Lotus Elan and Lotus Elan Plus 2 Forums

nmauduit wrote:

Andy8421 wrote:
Are the advance numbers displayed on the app just distributor advance (in crankshaft degrees), or does it also include static?

the advance value displayed is intrinsic of the distributor, and in crankshaft advance degrees : if you set the dizzy so that it has its zero at zero crankshaft (which I do for convenience, and which is relatively easy to double check via piston 1 if need be), then all values are actual advance values. If you set it at x degrees advance, then you need to add x degrees crankshaft to each value. There is a led witness light that indicates the zero reference for the dizzy, I try to set it carefully as it will be the basis of all subsequent dizzy timing operation (e.g. turning the dizzy 1° when reinstalling it on the block will add or subtract 2° crankshaft to the whole curve).

Thanks, that is as I understood it. The reason for asking was that TeeJay (above) mentions at the top of his post that he set static to 12 degrees before TDC, therefore all of his graphs would need 12 degrees added on to them to give the actual advance?

Andy8421 wrote: The reason for asking was that TeeJay (above) mentions at the top of his post that he set static to 12 degrees before TDC, therefore all of his graphs would need 12 degrees added on to them to give the actual advance?

the last graph (#3) which is close to what I use is meant to have the dizzy start at 0° crank :

it does start at 0 but this is for 0 rpm, and is just meant to ease cranking at very low speed. As soon as the engine revs above starter speed (say 200 rpm) there is advance, to the level of 12° around 1000 rpm for idle.

actually, since there are more points than strictly necessary, one can implement a little tweak to help stabilize idle around the desired iding rpm (a couple extra degrees advance before the desired idle, so that the engine is helped to go back to desired idle rpm if a bit cold or else hicuping) : cf. quaybook's graph zig-zag shape at low rpm

then the key point is a relatively fast rising curve (I have webers) to 2500 - 3500, and the max advance level (I opted for 34°, depending on fuel used, chamber compression and condition etc). Finally I implemented a smooth advance reduction above my max rpm limit (6500), not knowing how the system does the rev limiting (also set at 6500).

PS: I am not using "vacuum advance" (MAP curve adding advance to the main one according to manifold pressure, as shown in quaybook's post) since I have modified this entry to use a throttle positioning potentiometer.

Having completed just over 500 miles with my total nuts & bolts restoration, I’ve returned to this topic to update my current progress with the 123 Ignition unit.

Certainly impressed with the electronic unit, no points, no maintenance, better starting, easy to change / tweak curves and in my bluetooth version you can make changes while driving.

I have also taken onboard some of the comments previously made.

1) Yes there is more clarity if the unit is set up at TDC on cylinder 1 on the firing stroke.
I use a bar through the spark plug hole with a dial indicator, although my timing mark is accurate. Position the distributer for No1 spark plug, rotate the body clockwise until the green light illuminated and secure the position.

2) Because its set at TDC, you have to input the 10 or 12 degrees static setting, so removing the confusion at the higher revs, i.e. what you see on the 123 Timing curve is what you would see using a timing light and also what RPM you see on the 123 Dashboard Crankshaft Advance instrument.

3) My previous Curve settings were too advanced at higher RPM. I have changed the photos on my previous post (page 1) to correct this and to avoid any ongoing confusion.

4) All my curves are for Weber carburettors and Lucas Distributor No 41189A.
Also for reference to Miles Wilkins Lotus Twin Cam Engine Book, the C type cam has 10 degrees from 0 to 2000 RPM and the D type has 12 degrees 0 to 2000 RPM. From this it can be seen that the mechanical advance balance weight has an advance of 14 degrees.

5) As my engine has only completed 500 mile since rebuild with many new parts including a +0.060 inch oversize re bore with new pistons, I am limited to 3000 RPM with latterly the occasional 4000 RPM. So curve settings past this cannot be established at present.

Hi Trevor

You want to be careful to distinguish between crank degrees and distributor degrees when talking about ignition timing. Lotus did not do this properly and at time confused the two themselves and created much subsequent debate

cheers
Rohan

Hi Rohan.

Many thanks for your comments, to me it’s important that any information on this forum is accurate and therefore I am grateful to you or anyone who takes the time to make corrections.

I am aware of the past discussion re Crankshaft and Distributor RPM and many years ago, following comments by you on this forum, corrected my early Lotus +2 Workshop Manual, Technical Data, by changing “crankshaft rpm to Distributor rpm” then adding a column Crankshaft with double the rpm of the distributor.

I have just rechecked my corrected Workshop Manual and the Miles Wilkins book and I now find the information between the two are different when comparing the Distributor 41189A and Webber Carbs data.
So I am confused again and will take time out to recheck the data again, possibly to post copies of that data on the forum.


On page 1 of this topic, I posted the Ignition Maps for the 123 Distributor, certainly the mapping I ended up with works with my engine, so hopefully the Maps for the C and D type cam ones are a good starting point.

Any way Rohan, thanks again for your comments are always appreciated.

Off now to clear my mind and re approach the data.

Sorted the confusion between my Corrected Work Shop Manual and Miles Wilkins book re Ignition timing, the problem is that in the book the RPM under "distributor" are Crankshaft RPM. I've added in red corrected values.



Also on the next book page, I've added in red "distributor rpm" as in the photo below.



Finally the photo below are corrected values in my early Lotus Elan +2 Work Shop Manual.



Updated on 3 Nov, to correct the previous documents posted.

Those advance curves in the Miles Wilkins book for the 41189 distributor are not correct. These are the curves from the Ford Workshop manual for the Lotus engine - figures all at distributor (not crankshaft)

rgh0 wrote:You want to be careful to distinguish between crank degrees and distributor degrees when talking about ignition timing. Lotus did not do this properly and at time confused the two themselves and created much subsequent debate

Finally (hopefully) I have sorted my confusion with Distributor and Crankshaft RPM, thanks to Rohans gentle comment.

The Mechanical Distributor rotates (RPM) and at a particular RPM the balance weights start to advance, as the RPM continues to increase then the advance also increases.

Also Crankshaft RPM is double that of the Distributor RPM.

All straightforward and yes I did know that, BUT

What the issues where, is that both the early Work Shop Manual and certain parts of the Miles Wilkins book are inaccurate or not clear and I did not pick that up and then incorrectly used those in my illustrations.

So I have corrected both documents and also corrected my previous post, hope that resolves that particular problem.

2cams70 wrote:Those advance curves in the Miles Wilkins book for the 41189 distributor are not correct. These are the curves from the Ford Workshop manual for the Lotus engine - figures all at distributor (not crankshaft)

Thanks for those advance curves.

It's interesting that they are different from the Lotus Work Shop Manual and the Miles Wilkins book.
I note that the advance starts early and finishes before both the curves noted in the Work Shop Manual and Miles book.

It is easy to input those into my 123 Distributor and see how they perform, I will report back.

Took the Lotus out, after having input the data for the Ford Escort Twin Cam as provided by (2cams70), into my 123 Distributor.

Yes I did have a reason to go out in the 2nd day of “Lock down”, made sure of that.

Started immediately, after 3 pumps of the throttle and a little choke for approx 2 mins, getting it out of the garage.
It went very well, quick response to throttle, engine ran very smoothly even at idle. No backfire or spit back.

Progression was smooth through the gears, both at slow and fast throttle input.

As my engine has only run for 575 miles following a complete rebuild, I only went to a max of 3500 RPM, but as can be seen from the advance curve, the curve maxis out at 2400 Crank RPM anyway.

So I will be keeping this advance curve as my 123 Settings. Thank you 2cams70

During this session, I have produced Graphs which are included and as 2cams70 noted, it can be seen that the data in the Miles Wilkins are not correct. I must add that it is an excellent book and has been a valuable asset.
Does any forum member have his new book and has the data been corrected?

Have also noted that other forum members, who have posted results after Dyno Sessions, show that the advance curve continues up to a max of 34 crank degrees.
So the question is does the new Distributor technology improve on the old?

I'd be surprised if after a dyno session you are not able to keep adding advance such that you are all-in for around 34 degrees around 4,000 rpm? I agree that the rate of advance per the MW curve looks very slow.

I have a 123 USB dizzy in my Alfa Giulia and am looking to also fit a 123 to my Elan. Who did you source yours from, as there appears to be a variation in prices in the market?

Flying Banana wrote:I'd be surprised if after a dyno session you are not able to keep adding advance such that you are all-in for around 34 degrees around 4,000 rpm? I agree that the rate of advance per the MW curve looks very slow.

Thanks for the confirmation re additional advance up to 4000 RPM.
I will certainly give it a try, when my engine, currently being run in, has done more miles.

Flying Banana wrote:I have a 123 USB dizzy in my Alfa Giulia and am looking to also fit a 123 to my Elan. Who did you source yours from, as there appears to be a variation in prices in the market?

As I am also based in the UK, I purchased in the UK from SC Parts Group, see link.

Link: - https://www.scparts.co.uk/sc_en/warehou ... 34923.html

I also looked at purchasing from the manufacturer who is based in the Nederland’s, see link.

Link:- https://www.123ignitionshop.com/gb/tune ... tooth.html

But as the costs were almost the same, I decided to purchase from the UK.
Costs UK £399 + £12.95 delivery = Total £411.95 GBP.
Costs Nederland’s Euros 445 + 17 delivery = Total Euros 462 = £411 GBP.

There is possibly a benefit when buying from the Netherlands, which I found after purchase. That is of returning the unit for free repair outside of the warranty. I should add that the person concerned was a reviewer of Motor related product, so perhaps a good example for Public Relations.

Spurned on by this post I too have acquired a 123 Bluetooth distributor and about fit. I have not decided on coil yet, but does anyone know why 123 appear to recommend a 3ohm coil?

Peter

Peter +2 wrote:Spurned on by this post I too have acquired a 123 Bluetooth distributor and about fit. I have not decided on coil yet, but does any know why 123 appear to recommend a 3ohm coil?

Peter

I've been using a red Bosch "performance" coil (1.8 Ohms, supposedly 33000V spark - no ballast) since installation 5-6 years ago, no issue so far (I understand if you go below 1.8 Ohm you may pullm too much current and risk damaging the circuit)