Rev counter works with electronic sparks !!

[alexblack13]

How come I did not need to 'convert' my rev counter to work with the electronic ign system I just fitted (Magnetronic) I very nearly took it back out and spent even more dosh on this. (I am over the worst!!) It works perfectly. How come? I was told I would def' have to have it altered.. Anyone know why?

Beats me..

AB...

[rgh0]

There is no reason why the standard current sensing Lotus tach will not work with electronic ignition provided 3 things occur

1. The power for the electronic ignition is taken from a separate source not from the postive terminal on the coil. If taken from the coil it add more current pulse making the tach jump or read wrong. The installation diagrams for electronic ignition often show the power being taken from the coil positive as its a convenient location and does not upset voltage sensing tachs which all modern tachs are these days
2. The electronics do not add current pulses or other spikes in the coil current beyond what is driven by the distributor.
3. The aging electronics ( particularly the capacitors) in the Lotus tach are still OK and not failing so that the tach becomes super senitive to electrical noise in the power suppler or sensing circuit upsetting its reading
.
If all 3 are OK then it will work

cheers
Rohan

[alexblack13]

Well 2 out of 3 must do it ok. I have it wired (as Instructed to do as you mention) from the pos' side of the coil.
The systems wiring is set up to be so wired also. Might be something to do with the latest tech' ? Mike stuart fits this type all the time now and reports V few prob's with the rev' counter. Mike runs lots of clients in classic racing all over the country.

I am just happy I did not have to take out the instrument and spend more money on the thing.

Thanks for the info Rohan.

AB..

[rgh0]

Hi Alex
Interesting that you have the power supply from the coil positive and the tach reads OK.

Suggests that the Magnetronics electronics dont draw enough of a current pulse to trigger the tach or that any current pulse occurs at the same time as the pulse for the ignition itself so as not to create anouther pulse for the tach to read.

whatever the case as long as it works

cheers
Rohan

[alexblack13]

Hi Again, yes beats me too...! I was sure I would have an issue here and am very happy not to. Could it be a breakthro' Brilliant little device and so easy to fit. I am a convert. Trying to get to the dizzy to service points etc...Argh!!

Happy days. What a difference in the car's performance also. Wow. I would not have believed this had I not done it.

Cheapest place to buy turns out to be Epay by the way. A few quid less then the ex VAT price from the normal suppliers.

AB....

[Jas]

Hi Alex

I was one of the guy?s trying to convince you to have your rev. counter changed.
My rev. counter was jumping all over the place with my Aldon Ignitor, and I was going to have my rev. counter modified. But then for spring I accidentally reversed the polarity on the coil, stupid I know, it blew the electronic module and I had to buy a new Aldon unit.
With the new Aldon Ignitor, still the old version, my rev. counter is now behaving like it should, and I haven?t changed anything else. Beets me?

[elansprint71]

These things all work by black magic.
We have just fitted electronic ignition into my Son's Mini; it comprises a tiny module in the dizzy and new rotor arm with magnets. The cost was 8 GBP!!! and it works superbly.
If you look it up "Britpart" on t'Internet you will, I'm sure, find one suitable for the Elan's Lucas unit.

[dlbarnes1]

I've seen information that seems to indicate that the magnetic trigger causes little or no interference with the tach compared to the photo-optical type.
Anybody know anything about this for sure?
Dave - 72 Sprint DHC

[rgh0]

The Lumenition optronic optical sensor system I have run on both my Elan and Plus 2 with no problems with the original tach.

regards
Rohan

[StoatWithToast]

Hi,

I used to have an Aldon fitted (though I didn't know) the rev counter swung about (especially if I used the electric windows), but I assumed it was poor electricals. When I took the engine to get tuened up the scatter was very high, so then I thought the rev counter was just trying to keep up.

At the start of the engine rebuild I realised the Aldon kit was fitted and decided it needed replacing. After asking around and finding the 123 systems pretty much unavailable for the twinc I plumped for the Luminition Optronic system.

The first fire up attempt was last weekend, but no joy. A lot of diagnostics got it working this weekend, and it is solid.

The problem is the signal wire to the rev counter - with the system wired as described (as Rohan says with the power feed connected to the +ve on the coil) there is simply no spark produced. It does something so odd that the new electric fuel pump actually goes a bit manic and pumps like mad, but too weakly to actually move any fluid.

Obviosly the coil -ve terminal is at the battery positive with the only the primary coil in the way, meaning the whole line has a rather higher voltage than it was designed for... any ideas of what I can do to get it to work?

I've searched on here, but I have yet to find any info on what is needed to fix it (short of a new instrument).

Cheers,

Dave

[billwill]

Insufficient information...


What kind of Rev-Counter is it and has it been converted to voltage sensing instead of the original Current-Loop sensing? Was it converted from positive earth to negative earth?

Does the engine run correctly with the rev counter disconnected.

[StoatWithToast]

Engine works fine without the rev counter being connected.
If the counter is connected then when switch the ignition over the dial blips up to 1,000 RPM, back to zero then a second or so later it blips back up to 500 RPM, drops back to zero and stays there, even when the starter moter is spinning the engine.
The dial says neg earth, and is a Smith's dial with the blue light for high-beam lights and a red for the ignition light; it's a Sprint, so I assume that was -ve earth was normal by then.
I'm not sure if the dial has been messed with, but I don't think it has.

Cheers,

Dave

[billwill]

The portion of the elan wiring that relates to the ignition and tacho is basically fairly simple & is shown in this diagram.

Make sure each of the contacts and the sensor loop are well made.

Your symptoms sound as if maybe the case of the tacho is not earthed properly.

Ignition Coil and tacho simplified circuit.