Stock CDI limits are anywhere from 7800 to 8000 rpm. An aftermarket can be of 9000 to no limit at all. The rev limit will not factor in on a stock or lightly modified engine since the power curve is around 7000 t0 7800. Above this no power is produced, unless the engine is modified mainly in the head and camshaft. If your engine is modified moving the power curve up the scale then a higher rev limit or no rev limit will be desired. But your not likely to make any power much over 9000 rpm and this will be with a heavily modified motor. The cdi has 3 main functions 1) controls timming advancment of the spark, 2) controls duration of the spark, and 3) controls the rev limit if so equiped. The main thing to look for in a cdi is the advance curve and the duration of spark for the idea is to burn the most fuel at the proper time which produces power. An average non computerized engine will only burn 80% of the fuel due to several factors, this creates hydrocarbons. EPA limits these hydrocarbons by running lean mixtures. Also stock engines naturaly asperated (carburated) will only fill about 60% of cylinder capacity, about 70% with a turbo and 95-100% with a super charger. The object is to pull as much fuel and air in the cylinder and burn as much as possible. This is what creates power. There is not any one part that will make a huge differance, it is a combination of things needed to be done to make noticable power, and this will depend entirely on your budget.
TOM
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