn't work very nice in the cylinder that is sucking in the fuel mixture.. You need the ecu and the wiring loom (and to have all components attached) also, which are quite an easy fit as they are all separated from other electricity in a BX. It's an easy weekend job.


The system (or principle) is actually know as "Wasted Spark" which if you think about it does not conflict with the induction stroke as that is paired with a power stroke for which the spark has occurred just before TDC (ignition advance).

However this system, the Motronic 3.1 used on the later GTi 8v does not use a vane air meter to calculate fuel demand but the more advanced MAP sensor (Manifold Absolute Pressure). There is usually no cat involved for uk BXs except for possibly their last number off the line.

Clearly the BXs used different ECUs or at least different firmware within them to support the various types of Motronic (or the earlier Jetronic) ignition and injector systems.

I guess it is questionable on the perceived worth of doing the upgrade but the MAP sensor does give a better driving sensation as acceleration is immediate and more powerful being without the lag associated with the mechanical air meter. With improved spark efficiency too I feel that Motronic 3.1 gives a great performance advantage and was a positive upgrade by the Citroen Designers. :D
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Re: Distributor Less Ignition retroFit?

Post by Jaba »

I wonder why it wasn't used on the 16Vs.
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Re: Distributor Less Ignition retroFit?

Post by Kitch »

Motronic 3.1 is the system used on the 16v, along with 1.3 and 4.1 (one is two-row, one is three-row (with a knock sensor), and the other is for the catalysed cars with lambdas).

I could be wrong, but I'm pretty sure the GTi used something different. I know the majority were L-Jet, though I imagine it must have had Motronic os some type to run wasted spark.

The 16v is actually distributorless too - there is a rotor arm and dizzy cap, but they run directly off the inlet camshaft. The arm has a wide blade, so the ECU can time exactly when the amplifier is triggered. All the spark timing and fuel delivery mapping are driven by the ECU; the cap just sends it off to the various plugs, managing not to 'waste' any in the process! :lol:
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Re: Distributor Less Ignition retroFit?

Post by deltic »

See this thread for an image of the distributor less Motronic MP3.1 ignition system a GTi: https://www.bxclub.co.uk/forum/viewtopi ... =2&t=22438
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Re: Distributor Less Ignition retroFit?

Post by Jaba »

Kitch wrote:
Thu Jun 27, 2019 9:59 am
Motronic 3.1 is the system used on the 16v, along with 1.3 and 4.1 (one is two-row, one is three-row (with a knock sensor), and the other is for the catalysed cars with lambdas).

I could be wrong, but I'm pretty sure the GTi used something different. I know the majority were L-Jet, though I imagine it must have had Motronic os some type to run wasted spark.

The 16v is actually distributorless too - there is a rotor arm and dizzy cap, but they run directly off the inlet camshaft. The arm has a wide blade, so the ECU can time exactly when the amplifier is triggered. All the spark timing and fuel delivery mapping are driven by the ECU; the cap just sends it off to the various plugs, managing not to 'waste' any in the process! :lol:


The early GTi used the 1.3 system with the dreaded flowmeter and no TDC flywheel sensor as did all the TZIs. Then 1990 onwards the much better distributorless 3.1.
Now I could be wrong but I call a system with a dizzy cap and rotor arm a distributor based system i.e all 16Vs, no matter how the spark is timed. Dizzy caps and rotors will all ultimately fail so the 3.1 system is a definite step forward.
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Re: Distributor Less Ignition retroFit?

Post by Kitch »

Jaba wrote:
Sat Jun 29, 2019 10:27 am
Kitch wrote:
Thu Jun 27, 2019 9:59 am
Motronic 3.1 is the system used on the 16v, along with 1.3 and 4.1 (one is two-row, one is three-row (with a knock sensor), and the other is for the catalysed cars with lambdas).

I could be wrong, but I'm pretty sure the GTi used something different. I know the majority were L-Jet, though I imagine it must have had Motronic os some type to run wasted spark.

The 16v is actually distributorless too - there is a rotor arm and dizzy cap, but they run directly off the inlet camshaft. The arm has a wide blade, so the ECU can time exactly when the amplifier is triggered. All the spark timing and fuel delivery mapping are driven by the ECU; the cap just sends it off to the various plugs, managing not to 'waste' any in the process! :lol:


Now I could be wrong but I call a system with a dizzy cap and rotor arm a distributor based system i.e all 16Vs, no matter how the spark is timed. Dizzy caps and rotors will all ultimately fail so the 3.1 system is a definite step forward.


I'd say you're wrong :lol:

Distributor is the unit that advances/retards the ign. timing, as well as triggering the ignition amplifier. On a distributorless system, this is all controlled by the ECU. The fact it has a cap and arm is irrelevant. It's just not a wasted spark type, that's all.

I have got muddled myself, however - 16v didn't use M 3.1 at all. The 2-row cars are ML4.1, and the later cars (91 on) used M1.3, with a 3-row ECU, knock sensor and provisions for a cat.

The bit I'm confused over is the earlier GTi 8v, as I could have sworn they were L-Jet. Certainly possible for me to be wrong on this, as I've not spent much time around GTis. I knew the later dizzyless cars were Motronic.
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Re: Distributor Less Ignition retroFit?

Post by rutter123 »

My H plate was Jetdonic
I seem to remember my old mk1 golf gti having a very similar system,
Seems most J & K plated use the Motronic, which in my opinion is the better system
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Re: Distributor Less Ignition retroFit?

Post by Jaba »

Kitch wrote:
Mon Jul 01, 2019 2:11 pm

I'd say you're wrong :lol:


Well one of us is - but who cares?????!!!! Its just semantics.
You will have to stop calling the 16Vs cap and rotor for the HT leads the distributor cap now since it isn't one [-X
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Re: Distributor Less Ignition retroFit?

Post by Kitch »

Nah, I don't think I will.
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