Dean's Activa/XM/V6 and now Talbot blog

[white exec]

Not seen anything like that before.

[xantia_v6]

I think that you will find that the amplifier module controls the dwell not the timing. There would be no point having mechanical weights and springs moving the timing if the electronics were doing it.

Adjusting the timing for fastest idle is not likely to be correct, as the timing at idle was often designed for best emissions, not best performance.

[Deanxm]

i agree it would just make the system complex for no reason, these mechanisms cannot alter the ignition timing directly, it is impossible. It has to be the ignition module that does it.

There is a coil, an ignition module, a crank sensor and distributor, i guess they stuck with the weight and vac mechanisms as sensors because if not they would of had to change a lot more to provide engine load and speed info, granted they have the crank sensor but maybe it just was part of the natural evolution or the lowest cost stopgap method to achieve what they wanted.

D

[xantia_v6]

If I understand the photographs correctly, the timing is controlled by the arms that go past the trigger coil, the arms are advanced by the centrifugal weight mechanism, so it does adjust the timing. I am guessing (not clear in the photos) that the vacuum module moves the coil assembly relative to the body of the distributor, so that directly adjusts the timing as well.

The timing module does not need a crank sensor signal (and I don't think it has one) because it already has the engine speed by counting the pulses from the trigger coil.

One other reason that I don't think that the amplifier module controls the timing is that it is a non-programmable generic module, but the timing curves will differ considerably depending on the design of each type of engine it is fitted to.

[Deanxm]

yes the timing curve issue is what is worrying me, i found a Replacement module from intermotor but will it do the same job, the one on the van is a Ducellier and is double the size of the usual Bosch units but the ebay listing says its compatible and found the link to the seller on the talbot owners club.

So far as distributor operation, there is a solid shaft that runs right through, drive gear keyway on one end, rotor arm on the top, the centrifugal weights are mounted on this shaft by way of a keyed plate in which they sit, these (when thrown out) rotate a plate above with 4 metal legs which point up and sit around the winding of wire in the top half of the distributor.
The vacuum advance mechanism in the top half of the distributor body operates another almost identical plate which sits above the winding of wire with 4 legs that point down to sit around the winding in the same plane as the ones operating by the weighted centrifuge underneath but offset to give an evenly spaced gap between each leg on each of the two plates, the cap is clipped and keyed to the body of the distributor and does not turn.
The copper winding terminates with two connectors which plug into a lead length terminating with a 3 pin bosch EV1 type plug connected to the loom that splits to the ignition module (6 pin) and the 4 wires that go to the coil low tension side, which is odd as the van has no Tach and was not available as an option.

To be clear as i think the above is unclear, the sensor coil cannot move, the cap cannot move and the rotor arm is fixed to the drive off the camshaft, the only things that move are the two armed plates around the outside of the coil of wire on the white spool.

D

[Deanxm]

Actually..........the timing curve will be dictated by the signal sent by the movement of the mechanical components around the coil.............so the module only has to do what it's told, meaning it does not need to be programmed with the ignition curve and will fit multiple vehicles........... i think.

D

[Deanxm]

also the crank sensor is not plugged into anything, i have just checked and the connector is zip tied to the front of the block...........later gearbox fitted at some point from a vehicle that had fuel injection maybe? not sure this would be my problem though as to control ignition advance you need to have engine load and speed information and a crank sensor cannot see load, must be as you say, taken from the coil type sensor.

D

[white exec]

My guess is that the ign module is just an amplifier, to convert the low-level pulses from the inductive distributor into a suitable input for the h.t. coil. Even older 'electronic ignition' systems could feed the primary side of a coil not with d.c. (such as directly from old-fashioned distributor points) but with a capacitive discharge high-frequency up to 300v p-p. This was harmless to a 12v coil, but operated it much more efficiently than a d.c. input, generating a high-energy spark of longer duration.

[Deanxm]

My guess is that the ign module is just an amplifier, to convert the low-level pulses from the inductive distributor into a suitable input for the h.t. coil. Even older 'electronic ignition' systems could feed the primary side of a coil not with d.c. (such as directly from old-fashioned distributor points) but with a capacitive discharge high-frequency up to 300v p-p. This was harmless to a 12v coil, but operated it much more efficiently than a d.c. input, generating a high-energy spark of longer duration.
> Post edited by white_exec to delete incorrect statement about distributor advance/retard.

I thought they both advance? advance increasing with RPM due to increased piston speed means you need to give the ignition a head start to keep max gas pressure at the same crank angle (piston and bang still meet in the same place) for max power and vac advanced so that on a trailing throttle or small throttle or light loads with a lower charge density where the flame front will be moving slower as a result, piston and bang, again, meet in the same place?

I Know when i had all the trouble with the XM one and i went digging i found out how it worked but each type MTR-01/02/03/04 work differently, but yes i think you are right, however this is the same problem i had before as i say, i always thought the ignition amp either worked or didn't but when i had the bad HT leads it was frying the ignition modules, they would work but i would get a mid-range misfire and then much later intermittent no starts. the way i read it they seem to act like a relay but are obviously solid state and can operate at very high speed, some have a chip in them some just have what look the VN05's??, those drivers that fail after neglecting diodes in a hydractive 2 ecu. either way, i have stripped and cleaned the mechanisms within the distributor, oiled it and managed to put it back together with minimal parts left over so tomorrow i will put it back on the van and set the timing correctly again and see if i can get the ignition to advance when revved, if i can see the ignition timing moving at all which the vac line attached or a change in engine speed i will be happy, if not i will wait for a new module and then if that makes no difference............new distributor? wish i could find the specs for this one so i could find out how to test the coil of wire inside as that is obviously a key component / sensor for ignition timing.

D

[white exec]

Sorry about the wrong statement about action of vac and weights. Have deleted it. You're right: both are there to advance ignition timing.

Am unsure what that large coil of wire actually does. The spark triggering is presumably done (as Mike says) by the metal fingers passing a pick-up sensor, which is usually quite small - like a TDC or ABS sensor. So why the large coil?
If that coil is part of the sensor, then it must be working, or you wouldn't be getting a spark at all.

Does that dizzy have any maker's identification, so we could look for some documentation for it?

[Deanxm]

No worries Chris, for a moment i thought i had misunderstood my latest nerd book, as the wife calls them

mmm, yes it looks like a (giant) home-made abs sensor without a case, it does have a resistance which briefly decreases as either of the mechanisms is moved but always goes straight back to .37ohm as soon as either of them stops moving.

I see what Mike means now, the advance mechanisms control the curve and the module triggers the coil from that signal, so, if the pickup in the distributor is working (as, like you say, it must be as i have a spark) then why will it read the static signal but not when it advances with the metal arms that move around the outside............ the static timing signal must be triggered from the main distributor shaft affecting that coil of wire? but there is nothing on the shaft to affect the coil and send a signal...... Am i missing something here, Mike, you said it knows engine speed from the trigger coil, i take it you are talking about the big coil of wire inside the distributor? is the rotor shaft magnetised on one side do you think, you can see the section of shaft here that passes through the coil in the top section, there is nothing on it that would disrupt the magnetic field from the coil, i take it thats how it works?
IMG_5247 by Deanxm, on Flickr

My distributor is a Ducellier, no other marks, i have read online that many types were fitted and that one of them was the M12 which is not the one i have, the M12 makes sense, it has the magnetic pickup under the rotor arm in place of the points, mine has nothing but air in this location, you can see in the photos on the prev page.

D

[white exec]

It will be the fingers that do the triggering (Hall effect), not the shaft. Presumably the metal fingers rotate, and the coil unit stays stationary, with just one peripheral part of it being the sensing point.
Could the two small bright metal blades (by your thumb in photo#2) be the sensing point which the fingers pass across?

[xantia_v6]

in the picture of the pick-up assembly, there are 4 metal fingers near the periphery, you can see 3 clearly at about 12 oclock, 3 oclock and 6 oclock in the photo. I think that the moving fingers pass these to complete the magnetic circuit and trigger the spark.

You should try to find the advance specs for this engine, some engines have surprisingly little advance if the basic design is not prone to knocking.

[white exec]

Looks like one of these...
https://www.ebay.co.uk/itm/DISTRIBUTOR- ... 1927790940

Some part numbers included in the Important Notice part of the ad.

[CitroJim]

That's very similar to the distributor I had on my old 205GTi... They were shocking for puncturing their vacuum advance capsule diaphragms...

Normally a suck-test could determine but not always... Can you see the mechanism move when you suck on the vacuum pipe Dean?