It is simple, tha vtec conrloler let you regulate how much air and gas you whant's to go to your motor, le you start your vtec on any rpm you wnat. i recommended on a 2,500 or 3,000 that make you vtec work at full.
It's possible. However, if you're not willing to dish out the cash for a proper build, don't waste your time. A cheaply converted non-vtec motor will not last long and will have A LOT of problems....