Lotus Elan

Advice on dizzy rebuild

PostPost by: Craven » Wed Dec 04, 2019 8:39 pm

Value and stability of Dwell Angle is inconsequential if the distributor is fitted with one of these internal electronic units. One of their advantages is the electronic control of the dwell, being fixed at an optimum time, around 10 milli-secs. At low speed using conventional points the coil has more than enough time to ?charge? that can cause over-heating.
Nice article here
https://motochassis.com/Articles/Ignition/Ignition.htm
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PostPost by: alanr » Wed Dec 04, 2019 10:20 pm

I would agree that electronic units overcome the shortcomings of wear and instability of a points setup and for a race car setup it is very necessary to have this type of electronic module. However they all seem to have reliability issues and when they go wrong they just stop working, dumping you at the side of the road. They either work or they don't. There is no get you home possibility of sorting the problem at the roadside.

I would suggest that a classic road car that will probably only do a couple of thousand miles a year the absolute simplicity and ease of use of a points/coil setup definitely has distinct advantages.
This is just my view of course, the choice is obviously yours... :D
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PostPost by: Mazzini » Wed Dec 04, 2019 10:20 pm

JonB wrote:Hi Mazzini. Of course I searched! But it returned hundreds of results with the words "distributor" or "overhaul" in it - in other words, 99% irrelevant to my question.


I guess I must be a lot luckier than you.
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PostPost by: Craven » Thu Dec 05, 2019 12:40 am

I use the opto Lumenition setup.
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PostPost by: JonB » Thu Dec 05, 2019 9:21 am

Regarding roadside emergencies, I think it would be in order to carry a spare top plate with a set of points mounted on it, with the gap or dwell angle preset for the distributor. It is then a matter of removing two screws to swap the plates over if the ignition module fails.

So, consensus seems to say ?avoid the pattern distributors? and ?use DD to recondition a Lucas distributor?. Do we include the 123 unit in the ?pattern? grouping?
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PostPost by: RichardHawkins » Fri Dec 06, 2019 5:43 pm

John,

You might like to consider the electronic options. I have decided to use Electronic Distributor-less Ignition System, mainly because I am not happy with an ignition source under the carburettors.

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PostPost by: Andy8421 » Fri Dec 06, 2019 10:28 pm

I have often wondered whether moving from a points system to electronic changes the timing curve. The points must have provided some measurable drag on to the quadrant/cam which in turn must have been overcome by extending the bob weight springs and altering the timing slightly.

An optical system wouldn't have this drag, and presumably would have a slightly different curve.

Has anyone investigated this?
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PostPost by: rgh0 » Fri Dec 06, 2019 11:04 pm

When I changed from points to optically triggered Lumenition for my Plus 2 and Esprit many years ago I checked the advance curve before and after and saw no significant change across the rev range

cheers
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PostPost by: SENC » Fri Dec 06, 2019 11:54 pm

My initial plan was to go electronic, but as I read through all of the threads here I realized I was trading off one set of risks for another and that the best investment would be to have a good back up/recovery plan. This is what led me down the road I chose - a "new" old stock distributor built to suit, and some backup parts including parts to rebuild my original as a backup. Definitely not the cheapest solution, but no more than the electronic options and resulting in backups that I'd need to add anyway to electronic options. Also a return to original (from an older distributor that may have shaft wear) to reduce the number of variables in performance impacts rather than adding to them with a new/different system. Not saying this is the right decision, just mine. It also fits better with the general reason I so enjoy working on this car - the analog/mechanical technology that I can self-learn and work on rather than the computerized and overly electronic technology for which I'm not so equipped.
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PostPost by: Quart Meg Miles » Sat Dec 07, 2019 6:03 pm

In fifty years and loads of miles I've only had one problem (which caused two breakdowns) with my standard distributor and that was in the first year. The detent retaining the rotor arm fell out and shorted the spring to ground, stopping the spark. It flipped out while I was poking around, though I didn't know what it was, and I continued my journey. Then, a few weeks later, it jammed the bob-weight plate against the unit's body and the helical gear broke and fell into the sump.

I check the points every few years and changed them this year after about twenty years wear. I worked in electronics all my life and I'll stick to bits of metal in my car, thank you!
Meg

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PostPost by: MarkDa » Sat Dec 07, 2019 6:24 pm

Good to hear that you get good results from points.
There are those who will say that the fact that they are 20 years old explains why they lasted so long :D
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PostPost by: 2cams70 » Sat Dec 07, 2019 11:19 pm

If you don't want to go full electronic you can always go to the "transistor assist" type that still retains the points. I've built several Silicon Chip DIY kits over the years and have had a lot of success with them. The "transistor assist" reduces the current flow through the points to virtually zero so they last a lot longer. The only thing that then happens slowly over time is that the points plastic rubbing block wears so whilst not totally maintenance free it does cut maintenance down considerably. They also incorporate dwell extension - i.e the points are artificially closed electronically soon after opening rather than mechanically to maximise the magnetic flux build up in the coil between spark firings and hence maximizing spark energy.

They even have a fully programmable version with MAP sensing, knock sensing and also the option of retaining or deleting points. I have collected all the bits to build one (around $200 worth - i.e much cheaper than a commercially built unit) but like most things just a matter of trying to find the time!

http://archive.siliconchip.com.au/cms/A ... ticle.html
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PostPost by: billwill » Sun Dec 08, 2019 2:05 am

I think that the Chinese designers (or copiers) are good, but I suspect that the persons doing manufacture are on piece work rates and that the Chinese quality control procedures seem to be poor.

This means that you CAN get a GOOD replica but are just a likely to get a bad one.
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PostPost by: 2cams70 » Sun Dec 08, 2019 3:49 am

The Silicon Chip DIY electronic kit was designed right here in Australia. It can do practically everything a 123 system can do and was designed way before the 123 was. You can't program it using a smart phone of course as it was designed around the time the first iPhone was released!
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PostPost by: MarkDa » Sun Dec 08, 2019 9:13 am

I think these "assistance" type ignition systems are used in some classic car racing series in the UK that have to retain points.
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