Tuning Dynamic Camshafts (VVT, AVCS, Mivec )

Introduction
Tuning the camshafts are a main ingredient in getting the desired performance from an engine. The camshafts determine a few behavior in the valve-train:

1. The overall valve opening timing event
• The point at which the valves starts to open in relation to the crankshaft degrees.
2. The duration 
• How long (crankshaft degrees) the valve stays open for.
3. And the lift (or sink)
• How far down does the valve go to allow more or less air to pass by it into the chamber.

While duration is fixed, the timing and lift can be altered to a desirable behavior from the engine.
These controls can be optimized for various engine speeds (RPM) and loads (the amount of air flowing compared to the theoretical maximum). Car manufactures realized that while either advancing or retarding the camshafts, the engine would make more or less power at a specific RPMs. The problem though, is that they either have to sacrifice low end power for top end, or vice versa, as a car which has its cam tuned for high rpm would usually see low performance in the lower RPMs.

One Setting Doesn't Suits All
Car manufactures realized that by carefully advancing or retarding the camshafts, the engine would make more power at a specific RPM, but as the engine leaves that RPM band the benefit is lost. While cam gears allow a tuner to change the overall valve opening timing event outside of the manufacturers' setting, this will still only benefit a narrow area in the powerband.
Additionally, fuel economy and emissions are also affected usually at the cost of performance. Manufacturers are challenged on deciding a cam setting that gives a good compromise between emissions, power and fuel economy.

The solution:variable valve timing
New technology allows valve timing to be variable/dynamic: the VVTi, AVCS, i-VTEC, and MIVEC technologies! Most of these work in the same way: they have an oil controlled valve that advances or retards the camshafts as is suitable for specific engine speeds and loads. 45 degrees of variation in advance/retard is not unheard of in these systems, as some allow even more.

How to tune the dynamic cam system

The basic idea of variable valve timing is to give the best of all worlds. It gives the tuner the opportunity to make a little more power over the entire RPM Range. Here is an image that depicts what the engine is doing at various cam settings: