I guess I was too specific and also incorrect at same time.
Does dynamic compression ratio even matter except at idle?
Doesn't actual compression depend on RPM and flow characteristics of the engine?
Will a 8.5 DCR turn into 10+ DCR at Peak RPM?
No, your DCR is determined by your cam event's only. Cylinder pressure is RPM dependent.
There is a relationship between static compression ratio (ie 11.5:1) and cylinder pressure (ie 195 PSI). One problem is that cylinder pressure can be expressed in a few different ways to describe different things.
What most people refer to is cranking pressure ( measuring the cylinder pressure with aguage while turning the engine over)which is affected greatly by what cam you have. Not only the duration but also the opening and closing points. You can have two engines that are identical in every way, to include the same measured and calculated static compression ratios ( say 10.8:1) but different cams and they can have VERY different cranking pressures!
Taking it one step further is an engines Break Mean Effective Pressure (BMEP). which is a measure of the average cylinder pressures generated during all four engine strokes (for a 4stroke obviously). It is always highest at max torque as that is when an engine creates the highest cylinder pressure and instananious power regardles of engine size and operating RPM. Here things get complicated as BMEP is affected by all of the aspects of an engine that influence getting air in, adding fuel, compressing it, igniting, and expelling the gases, along with the thermal properties of the engine. The gas velocity ram effect of an intake manifold and the "tuning effect" of different headers are examples of altering an engines BMEP. The faster an engine turns the less time it has to fill the cylinder, how the cam,intake and exhaust allow it to get the gases in and out will determine at what RPM an engine achieves BMEP and consequently max torque. Where this gets tricky is time. As an example, one engine that reaches a max BMEP of 210PSI @4000RPM will have less power than one that reaches the same max BMEP @ 6000rpm. although both engines are creating the exact same downward pressure on the piston the faster engine is doing it more frequently AKA horsepower (Torque over time).
I've glossed over alot of very involved subjects quickly and have poorly represented the topic but it's a start.
The best book I've ever read on the practicle application of engine performance is "Four stroke tuning for performance" by A. Graham Bell. If your really interested in the science of making any car fast for any type of competition it's hard to beat.
)for maximizing air flow in hard to reach places.
