Lotus Elan

Aldon ignitor and an RV1 tach

PostPost by: jeff jackson » Tue Aug 07, 2012 8:18 pm

Hi All,
After many years of terrible idling and trying all sorts of things, good and not so good, I have finally ditched the 23 D distributor and leads.
I have recently bought a 43D, Magnecor leads, a new distributor cap and an Aldon Ignitor (all from Sue Miller).
I am yet to fit it all into my 72 +2 but I suspect some problems with my RV1 tach. I have searched the forum for any tips on this, some have bouncing tachs others not.
Has anyone done this (slight) mod to their Elans with or without any isuues?
Any comments gratefully received.
Kind regards
Jeff 72+2
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PostPost by: RogerFrench » Wed Aug 08, 2012 3:39 am

I've done it to both Elan and TC Europa, and in both cases the RVI tach bounced.
I got them both rebuilt.
1967 Elan S3
1972 Europa Twin Cam
2005 Elise
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PostPost by: stugilmour » Wed Aug 08, 2012 4:09 am

I used my stock RVI with both an electroonic unit fitted by the PO (not sure of brand) and a complete Pertronix replacement dizzy with no bouncing. However it has just recently decided to not go above about 5,000 rpm. Was going to call tomorrow to check out servicing or conversion options to RVC. The electronics inside look pretty grim. Was hoping service to RVI would work to avoid any wiring hassle. Tach did need adjustment of the trimming resistor to read correctly though. I did not use a loop in the inductive bridge; just ran the coil wire straight through. Powered the Pertronix separately.

If you are unsure about the tach readings, I made a table of rpm to speed in all five gears in David's excellent spreadsheet. I then compared calculated rpm at GPS measured speed to the tach to adjust it to read correctly. Recommend doing this even if the tach 'works' with no bounce; was amazing how far out it was.
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PostPost by: mcclelland » Wed Aug 08, 2012 10:26 am

Hi Jeff,
I used an Aldon unit in my last plus2 for a few years without any problems. I now have an Elan S4 with Luminition optronic electronic ignition and its fine, been in the car for 5 years without problem. I heard of the bouncing tacho problem and purchased a new tacho through fear it would happen to me. Its all been fine and the new tacho has never left its box.
Hope this helps, Im sure we all have different stories....
Regards, George...
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1973 Plus2 S130/5
1994 Elan M100 S2
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PostPost by: simonknee » Wed Aug 08, 2012 10:42 am

Try it. If it works leave it. If it doesn't or if it bounces later send to speedy cables for conversion.

Job done

Simon
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PostPost by: rgh0 » Wed Aug 08, 2012 11:28 am

Just dont follow the wiring instructions and power the electronics from the coil positive terminal as this is what usually causes the problem as the pulses in the elecronics add to the pulses from the actual ignition and casue the tach to bounce as it counts both sets of pulses.

Power the electronics from another source independent of the power feed to the coil.

If it still jumps then you need to fix the tach electronics. It can be a simple capacitor replacement or you can do a full conversion to a voltage triggered tach if you want.

cheers
Rohan
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PostPost by: bob_rich » Wed Aug 08, 2012 12:05 pm

Hi Jeff

I fitted to my +2S a home made ignition unit (B 4 my current strip down and rebuild) the usual problem is the RV1 tacho need a complete interuption of the current (i.e points open) to work. if other leads had been taken from the coil + or SW terminal the current from these may upset the tacho. I had to move such an accesory lead then all was OK. This includes the small current that powers the electronic ignition. Ignition modules that are self power i.e have only 2 leads may not work with the RV1 unless modified.

hope this helps best of luck

Bob
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PostPost by: jeff jackson » Wed Aug 08, 2012 5:01 pm

Hi All,
Thanks for the replies.
From all the comments am I right in thinking that the Aldon just needs +12v steady voltage, therefore drive the tach from the coil?
Regards
Jeff
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PostPost by: pauljones » Wed Aug 08, 2012 6:02 pm

Jeff,

Having just read your post,id like to comment.

I ran mine,ignitor 2,for a short while.It was wired to poss and neg of the coil.The coil had its own power suply direct from the starter solonoid and the tach from else where,not sure really.

In this configuration I had no problem once I had made all the connections secure.

Paul
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PostPost by: simonknee » Wed Aug 08, 2012 8:07 pm

Jeff,

How you drive your tach is dependent on your tach type.

RVI it is: ignition -> tach -> coil+ve
RVC it is: ignition -> coil+ve ... coil-ve -> tach

points are always connected to coil-ve
electronic ignition connected to coil-ve but also needs +ve power from somewhere e.g. +ve spade on coil or from another more direct +ve connection.

BUT

I suggest you forget all about your tach for now.
Install your new bits and get your engine running sweet again.
Just do it by the install instructions
Once this is all done then look at what your tach is up to.
a. no problems then no problems
b. bouncing then try a different source for the +ve on the ignitor (as per Rohan)
c. still bouncing then get your RVI tach converted to RVC and re-wire as necessary.

Simon
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PostPost by: bob_rich » Wed Aug 08, 2012 8:53 pm

Hi Jeff

Just looked up the Aldon data on the web
it was on the link http://www.pertronix.com/support/manual ... 12vneg.pdf

If this is what you have then I have done a sketch showing how I would connect it with an RV1 type tacho
I have never used the Aldon but have fixed and repaired a couple of RV1's they do not like a small continuos current powering other circuits flowing through the wire that goes through the tacho loop

hope this helps best of luck

Bob
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PostPost by: stugilmour » Wed Aug 08, 2012 10:09 pm

Simon's post outlines what I did, and it worked for a while.

I am now at Simon`s last step C, and I am sending it off to Nisonger for conversion

http://www.nisonger.com/electric-tachom ... rsions.htm

I spoke with them on the phone today, and they mentioned they have seen several different failure modes of the RVI with electronic ignitions, including bouncing tach, tach reading double, complete failure, and apparently my symptom which is essentially reading 10% to 15% low and not getting over about 5,000 rpm. I had only heard of the bouncing tach failure.

The cost for conversion is going to be $360. I forgot to ask if it would be cheaper to just have it repaired as an RVI. Bit of a pain as I will have to run an extra wire to the from the negative terminal of the tach to the re-built tach. Figure it is all better than risking over revving the engine though, and the rebuilt tach should work every time. They recommended I tell them what brand of ignition is being used and they will check it works for sure.
Stu
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PostPost by: simonknee » Thu Aug 09, 2012 3:52 pm

bob_rich wrote:The cost for conversion is going to be $360.


Just been talking to Speedy Cables about them about getting a clean tach pulse for my afr logging system
The RVI - RVC conversion is ?75 + VAT + carriage
Even with the cost of sending it from the US this is a damn sight cheaper.

And it comes back looking like new with the correct writing on the faceplate
Last edited by simonknee on Fri Aug 10, 2012 9:52 am, edited 1 time in total.
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PostPost by: jeff jackson » Thu Aug 09, 2012 7:39 pm

Hi All,
Thanks for all your helpful replies. I will do the conversion over the weekend.
But look what I found on the Morgan owners site, how to convert your RVI to RVC.
Kind regards
Jeff
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PostPost by: jeff jackson » Fri Aug 10, 2012 5:18 pm

Hi All,
I have removed the tach, see photo. This does have RVI on th front, but looks like it could have been modified by Renown Instruments of Durrington in Wiltshire. (Not sure if they still exist!)
I have attached a photo of the back of my Tach, does this look like anyone else's RVI?
Thanks for all your help,
Jeff
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