Lotus Elan

Dizzy

PostPost by: miked » Sun Jan 29, 2006 2:53 pm

I am running an S4 with stromberg set up. I am ever so pleased with it performance except I seem to eat Dizzy caps.

I went for the Aldon igniter and thought I would have the mactched kit and put the Flame thrower coil on (more as match). I have noticed that after a while, maybe several thousand mile or recently several hundred that I develope a slight hesitation at about 2000 rpm. When I change the cap it clear and away we go. I had this on a plus 2 with a gold coil and Luminition. My friend bought the car and he has had sevral caps. Is it possible that with the high output kit I have that I am over stressing the old stlye black bakalite (spelling) Lucas dizzy caps with the higher voltage. I have bought them all new, they are not old ones. Are there better caps out there?

I will ring Aldon tomorrow as perhaps they do one with better electrical withstand insulation propeties. As I remember, Keith may have mentioned about the problems of doing this some time ago.
Me working with electric too!! :oops:


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PostPost by: Matt7c » Sun Jan 29, 2006 8:49 pm

Mike,
I have the Aldon Ignitor and I use a Gold Coil with it. However, I recall that my fitting instructions were quite clear that a high power coil was not recommended. Seemed odd, though, that Aldon's own instructions say to use a standard coil, yet I recall they market the Ignitor and Flame Thrower as a matched set for some applications. Have you tried a standard coil? Might be cheaper than tearing through dizzy caps?
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PostPost by: ppnelan » Sun Jan 29, 2006 9:37 pm

I think they recommend you DON'T use a high output coil because it may overload the amplifier (LOW tension side). If you have a problem with insulation breaking down on the cap then that is the HIGH tension side. As you say, it sounds like the output is too much for the old caps.

I had a similar problem with a rotor arm once. It was a non-Lucas 'new old stock' cheapie and one day it just stopped insulating. It was moments after I had commented on how reliable the car had been near the end of a several hundred mile trip ! Fortunately we were only a few miles from home, and I had a spare (Lucas) one...

You might want to check the rest of the HT circuit - are the leads good enough quality for a modern high power system ? Maybe the insulation breaks down and 'leaks' when hot (Stromberg engines can get quite hot), then 'recovers' by the time it's cooled down and you've fitted a new cap ? Try clipping them away from parts of the hot (& earthed) engine, particularly sharp edges where sparks are more likely to 'jump'.

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PostPost by: steveww » Mon Jan 30, 2006 10:09 am

I have found some variable quality with dizzy caps and rotor arms. I have had the conductor part company with the rotor arm :shock: When you pull the dizzy cap off have a good look at the contacts in the cap. I have seen these badly pitted after just a short time. More to do with poor quality than high voltage. If you are using solid copper leads you should use resistor plugs or caps.

The Lucas 23D4 was used on a number of British cars so you can get these bits from many suppliers. I bought the current cap and rotor arm from an MG specialist and the parts are a better quality. Depends on where the retailer gets their parts from I guess.
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PostPost by: type26owner » Mon Jan 30, 2006 2:41 pm

Mike,
Close the spark plug gaps down to .020" to lessen the punishment the aluminum contacts in the cap have to endure. This will reduce the electric field potential allowing the spark to jump the air gap at a lower voltage creating the plasma. Once the plasma is formed the bulk of the current flows at only a few hundred volts. This is also better for the coil since it does not have buildup to high a voltage and suffer from the time delay of collapsing a high voltage field. IIRC, there is a problem with running the coil at lower voltage and that is it gets hotter. Provide it with enough airflow for cooling. Never idle for a long period stationary cause that's when it really cooks.

This will slowdown the rate of oxidation from the ozone. Aluminum oxide in an electrical insulator, a very good one. For each .001" thick oxide coating thickness that will standoff 1000 volts. Aluminum is just about the worst metal to make an in-air arcing electrode from. Lucas brass caps are still available but are five times the cost of the crappy aluminum ones. However, they last five times longer.

For those that still have the points then set the dwell and ignore the actual points gap. Excessive dwell will overheat the coil too.

The Ignitor II if it's ever offered for our dizzy will adjust the dwell on the fly and shut off ignition if the switch is left on by accident and the engine is not running. Whining to the manufacturers about when it's going to be introduced helps.

The flame-thrower is a gimmick. Having more windings then necessary is dumb because the field collapses slower. This will cause a high rpm miss sooner then a lower voltage coil. The trick is have enough voltage to spark the flame kernal at the highest cylinder pressure but not so much that the coil can't recover and collaspe the field completely before it's energized again. A 25k coil is the perfect match for the stock twinkcam.
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PostPost by: ppnelan » Mon Jan 30, 2006 3:01 pm

Keith,

Is closing the plug gaps detrimental to efficient combustion & smooth running?
Isn't is better to have 'big fat spark'? - that's what I thought part of the idea of electronic ignition & a high output coil was, to make a bigger spark than the standard (points) system for better more consistent combustion.
Or does it just make up for other problems, such as the one you noted of oxidation of the aluminium 'contacts', so you don't have to keep everything in perfect (electrical) condition? That & poor quality petrol...

Kind regards,
Matthew
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PostPost by: type26owner » Mon Jan 30, 2006 3:49 pm

Nope, once the flame kernal is lit off it obeys the physics of fast chemical reactions. The actual energy to ignite an ideal mixture at atmospheric pressure is equivalent to a static electricity charge of a few hundred volts. Under idling pressure that value goes up to around 6000v. At maximum cylinder pressure it takes 18000 to 20000 volts typically. Opening up the spark plug gap just forces the voltage up but improves nothing. Don't believe the hyped bullshit. It done to separate the gullible from their money.

BTW, Steve is correct in that resistor plugs are a must for solid core metal spark plug wires.
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PostPost by: miked » Mon Jan 30, 2006 8:51 pm

Thanks guys for your help. Keith,it sound like you have really looked into this. I will close the gap and also examine the cap ally' electrodes. I will look at getting hold of a standard coil. It does all sound like Kv for Kv sake. I think I have been separated from my money! :?

Re: The leads, they are newish. Went on with the prevoius cap about 1500 miles ago. They are the carbon fibre silicone modern type.
I have liitle rubber boots on them near any sharp bits but did route them from the rear (not over the top between the carbs). The problem does go away for a relatively long time with a new cap but when I think back to when I first put it on the road I had the misifire within 400 mile of new. I did not attend to it and it did go worse but only showed with heat. In the end I stumbled home. At the time I thought it was the Igniter but tried a cap and rotor arm. The new cap cured it. I put the old rotor back. I have changed this since. I have had a few set of lead and everything comes back to the cap.

I carry a spare cap and two rotor arms. I think it is time it was sorted out.

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PostPost by: type26owner » Tue Jan 31, 2006 2:02 pm

Mike,
Keep the coil and carbon plug wires you already have but just reduce the spark plugs gaps and that will reduce the peak voltage. The bakelite is not the greatest electrical insulator and spanking it with high voltage is just asking for it to break down quicker. Keep popping the cap and scraping the oxidation off every few months. The wider the airgap between the rotor and electrodes on the cap the higher the resistance becomes for the spark to follow the intended path to earth and fire off the cylinders.

The Ignitor magnet disc that installs under the rotor raises it enough so the rotor can rub against the cap. If it does then the rotor is only a few hours away for shorting through and stranding you along side the road.

I was lucky to find a small supply stash of discontinued brass dizzy caps and now have a lifetime supply cause I bought them all. :D
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PostPost by: paros » Sun Feb 05, 2006 12:04 pm

Just to mention a problem I have had that ties in with the questions. I use and Igniter 11 and the so called matched coil but not very impressed.

However after reading about dizzy caps etc I went and looked at something I had meant to check on for months. Namely the HT modern 8 mm silicone lead that goes from the coil to the centre of the dizzy cap. The central connection in the cap needs the wire to go in a long way for it to make contact with the copper in the cap. To do this the little waterproofing sleeve on the HT lead needs to be forced down the wire by a good half inch BEFORE pushing the wire into the cap.
Mine was not and loads of carbon and dirt.
Suggest its worth a look
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PostPost by: miked » Tue Feb 14, 2006 10:13 pm

Keith,
I talked to Aldon today just to see what they would say. The main tech' guy was out and the sales guy went and had a chat with another tech guy. His advice upon return to the phone was that perhap I may be better with a Lucas DLB 105 coil at a lower voltage as it was more suitable. :roll: Also, perhap they didn't make dizzy caps like they used to!

So much for flame throwers! I will close the plug gaps before I go out again as you advised. Will likely swap it out. I found the Lucas coils quite cheap at a Mini web site.

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PostPost by: type26owner » Tue Feb 14, 2006 10:27 pm

Mike,
You need at least 3ohms minimum of resistance in the primary circuit of the coil for the hall effect switch to survive. Don't trust the parts guy to know what they are doing. Take your VOM with you to buy the new coil and test it right there before walking away from the counter.

The modern day glass-filled distributor caps are much better dielectric insulators by able to stand off at least double the voltage. Just no one makes them for our dizzies. I was really peeved that my son got for his 70 RoadRunner a state-of-the-art blue plastic cap with copper conductors for his car and I can only get old tech junk ones for mine. :evil:
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