My 3.6 v6 that makes 288 hp has 11.5:1 compression and uses 85 octain just fine. That is somewhat the VVT but also a lot of the direct injection. Now they can even eliminate the throttle plate all together and control rpm and ignition with fuel like a diesel. With the VVT, the can timing itself can be constantly adjusted, there are even aftermarket tunes to replicate a "thumper" can by adding overlap whenever you want, or a velvet smooth idle. The 4 valves per cylinder means a Hemi style chamber with opposed valves but also a larger overall surface area for airflow but the individual smaller vavles mean less shrouding then 2 large valves.