Originally posted by PHiZ
I dont' think there is any such tahing as 3-stage vtec, I think what you're reffering to are the IABs in a H22 or B18c1 motor.
There is 3-stage, though I don't think it's been around in North America. But in Japan. May have been on some European models too, not sure.
Basically 'regular' VTEC + VTEC-E. At low RPM, only one intake valve opens (similar to VTEC-E on the HXs). At medium RPM, two intake valves open using a mild profile, and at high RPM, you get a more agressive profile.
Can't find a link right now, but if you dig around a bit you can find it.