Since the A-Series has such an efficient combustion chamber design, the standard points set-up is perfectly capable of providing sufficient sparks for effective combustion when new. And this is the problem. They require regular servicing to maintain maximum performance. This can be a chore, so is generally neglected. And it doesn't take long before deterioration seriously affects performance. Points bounce is also a problem on high-revving race motors.
Deterioration of the points set-up can be caused by several factors - wear and tear on the dizzy spindle bearings creating 'wobble', electrical erosion of the points, and wear of the points cam heal. All have the same effect - dwell angle alteration. This in turn reduces spark effectiveness. The consequences are a loss in power and economy, poor starting performance, and general poor running.
To maximise spark potential an electronic ignition is essential. Many years of development within the electronics industry and automotive applications, have produced very reliable, effective switching units. They are not influenced by spindle wear (providing we’re talking thousandths of wear here - not inches), and do not suffer degradation by arcing or bounce at high rpm. In short - very accurate and consistent switching for the all-important spark. Needless to say there are a number of different types on the market, using different ways to switch the ignition. Originally most designs were transistor assisted contact types - using the points as a low voltage switch to trigger them. Technology has moved on, so these are now a rarity. All high quality, low cost electronic ignitions are light or magnet triggered. Following - in alphabetical order - is a résumé of what's available.
Their original system was first conceived for use by the MoD, but soon applied to systems for general automotive use. Three main pieces are involved - finned aluminium power pack, optical ‘eye’ that mounts to the dizzy base plate, and a chopper rotor blade. The blades of the chopper interrupt an infrared beam as it rotates, providing the switching. The finned aluminium power pack charges the coil. The fins dissipate heat generated by the transistors when in action. Although known to be durable, it's now a little costly in comparison to its competitor's offerings.
They also now do the 'Magnetronic' ignition module type. Effectively brought out to combat the highly successful Petronix unit, it features similar operating method, components and connections - all fitting under the dizzy cap with two coil connections. Even down to the fact that it isn't available for the Ducellier dizzy either. Consequently it's cheaper than the original outlined above.
This has got to be the simplest, neatest, value for money system currently available. Consisting only of two pieces - the trigger ring that fits over the cam under the rotor arm, and a plate that screws to the existing points base plate. On this plate is mounted the pick-up and transistor. Consequently it all fits under the distributor cap, and has only two connections to make. One to either side of the coil. Small cam-ring mounted cobalt rods passing the pick-up do the switching magnetically. Doesn't require a high-power coil, the standard one is fine. Excellent for street and race use. Those with concourse quality cars that want the reliability of electronic ignition but without extra power packs and connecting wiring in the engine bay - this is for you. The only drawback here is they don't do a kit for the Ducellier dizzy.
Many moons ago this system was blighted by unreliability, but was soon sorted out and became Lumenition’s main competitor in the electronic ignition world where cost effectiveness was a consideration. Again there are three main pieces involved - power pack, optical eye, and triggering disc. Although working on similar principles to the Lumentition, it differs in as much as the infrared beam is off most of the time, being turned on by a passing slot to effect the switch.
Out of curiosity I posed Piranha the question ‘why’ about this some moons ago. Their answer seemed to make common sense really. They stated that as accuracy was the name of the game, a light that is switched on has a smaller ‘grey area’ than one that is switched off. ‘Eh?’ I said. Think about it. When you switch a light on, it illuminates instantaneously, where as when you turn it off it sort of fades out - like a cars headlights. Being even more curious about this I put this to Lumentition. They said that the infrared beam went on and off so quickly, it wasn’t at all like a normal light, and what ‘grey’ areas there may be are sorted out by the electronics in the power pack.
For my money - it's the Petronix kit. For Ducellier dizzys, the Piranha