Moving in the right direction here. One simple explanation i use is comparing to a slingshot. First the Groove holds some air back, then releases it. Vacuum intensification, then a pressure wave. Fuel evaporates better in increased vacuum, the wave is beneficial turbulence. There is another dimension and question.
I remember studying about carburetion, reading of wavefronts. The intake valve opens and a pulse generates in the intake tract. It moves down from around the throttle plate(s) to the intake valve. We're imagining this in slow-motion. The pulse or wave front goes down and strikes the back face of the intake valve, some goes past the opening valve rising off it's seat. Some reflects back off the valve backside and goes back UP the intake tract. Another pulse forms going back down, and so on. On High-performance racing engines w/ big cams and carb's, an effect called Reversion can happen. The pulses can generate a fuel vapor cloud just above the carburetor, called fuel Standoff. There's a picture of this effect in my old Holley Carburetors and Manifolds book.
These pulses or waveforms move at sonic or near-sonic speeds. If you've ever been under the hood on a running engine in park or neutral, and gunned the throttle suddenly, that BWAAAHH sound is those waveform pulses. Intake manifolds and cams are designed to work in given RPM bands, and manifolds use resonance (the Waveforms you hear) tuning in their designs.
what I'm saying here- is there isn't just ONE waveform pulse, but many in each cylinder intake stroke. That means, the Groove might get more than one crack at it in each Intake stroke. Or, I'm wrong here, and the air vortices continue building in the Groove until 90 deg. crank angle, then let go. This multiple waveform pulse thing has been in my head for years now. Do we get more than one Waveform out of the Groove in each intake stroke?
Kinda crazy trying to figure all this out. We KNOW it works, just not all of how.
On AFR, it's changing constantly. the ECU is trying to keep in a theoretical ideal range. Juan, Ron says, and it stands to reason, that the waveform pulse does (or Pulses do) help even out the mixture distribution in a combustion chamber, making for a more complete burn. Almost a weak supercharging effect, I think.
One last thought. The Nitrogen in the air, doesn't aid combustion, BUT- it and water vapor, get heated and are what are expanding in the combustion chamber. The expansion medium. Think of Nitrous. Nitrogen and Oxygen gas compound. Extra O2, with added fuel, burns more intensely, heating more Nitrogen. More pressure, more power.