Ignition - What's needed
Firstly - re-runs or re-hashes of technical literary prose always brings to light either new, or old forgotten subjects for close scrutiny/re-examination. The arrival of 'A Well Known A-Series Tuning Bible' is no exception. Good news as far as I'm concerned as it keeps me gainfully employed!
This dissertation is centred upon that old chestnut 'ignition systems'. Technological advances running through the entire automotive world hasn't ignored the system that supplies life-giving sparks to bring your engine alive. It's true - no spark, no power. Much of the technology applied has been about making bigger, fatter, longer lasting, and more consistent sparks. The plethora of Mini spares suppliers have embraced this whole-heartedly as it's another string to their bows of profit generation. And it's this that's causing the problem - again Mini owners are being sold stuff that they don't need, or more pointedly will NOT increase power out-puts one iota. It's not necessarily the vendor's fault - ignorance is generally the reason they are trying to force the 'latest and graetest' upon you. So here's some enlightenment for you.
The Mini combustion chamber is very efficient. Consequently the standard coil-generated, distributor - well - distributed, points triggered ignition systems works very effectively - when new and properly serviced. When in good order, properly serviced and accurately set-up it's very hard to beat by any meaningful margin. However, the effectiveness starts to wane after only a very short period of time when degradation sets in. Much of the problem is centred on the distributor. Short term, the points wear/burn out, condensers break down, points heal cam wears, and eventually the distributor spindle bushes wear because of the relentless hammering of the points operation - particularly where poor quality aftermarket products are used. Without covering the more technical aspects of ignition system operation, the sum total of this degradation is reduced spark performance and consistency - and therefore power and economy.
From this, the solution seams eminently simple - replace the points with a more reliable trigger. But no, uninformed or greedy vendors would have you believe you need a system that will create what amounts to 'artificial lightening' within the confines of your combustion chambers to develop nuclear-fusion type mixture burns. And this, they assure you, will give you more power. Absolute rubbish. Oh, I've spoken to folk who swear by this or that system who are certain they got an immense power increase after replacing the 'old system' with it. I'll bet 'old' is the determining factor here. Anything replacing a poorly serviced and set-up ignition system will improve things no end. And the performance gains so carelessly tossed about that influenced them to part with their hard-earned cash were generated on other engine types with particularly poor 'burn' characteristics. The absolute best you're likely to get on a truly well sorted ignition system in a Mini will be 4%-ish, but more likely 2%.
The point is you don't need to invest fortunes in mega-spark producing systems in the good old A-series to get consistent, capable, and more than adequate sparks. If you can't be bothered/don't want the hassle of maintaining a standard points set-up all you need is one of the decent, reliable electronic ignition trigger systems readily available - such as Aldon Ignitor (Petronix), Piranha (Newtronic), or Lumenition. These eliminate all the points-generated problems with no maintenance required and can compensate for a certain amount of wear in the distributor. Lashing out more money than these systems cost will be a waste.
And the rest of the system? Lightening-bolt producing coils are just as unnecessary. A good 'sports' coil (Lucas Gold, Bosch Blue) is fine for the points-triggered system. A decent quality standard coil is all that's generally needed with electronic-triggered systems because the stable, consistent performance of these triggers maximises the sparking-power availability. Watch out here though - it's essential to use a coil suitable for your system. Late Minis have ballast-resisted ignition systems (See 'Ignition - Ballast-resisted). A standard 12v coil is no good on these.
HT (High-Tension) leads are another bone of contention. Seems like everybody's obsessed with 6mm/8mm and even 10mm 'silicone' plug leads. Sounds impressive but all it means is they've got lots and lots of expensive silicone-based insulation wrapped around the conductor to protect it from extremely hostile turbo-induced under-bonnet temperatures. Complete waste of time on a Mini where the HT leads are kept nice and cool behind the grille…And the conductor used is generally carbon-impregnated string - just like the standard, factory fitted leads so should be replaced yearly too. To maximise spark-production, you can't beat good old copper-cored leads with suppressed plug caps (NGK's are highly recommended) or a really decent aftermarket set like the Lucas 'Speedleads' range.
All that's left are the spark plugs. Again we are bludgeoned with 'power increasing' plugs such as these 'Splitfire' items sold at over twice, may be three times the price of a 'standard' plug. And again - in a Mini; worthless for all the same reasons artificial lightening isn't needed - the very efficient combustion characteristics possessed by the A-series engine. A decent, standard-style plug will suffice - and once more NGK give consistently better results than any other in the A-series I have experienced so get my vote.