Not trying to spam....register. That site is not just for hondas eventhough majority is honda.

An S/VAFC is a tuning device. It allows for manipulation of signals. Signals are measured in voltage. Airflow is a signal with equated voltage reading. Since airflow is converted into voltage reading, what the AFC does is manipulate these voltage reading. Now, how does this affect the timing? Simple, Honda ECU's take MAP inputs (once again, converted in voltage signal). MAP and/or vaccum condition in the intake manifold sends a signal to the ECU to advance or retard timing but you must take into consideration that these signals have to pass through the AFC first. Normally, AFC's are rigged in between the sensor and the ECU to intercept the signals for manipulation/compensation. Here's another explanation from TurboEF9 taken from the threads I tried to link you to:

"Why would people not believe? Lack of understanding? It's a simple concept. Your tricking your ECU into thinking you're at less pressure than you actually are. If you look at the flow of an ignition map, you're advanced down low, and you retard are you get to higher pressures right?

Well, lets say, you're at 3000rpm @ 10inHg. This would normally yield you ~27-30 degrees advanced on a stock PM6 map. Now, at that SAME RPM and pressure, depending on how much you're leaned out, your MAP sensor signal is scaled down with a V-AFC. Meaning less voltage (which dictates pressure) is getting to your ECU from your MAP sensor. So you could be anywhere from ~33-37 degrees advanced at the same physical pressure, and rpm!

Another side note, depending on how much you've scaled, you map not even be using your entire map. So, tuning for open loop would be difficult to say the least"