Does i-vtech even kick in at a certain rpm, or is just v tech engine?

[MattTran]

i have base rsx 2006, i-vtech engine...not sure when does it even kick in if at all, how would i notice the change?

I thought i read somewhere before i-vtech does not even kick in at all, and you can not feel the difference, but im new, do not know what i am really reading, any insights