Coils, plugs, wires - among my favorites! We'll ignore tune-up type stuff and just discuss the components.
All that is necessary to fire the fuel/air mixture is a sufficient spark at the right time. It is the heat of the spark that ignites the fuel/air mixture (hotter is better). It is the gap of the plug that determines how big a spark is exposed to the mixture. A bigger gap is better IF the coil produces sufficient sufficient voltage to generate a spark to cross the gap. The wires have to ensure the voltage from the coil gets to the plug without losing too much energy along the way and without leaking to ground or cross jumping between wires.
If someone said to me, you can change only ONE item of this group to a "better" quality, it would be the wires. ANY spark plug of the correct heat range and reach properly gapped will fire the fuel/air mixture Any modern coil will generate sufficient power to jump a standard gap. But the wires degrade over time and often the degradation is not obvious.
High performance spark plugs have two "advantages" that may or may not be relevant. If you change plugs every 5000 miles, forget about them. But there are two types of plugs that can be helpful. Platinum tip and multi point plugs.
The platinum tip advantage is that the gap does not widen due to wear nearly as fast as with standard plugs. The multi-point plugs use another method to do the same thing - they typically have 4 ground electrodes. Some people believe that they all fire and therefore provide more spark area. This is not true. The spark jumps the narrowest gap. Initially, if the gaps are (as they should be) all the same, the spark may jump any of the gaps randomly. This is NOT necessarily a good thing - more later. As a gap widens from wear and that side of the center electrode begins rounding off, the spark quits jumping that particular gap and uses a different one. So obviously, the plug can run much longer because it essentially has more optimim gaps available.
When searching for maximum performance, spark plugs are "indexed." That is, standard (single-electrode) sparkplugs in the engine are set so that all plugs have their ground electrode oriented in the same direction. This is a pain in the butt but it's worth a few HP. Obviously in a 4-electrode plug, this is impossible because you can never know which of the 4 gaps the spark will jump. So...multi gap and platinum tip plugs are good for long service life which is a good thing. They do nothing for improving performance over standard plugs but they will hold the performance longer.
Another aftermarket device related to the ignition that clearly does demonstrate performance improvements in certain circumstances is multi-spark ignition modules. These actually generate a series of individual sparks in extremely rapid succession for each spark plug. They require hotter (higher voltage output) coils and corespondingly better wires. If you used poor wires and an MSD, you would get the benefit of an amazing light display under the hood at night as sparks jumped hither and yon but that would be about it. MSDs improve performance because they provide a larger area of spark(s) to ignite the fuel/air. This ensures a more efficient burn across the flame front, increasing power and reducing the chance of detonation.
More (larger) spark is better assuming it is delivered at the right time. Therefore, larger plug gaps are better IF the coil and wires can deliver the voltage to jump the gap. This is why fuel efficiency improved with electronic ignitions and better-controlled systems in general. Gaps went from the typical .035" to .065" and larger. Longer spark = better efficiency.
OK, now...If I add "better" coil, wires, plugs, do I get more power? Actually, a better question might be, If I add better coil, wires, plugs, do I get more "noticeable" power? A safe answer is, "no,assuming your stock system is operating up to specs." Hi performance ignitions really go with increased engine compression. The higher the compression, the harder it is to fire the spark - that's their real advantage. With a stock engine, adding hi performance ignition parts won't do much of anything except reduce the frequency of replacing the components. And even this is questionable on any late model engine; they all have quite good oem ignition systems - largely courtesy of the EPA!
A good check, requiring no instruments at all, to see if your ignition system is reasonably healthy is to simply lift the hood an night with no lights on. If the car is running well and you see no sparking under the hood, it's fine. I say if the car is running well because you could have certain situations where a wire is totally grounded and is therefore not sparking. However, if this is the case, the engine will be running obviously rough.
If you are electronically inclined and wish to do so, you can also check the ignition wires for resistance - 7000 ohms of resistance per foot of wire is a fairly standard spec. Anything higher is cause to consider replacement. Do not replace resistance wires with solid core wires. All you will get for your trouble is interference in a variety of electronic components and radios. You will NOT get a better/longer/hotter, whatever spark. There are superb resistance wires available and most oem wires are of this sort. The days of the old carbon-impregnated wires, which were justifiably and instantly replaced when you got the car home, is long gone.
I've rambled on long enough I suspect...
It's obvious that work here wasn't too challenging or busy today...
