A different way of looking at it. There are other factors too. First the basics. It's all about peak torque. Because HP is torque x revs, having peak torque at low revs results on high HP at lower revs and "lower than possible" HP at high revs - a good spread of HP. That's a stock VW tactic. Peak torque is based on Volumetric Efficiency. Putting aside the myriad of other variables that effect VE, the cam does it like this... When the piston reaches the bottom sucking in air, the air is lagging behind and there is a vacuum in the cylinder. There is still a vacuum as the piston starts to rise. The ideal time to shut the valve is when pressure has equalised, just before the piston starts blowing it back out again. The higher the rpm, the later that equilibrium is attained so the later you want to shut the valve to take full advantage. A stock type-4 cam inlet valve closes at about 35° ABDC which produces torque and HP like this, though this is a 1600 twinport at 37°ABDC. The equivalent single port is worse on all counts which rather debunks that that theory of single ports being more "torquey".