Hey dude's.I test drove a 99 Civic SI the other day (nice car i might add) and i know somestuff about Honda's but i dont know a think about V-tec.So i just wanted to know if someone could give me a short run down on what it is, what it does and how it works?Thanks!

here's a link:
http://asia.vtec.net/spfeature/vtecimpl/vtec1.html

Your engine needs air for combustion but it needs dif. amounts depending on how fast it's going. Traditionally this restricted the efficiency of engines because the cam shape had to be able to provide a reasonable amount of air at idle and at redline. V-tec is basically a system of multiple cams so as the engine speed changes the Vtec computer fires a signal which causes a pin to slide into place via oil pressure and lock the cams used at low end to another cam so that the valve cycle is controlled by the new cam. This new cam is shaped for top end performance and would cause the engine to run crappy at low speeds. So when u hit a certain RPM ( I think 6k in the Civic Si) That surge you feel is the new cam locking into place and causing the valve timing to change thus giving the engine more air to use during combustion at high speeds. Some people will talk shit and say they have "Vtec" which they technically do but what they relly have is a SOHC (Single OverHead Cam) Vtec system. They have what I just described to you above but they only have it on the cam shaft that controls the intake vlaves. The DOHC (Dual/Double Overhead Cam) engines (H22, B18, B16 to name a few common ones) are the ones that people traditionally think of when they talk about Vtec for speed and power. These engines have the variable valve timing on both the intake AND exhaust valves. I'm not sure how much you already know about engines and stuff + it's late and I am tired so if any of this doesn't make sense or u have questions let me know and I will see if I can answer them.