The annular area is tiny at 0.006". Don't you think that this is the point where you can say that the valve has moved off of the seat and gives the largest duration number? Its the marketing duration point.
I don’t know another way to say it. Did you think about it?
Let’s just look at the exhaust valve.
I’m just pulling a number out of my *** but let’s say there is 500 psi in the chamber 1 degree before the valve opens. Now move the valve .006 off the seat.
What happens to the pressure?
Stop and think about it. When the valve cracks the seat the pressure changes.
So it matters exactly when the valve opens and closes.
These engines run off of pressure differential. So when the valve leaves the seat shut happens.
And the engine knows it.
Slow lobes are easier to control at higher rpm but they kill torque at low rpm.
You need to forget what you think you know and think in terms of pressure differential.