Valve Timing Chart

In my never ending quest for good cam/valve timing data, I am continually let down by the offerings of the media and by self proclaimed 'experts'. It seems that they always end up focusing solely on duration values as the main driving criteria. There is very little consideration given to the engine combination. Just the interaction of intake port velocity to the cylinder volume is enough to render most of these offerings as useless.
With all the articles out there, I decided to do the same. Therefore, I put together a chart that shows the interaction of the engine combination to the valve timing specifications. The chart presents a generic look at valve timing events and shows how port velocity and exhaust pressure effect the overall timing events. If you are looking for math Cal's or background information, you will not find it. The chart was not intended as a design tool, but rather a simplified look at the valve timing process that I feel is important.

I do need to briefly explain the chart. The values of port velocity and exhaust pressure are highly dependent on the engine size. What is high velocity for one engine/head design, may not be for another. So the interaction of engine size is written all over this chart, although it is not apparent by casual observation. The one value that I have been able to actually determine as being semi-constant for all engines is the intake closing angle. An interesting observation is to note how the overlap demands change as the relationships change.
A simplified way to use this chart is to pick out a set of timing events (a guess is fine, but seat timing events will work best) and then look at what happens to the timing events as different parameters are changed. Look at what happens when you increase the exhaust capability, increasing the exhaust to intake ratio. The exhaust opening needs to be retarded, otherwise the motor will sacrifice cylinder pressure from too early of an exhaust opening. In retrospect, what is a classical complaint when putting a too large of a header on a engine? It looses low end torque. With a chart like this, those sort of issues become clearer.
So for what its worth, here is the chart. I hope the reader/viewer gets as much pleasure out the chart as I did making it. It was strange trying to present a idea without using any math to demonstrate the process, but I feel it serves it's purpose adequately.