[Christ]

It's technically the same volume of air in a closed circuit entering under more pressure.

Without proper tuning, and given some circumstances, it can cause your engine to lean out a bit, and your ECU WILL compensate for it, provided you're at a throttle position that requires it.

Since harmonics tuning works at any RPM range, and at any throttle position (other than closed) at any RPM range (with a lesser effect for lesser throttle, due to lesser amounts of air coming in, and less of a compound effect) the idea is that at cruise, you're at less than 20% throttle, and the resultant harmonics is enough to accelerate the same amount of air coming into the combustion chamber, therefore, it just increases the engine's VE at a specific point, rather than actually increasing the power. (Less pumping losses, not more power.)

It's kinda like when the electric company gives you a break at night b/c you're off peak. You're not actually using any less electricity, but you're paying less for it.

Your engine isn't working as hard to draw in the same amount of air, but it's making the same amount of power it was before... this results in an excess, which shows up as more torque.

Loudspeaker analogy - You have a 10" Sub in a vented box, and a 10" in a sealed box, both of optimal size and construction for the same sub, all things equal.

The 10" vented sub will have a specific frequency where it just hits SO MUCH harder than the sealed one. This is b/c of resonance. With a specifically tuned port (intake runner) the sub (piston) at some point in the harmonic range will be moving outward just as the influx of pressure is moving into the box, and will rebound inward as the influx of pressure is moving out of the box.

What this means is that while the sealed box has good all-around sound (like a normal, untuned engine), the harmonically tuned vented box will often have a smoother tone, hit harder, and create much cleaner notes on a given range ("bump" at certain freq).

The reason for this - when the influx of air is moving in at the same time the sub is moving out, the sub doesn't have to create a low-pressure area in the box to move. This means that it's using less kinetic energy (from electro-magnetic energy) to move in the outward (bound) direction. Using less kinetic energy to do the same job means that you're more efficient at it.

(Just for you Akashic!)