Originally Posted by chip-3door

Would it be worth me mentioning really basic stuff like the fact the numbers are higher on the right than the left is that as RPM increases the volumetric efficiency of the engine naturally tails off thus resulting in a less full cylinder each cycle, hence being able to handle more advance as the PCP's will otherwise naturally start to get too late in the cyle and the power will fall off?

And obviously the same reason is true for why the numbers are higher at the bottom (less boost) than the top?

Or do we assume anyone who has read this far in knows the basics?

Is that the sort of "golden rule" you meant Stu, or something a bit more advacned than that?

Like maybe go into how cam timing effects it, or something like that?