Lotus Elan

Lucas gold sports coil........

PostPost by: mark030358 » Tue Jun 28, 2005 3:47 pm

Hi there,
Can these be fitted to a car with a set of standard ignition points?


cheers
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PostPost by: steveww » Tue Jun 28, 2005 4:50 pm

AFAIK yes to the sports coil.

However IMHO it is also a good idea to fit an Aldon or Lumenition magnetic/electronic points. Fit and forget 8)
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PostPost by: nebogipfel » Tue Jun 28, 2005 7:08 pm

Mark, The only issue I can think of is are they 9v or 12v ie designed to work with a ballast resistor or not? Not a problem but you need to wire appropriately.


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PostPost by: mark030358 » Tue Jun 28, 2005 11:50 pm

Gents,
Thanks for that. I have the aldon ignitor system at the moment, but for some reason the tacho stopped working after I fitted an alternator. It was however working correctley with the aldon system before I fitted the alternator. Maybe a coincidence, so I was going to fit points just to check the tacho was indeed working.

Any suggestions as to why it should just stop? Very infrequently the tacho bursts into life for a few seconds then stops.

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PostPost by: type26owner » Wed Jun 29, 2005 12:03 am

The tach is normally a current sensing device. It should be connected in series to the white wire that supplies the ignition coil. The white wires are the ones which are switched on and off via the ignition switch.

The alternator output should be hooked to the brown wires. Brown means it's always at battery voltage. There is some danger with this arrangement if the alternator shorts out, the battery is also dead shorted. The normal solution to prevent a total meltdown is to add a fusible link to the alternator output so it can melt that link and open the connection in the event of an alterantor short circuit.

There should be a white wire going to the alternator though if you're got a 2,3 or 4 wire one. It's the supply for the field. Don't connect the white wire circuit that feeds the coil also to the field on the alternator. I don't have my manuals sitting in front of so I cannot stare at any circuit diagrams. There are a few good articles on the web that explain this stuff if you just google for them.

Did you connect the alternator battery terminal up to the wrong circuit? That would be likely reason the tach is not working.

I am going totally from memory on this stuff so I reserve the right to be wrong here! :shock:
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PostPost by: miked » Wed Jun 29, 2005 10:11 am

Mark,

My expeience is that a matched coil to the electronic ignition is best. Meaning, get an Aldon flame thrower coil. All worries over (about ?40 quid)

I had a lumenition with a Lucas gold on a plus two (fiited by another) and if the coil resistance was a tad to low causing greater current in the ignition ciruit. The history showed a failed module and it fialed on me. lumenition kindly repaired it and I added a small RS ballast resisitor to get the resistnce past the minimum. The car is still running on it, my mate has it.

Re Alternator, is this not a totaly unrelated problem. This circuit has nothing to do with the ignition a part from chaging or not charging which is a difference between say 12.6 (ish volts) and 13.8 (ish volts). + ve term being fed through red ignition light to WL to give excitation and chage indication.

As Kieth said the Tacho is current sensed via the white wire through the dash cut out switch. If the Aldon works the same current should be pasing through the same white wire and pulsing the tacho. If it were open the car would not run. Sound like Tach has gone "tits up"!.

Get it off to Speed and have a spot on voltage sensed one. You can rev with confidence.


Regards Mike

When do I get to see this car!
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PostPost by: type26owner » Wed Jun 29, 2005 3:00 pm

Since the tach is current sensitive then it's logical the hall effect switch ignition must be matched to the same current value as the points setup for it to indicate correctly. This requires the coil's primary circuit have just enough resistance to do this since it's the load. Follow the instructions for the type of coil that's needed. Also the hall effect switch is a solid-state device which has a maximum current threshhold upon which if you exceed it all bets are off as to how long it will last before going puff.

The dielectric components which comprise the dizzy cap and rotor are made of materials that can't standoff high voltage very well like the modern insulator material does. Hammering that stuff with more than 25k volts is ill advised and not necessary for the standard compression ratio of the twinkcam.
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PostPost by: mark030358 » Wed Jun 29, 2005 3:25 pm

Gents,
Thanks again, speedy here I come

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PostPost by: type26owner » Wed Jun 29, 2005 4:22 pm

Mark,
I forgot to include this summary statement. Suggest you also match the impedance of the new coil to the old one. I suspect the coils' primary circuit should have the same amount of windings so the eddy current field collapses at the same decay rate otherwise the tach will likely go bonkers.

Oh yeah, the tach starts to work when the internal solid-state voltage regulator in the alternator shuts off the current to the field to stop the alternator from overcharging. All these thingies must be right. My tach works perfectly with the Bosch 65 amp 3-wire alternator and the Pertronix Hall Effect Ignition and regular old style 25k coil.

If you bumped up the current output of the alternator compared to the generator then you would be wise to add some more heavy gauge wire to the battery output to handle that extra current capacity. The existing wire size in the loom could overheat could overheat and leak out it's smoke.
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PostPost by: miked » Thu Jun 30, 2005 10:15 am

Keith,

a question. I dont undersatnd what you are saying about the tacho with relation to the alternator. I have seen tacho termials on alternators and have used them on diesel gen' sets. But my understanding is that the tacho' only picks up pulses via postive through the ignition circuit to ground.

Has your system got an alternator connection.

thanks Mike
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PostPost by: type26owner » Thu Jun 30, 2005 1:53 pm

Mike,
No, two of the three wires on the Bosch alternator are connected directly to the battery. The third is the feed for the field coming from it's own circuit routed through the ignition switch. The wiring looms I buy from DBE are for the generator and have to modified for use with an alternator. My point is the circuit which feeds the ignition should not have any other load connected onto it. Typically the field of the alternator draws about 5 amps. The ignition circuit also draws about 5 amps. Add those two loads together on the ignition circuit and the tach would go nuts. Again, I have not looked at this stuff in at least 5 years so I reserve the right to be wrong.

Since I don't know which series of car we're talking about or the specific type alternator I'm groping in the dark here completely with just concepts. Going in with preconceived notions just provides amble opportunity to be wrong. Ya gotta start somewhere though. :wink:
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PostPost by: type26owner » Thu Jun 30, 2005 2:56 pm

Mark,
It's also possible you've got a new duff alternator. If a diode is leaking some AC waveform into your electrics this might adversely affect the tach. It's a reach at best since I have no idea how the tach circuitry actually works. A leak of several 100 milliwatts would drain your battery in about two weeks if left standing. Easy thing to check for with a scope.
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PostPost by: type26owner » Fri Jul 01, 2005 2:29 pm

Now that Mark has corrected the errant tach I realized my advice about the field hookup to the white wires is not quite entirely correct. The one place you don't want to connect the alternator field supply is BETWEEN the tach and earth. Attaching upstream of the tach on the same circuit is perfectly okay because that will not cause any current to flow through the induction sensing loop of the tach. Only the current used by the ignition should go through that loop.

I'm making it a four day long weekend today. :D Have to get my old Dodgy van to pass the rolling road smog test this time. Time to whip out the AFM and sort out the problems of that carbie.
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