Old Grey wrote:Only the big boys can treat each cyl as an individual engine, because it takes a lot of resources and money.
I must completely disagree with that. Every engine should be treated as multiple one-cylinder engines, as that is the only way to get the most out of each, and therefore the whole, for any application. This is true whether it's a commuter car or serious comp car. Individual cylinder ignition trim (I will call it ICIT) is very handy to average tuners, as you can see issues or opportunities and take advantage of them.
Example - you are tuning your weekend Honda turbo rocket on pump gas. You make a back-road run (or dyno pull, or track run) through a gear and check your plugs. #3 shows light signs of detonation, so you pull a couple degrees from that cylinder, advance the Spark Table for the rest of them and run again, repeating this a few times until the cylinder that needs the most is at its peak, and the rest are variously retarded for their peaks. Bingo. Minimum timing for best torque on each cylinder
for max power, and all in a matter of minutes on your local back road or whatever. The alternative is to run timing for all cylinders based on the weakest one.
More mundane? Perhaps you have an engine that is not blueprinted, and it has typical variance in effective compression, or uneven cylinder heat, or uneven port flows, or some leaking rings on one piston or one valve stem seal sucking oil—all capable of being individually tweaked just for reasonable running without being as lame (better mileage or power), or prone to det (better power and less damage), or whatever it's problem is. The price is your time. It's really no different than using cylinder fuel trim (ICFT), simply giving each what works best, and useful to anyone with an engine that isn't perfect from cylinder-to-cylinder, and whether using det-limited fuel or not. IMO that includes almost all of us.
PS: A warm-dry compression test will tell you right-off which cylinders will likely need more or less timing to make best torque, simply by observing dynamic compression as one factor.