Ignition Timing

[Roger GrixParticipant]

Hi to all,

Can someone please clarify the details of setting the ignition timing on a Perfo engine?

From the manual, it would appear that the initial, static timing is set at 8 deg. before TDC, using the pin in the flywheel. A further 4 deg of advance is then added using the setting tool. This reads in crankshaft degrees so the distributor body is actually turned 2 deg anti-clockwise.

This gives a static timing of 12 deg before TDC. Now, with the engine running, the centrifugal advance mechanism gives a further 12 deg. of distributor movement (24 deg of crankshaft movement) at something over 3000 rpm. This brings the total dynamic advance to 36 deg before TDC.

In addition to this, the vacuum unit has a movement of 6mm which, according to the graph in the workshop manual, equates to between 17 and 21 deg (crankshaft) at 300 mm Hg.

This would bring the total advance running at about 3000 rpm on a small throttle opening (max vacuum) to in the region of 55 deg .

Am I correct so far?

Now to the added complication of the manual advance and retard mechanism. Where should this be while all of this is going on; Full Advance, Full Retard or in the middle?

I would guess in the middle to allow fine tuning of the other bits.

I suppose that this really amounts to setting the static timing at 12 deg and assuming that everything else is going to work as planned or the use of a strobe light, but I am not sure what you could shine it on.

Regards,

Roger

I Tried to attach a copy of the timing curves from the manual but failed. I tried as .pdf and .jpg . file is just over 1MB so don’t know why it won’t upload

[David FaulknerParticipant]

Manual advance retard set in the middle Roger.

Simple way, get no 1 to TDC and insert the 6mm pin, while it’s locked, put a white line across the cam shaft extension and onto the pulley, then you can use that mark for a strobe light.

However with the flywheel locked, turn the dizzy until the points are on the point of opening, lock everything down, REMOVE the pin from the flywheel and start the engine and it should run as long as you have it locked on no 1 at TDC as you could be locked on no 4

It might need a bit of manual tweaking but it doesn’t need to be 100% accurate to run fine

Simpler with an electronic 123 as you do the above, but turn the dizzy until the led lights up and that’s it

[BernieParticipant]

The book method is fine for a system that is in tip-top condition.  However, in my experience, unless the distributor is reconditioned (or new) wear and tear will inevitably affect the accuracy, no matter how methodical and careful one is.

My method, is basically as Davey suggests ….

• Ensure point gap is correct.  (I  prefer to set the points gap using the dwell angle, rather than with feelers.  On my perfo I had an RB distributor without a vacuum advance and found 54 degrees to be optimum setting).
• With the advance/retard control in the central position use the 6mm pin to locate the initial firing point
• Rotate the distributor clockwise beyond the firing position (points closed) and then turn it back anti-clockwise until the points are just opening, using a timing lamp or meter.
• Clamp the distributior lightly and REMOVE THE PIN
• Start the engine and then adjust the distributor position to give the ideal running position.  This will entail initially obtaining a smooth tick-over and then blipping the throttle to ensure it picks up smoothly.  Tuning “by ear” may sound a bit hit and miss but, after a few goes it soon becomes clear what to expect and how to achieve it.
• Lock the distributor.
• Have a cup of tea.

B………………

 

 

 

[Roger GrixParticipant]

Thanks David and Bernie,
I think that I am becoming a bit of an anorak over this timing issue.

Neither of you mention the extra 4 degrees of advance after setting the static timing with the pin in the flywheel. I guess that this is effectively taken care of by the adjusting until it sounds right?

I agree with all you say regarding the static timing and I am also of the old school where if it sounds right, it probably is. The problem is of course, as I intimated in my posting, that after setting up the static timing one is relying on the centrifugal and vacuum units to perform as they are supposed to in order to advance the timing as the engine speeds up and throttle openings vary.

I think that, in general, our engines are very forgiving for out of spec settings but the ignition systems were originally quite carefully designed to match and optimise the engine performance.

When my engine was rebuilt, I rebuilt the distributor with new bushes and thrust washers so that there was no play in the shaft. I tried to get new springs for the centrifugal advance but have not found any. Even Martin at Distributor Doctor could not supply any. Consequently I am not sure how well the advance complies with the curves in the manual. Hence my thoughts on using a strobe to see what happens as the engine speeds up.

I am trying to compose a short article for FP to share my findings.

[ChrisParticipant]

If you don’t remove the pin, you’ll need something stronger than a cup of tea.

An article for F-P would be lovely!

Chris

[Roger GrixParticipant]

Article has been submitted to Bryan.

I just needed that nudge to sit down and do it 🙂

Roger

[BernieParticipant]

Roger,

As you surmise, the fine timing “by ear” eliminetes the final 4 degree adjustment and will also go some way to accounting for wear or other imperfections in the distributor itself.

One tip for those prone to leaving the pin in the bell-housing – use a drill bit (shaft end in the hole).  Unlike a mild steel rod which bends and then becomes a nightmare to remove, a drill bit will shatter and the broken bits will fall to the bottom of the bell housing.  If one is so inclined, they can be removed by taking off the cover plate at the back but, out of sight, out of mind in most cases …..!

B…………

[Roger GrixParticipant]

Bernie,

As long as it is not one of those bendy Chinese drills. 🙂 🙂

Roger

 

[ChrisParticipant]

Good point about the drill bit.

And how clever of Citroen to include a plate for removing broken drill bits from the bell housing. Years ahead of their time etc…

[Roger GrixParticipant]

Hi again all,

I have come to trouble you some more.

In the course of writing the article for FP, all sorts of things have started to come to light.

It may well be that a lot of this has been discussed before but it’s all new to me.

I found this article on replacement distributors which shows the potential pitfalls of re-manufactured/substitute distributors and the worrying side effects.

http://www.theminiforum.co.uk/forums/topic/295669-distributor-advance-curves-re-manufactured-distributors/

I then started wondering about electronic units and had a look on the 123 site. I don’t know how many people are using 123 units but their site seems interesting.  They offer downloads of custom advance curves that you can put into your electronic units.  Has anyone used these or created their own custom curves?

https://www.123ignitionshop.com/gb/content/11-123tune-curves-download-page

I don’t know if I am interpreting the program for the Perfo engine correctly but it definitely seems to be based on the centrifugal curve in the manual. It starts at 700 rpm and advances to 24 degrees (engine) at 3400 rpm.

The vacuum curve however, (again assuming that I am reading correctly), appears to do nothing until a vacuum of 30 kPa and then at 31 kPa bangs on 20 degrees of advance. Not really what it is required.

I am hoping that there are members who can enlighten me.

Roger

PS Sorry, I have not worked out how/if one can put hyperlinks in messages.  You will have to copy and paste the links.

 

[David FaulknerParticipant]

123 ‘Citroen’ designated distributors come with a pre set selectable curve’s and cover the Perfo, 11D, HY, DS etc. etc. engines Roger.

Now in my other recent posts on ‘ethanol’ you will see pics of a burnt out valve from a Perfo engined Traction which was actually running a 123 electronic dizzy set for a Perfo Advance curve which looks a bit like the picture in your 1st link.

I took that distributor out a couple of months back as I wasn’t happy with the way the car ran and replaced it with a Ducellier manual dizzy copy (by Valeo) from Renel https://www.renelauto.fr/allumage-electricite/338-allumeur-adaptable-neuf-avance-a-depression-pour-traction.html for 65 euro

Even with the low compression on cylinder 3, the car started and ran better with the ‘old fashioned’ dizzy so it will be interesting to see how the car performs after the head rebuild, which will hopefully be by the backend of next week….

BTW here is the selectable ‘curve table’ for the 123 to see if it helps you

 

[Roger GrixParticipant]

Hi David,

Thanks for that info.  I am not looking at going electronic for a couple of reasons. Firstly from the point of view of originality, secondly repairability.

Looking at the figures in the table, the Perfo profile seems to be based on the curves in the Citroen manual.

Are the Citroen curves pre-programmed into the distributor?

I have downloaded the 123 software and loaded the file for the 11 from the list of downloadable profiles. I assume that these are custom ones developed by others. My interpretation of the profile program for the Perfo was correct and is completely wrong IMHO.

I must say however that the idea of being able to create your own profile without springs and weights is very interesting.

Good luck with the repaired head.

Roger

[Roger GrixParticipant]

Hi again David,

I have just read a bit more on the 123 site and see that the traction distributor is pre-programmed with the Perfo and 11D curves and is switchable. The programmable unit is a different model and lets you design your own curve.

Roger

[Norman AndersonParticipant]

Sorry for being such a moron, but I’m setting this up from the start….

Where is the no. 1 cyclinder and what is the firing order? Also, which was does the rotor arm move when running (as viewed from above) the 123 manual says you need to know this!

Guess the easiest way to find out when the no. 1 is on the compression stroke is to remove the rocker cover?

[David FaulknerParticipant]

No 1 at the front of the car – firing order is 1,3,4,2 – find TDC at no 1 and put a 6mm pin into the bell housing to ensure the flywheel is in the correct position. Insert the 123 dizzy, follow the instructions for wiring then turn the 123 until the internal LED lights up, lock the 123 down, REMOVE the 6mm pin and your good to go.

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