[Brian R.]

Advanced cam timing shifts the torque curve upward to higher rpms, which makes the engine more powerful at higher rpms. The cost of this is less drivability and torque at lower rpms. A test for correct operation of the VVT system is to activate it at idle. The engine should idle rough or die because the high-rpm cam timing is not suitable for low-rpm use.

Conversely, a cam timing/lobe profile that is good for mileage and low-rpm torque is not optimum for high-rpm performance - the engine doesn't breath as well.

With the VVT system, you have a good low-rpm cam profile/timing. The system is changed at some rpm (4000 or so) to give a more aggressive cam timing, increasing the high-rpm torque/performance.

When low oil pressure prevents the cam timing from changing as it's supposed to, it is not adequate to protect the engine. The only way to really protect the engine is to shut it down. Keeping the engine from creating maximum hp at low oil pressure is just a by-product of the VVT system.