170 replies to this topic

[gaspen]

Please shine a light in my head about the advance curves theory.

 

Here is the example for 41026 which is on my 850. How should I interpret it ?

 

The black diagram is from this source :  Book2 (1st pic) The green is from the AKD4935 manual (2nd pic)

 

These datas shows the total advance (static + centrifugal) or only the centrifugal ?

 

In case of the green digram : I guess that the primary spring is working 700 - 1300 rpm, secondary joins above 1300

 

But what is that break at 900 rpm ? 

 

 Képkivágás.JPG   7.81K   0 downloads

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Attached Files

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[Spider]

Just one thing before we go too far, the figures and usual tests are done with a decelerating speed. So you'd take the distributor up to a speed over the point where you get full advance, then slowly wind the speed back and start plotting the numbers. I'm not sure here if that's how you've got your numbers ?

It does appear your machine works though !

[gaspen]

Just one thing before we go too far, the figures and usual tests are done with a decelerating speed. So you'd take the distributor up to a speed over the point where you get full advance, then slowly wind the speed back and start plotting the numbers. I'm not sure here if that's how you've got your numbers ?

It does appear your machine works though !

 

What you see in my post are not my measured values. These datas came from the 2 different sources for the same dizzy (25D4 - 41026)  which I put together in one diagram. They are pretty different 

 

Anyway the machine will work   I'm just make it nicer these days. I will make an adjustbale degree wheel and I will install an on/off switch into the resistor circuit for the electronic dizzys. I will tkae more picture tomorrow.

 

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[Spider]

Ah !

There's a spreadheet getting around with a few hundred (or more) Lucas Distributors that's been circulated for a few years, it's full of errors and doesn't seem to have a source. The figures in your first line appear to be from that spreadsheet.

The particular figures I have looked up over the years in the factory workshop manuals all do seem to be right.

 

When I get a chance, I'll have a look in the Lucas book

[gaspen]

There's a spreadheet getting around with a few hundred (or more) Lucas Distributors that's been circulated for a few years, it's full of errors and doesn't seem to have a source. The figures in your first line appear to be from that spreadsheet.

 

Exactly !

 

 

 

When I get a chance, I'll have a look in the Lucas book

 

 

Is there a Lucas book ?! I searched on web for weeks but can't find any.

 

I dowloaded this one but it's include just a few.

 

MINI Mark 3 1969-1976 Workshop Manual | carmanualsdirect – Car Manuals Direct

[Spider]

Is there a Lucas book ?! I searched on web for weeks but can't find any.

 

I got mine back in the early 80's and they were well out of print then, The book I have only covers up to about 1971 - 72-ish at a guess. There is later books than the one I have, I have some copied pages. I'm sure if you keep an eye out for them, they will come up for sale from time to time.

[68+86auto]

Later Lucas technical data appears to be microfiche only. I almost bought a set but was incomplete. I have been unable to find it in any other format.

 

This data from about 1963 is what I use. It appears to be taken straight from Lucas data, no reformatting or anything. https://archive.org/...-specifications

 

This manual may also be of use to you: https://archive.org/...raph-410-manual

[gaspen]

Some pictures for you

 

I hid the resistors to the motor frame. 2x 4.7ohm/50W. I've put some thermo paste to them also.

 

And I spent many hours figuring out the adjustable degree wheel from the junk I have. I am not so satisfied yet as it is a little bit loose. And I had to make another frame to make it concentric.

 

At the end of the day I'v tested the 41026. Look the red diagram, interesting curve    I guess it's becuase the wear in the unit. Tomorrow I'll test some new dizzys, wndering how they perform.

 

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 Képkivágás.JPG   77.75K   1 downloads

[gaspen]

What could cause these errors ? 

 

1st pic : a "continous" light instead of a break : maybe too much gap at reluctor ?

 

2nd pic : look the bottom arc, there is two break in the light, but only at 1 one "cylinder"

 

Funny but both errors disappeared after some "warm up" 

 

 

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Is it a good idea to publish my measurements here ?

Edited by gaspen, 28 December 2025 - 08:17 PM.

[68+86auto]

What could cause these errors ? 

 

1st pic : a "continous" light instead of a break : maybe too much gap at reluctor ?

 

2nd pic : look the bottom arc, there is two break in the light, but only at 1 one "cylinder"

 

Funny but both errors disappeared after some "warm up" 

 

 

20251228_112150.jpg 20251228_111828.jpg

 

Is it a good idea to publish my measurements here ?

 

The first one looks like a machine issue.

 

Did the second one have points?

 

Yes it would be good to publish them on here somewhere. Especially the new distributors which have unknown curves.

Edited by 68+86auto, 29 December 2025 - 10:37 AM.

[gaspen]

Did the second one have points?

 

No. These pictures taken while I've tested the same BAU1962MS. I have two of these now, both compared to the 41418 curve.

 

Now I see that an accurate degree wheel is a must.

 

1st diagram : from my own 1975 / 998, purchased 2 or 3 years ago. (right one on the picture)

 

2nd diagram : bougth by my friend to his similar car last month. (Left one)

 

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I've tested the GEU930MS also which I will put to my 850. I compared it to the 41026 curve but I have two sources for it with different data. One is from the MK3 manual, other from grabbed from a french book called "Revue Technique Automobile". Maybe this one has "type" mismatchs as it shows max advance at 4400 instead of 3400 (?) And I don't really understand the blue line on the lowe range.

 

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My old, points 41026 and 41418 both show very inaccurate readings, it's time to retire these.

 

 

 

 

[gaspen]

Just found this, maybe you interested

 

lucas_cav_girling_equipment_1971-1972.pdf

[gaspen]

Does any of you has data for the new dizzys for reference ?

[68+86auto]

Does any of you has data for the new dizzys for reference ?

 

I have tested a minispares ADU5789 and C-27H7699. It seems that sharing the data using my phone is too difficult. I will try to remember in about a week when I'm home.

 

One of my many projects to do is build a database of distributor data that people can add to. I currently have it all in google sheets and it is not ideal.

Edited by 68+86auto, 31 December 2025 - 10:49 AM.

[gaspen]

I have these old graphs but I am not sure if they count with static advance or not

 

https://photos.app.g...seHDLUzjjpgs9x8