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vtec is honda's variable valve system, it adapts for fuel economy or power when needed.

when your car is accelerating very fast, the Vtec system allows more air and gasoline to enter the cylinder for more power.

when you drive on highways or accelerate slowly for fuel economy, the vtec system uses smaller valves to easily spread out the gasoline and air so that it burns completely.

you may not understand my explanation but what it means for you is: fuel economy when you need it, and extra power when you need it.

It's one of the reasons the honda civic is so fuel efficient, you can expect 35mpg with an automatic transmission, and 40mpg with a manual transmission

actually to put it in english Vtec is a performance/economy set up on your engine. Basically what it means is your car has 2 stages. If you drive normal, your vtec will stay off and you will get alot of miles to the gallon. If you feel like having some fun when the traffic light turns green then when you floor the gas peddle, the Vtec will turn on and you will haul ***! Thats basically what Vtec is. To be alittle more in depth you have a 2 stage cam set up. Your engine uses smaller cams when vtec is off and your drive normal, and switches to the bigger cams when you want performance. WELCOME TO THE WORLD OF VTEC!

In somewhat simple terms, the camshafts allow intake valves to open and let air/fuel into the engine and they also allow the engine to to expel the burned air/fuel mixture through the exhaust valves once it's burned. Camshafts that are fixed in profile (non-Vtec cams for purposes of this discussion) can either be tuned to deliver smooth operation at lower RPM with the sacrafice being higher RPM power, or they can be tuned to deliver higher RPM power with the sacrafice being low RPM smoothness and poor emissions performance. A fixed cam profile simply can't be optimized to both deliver high RPM power and smooth low RPM operation.

With Vtec, Honda uses a system with 2 different cam profiles - one profile for when the engine is running slowly or under light loads, and a second profile for when the RPM is higher to make more power. The Vtec system essentially allows Honda engineers to use one cam profile for low RPM operation so that the engine runs smoothly at low RPM and a second, more aggressive cam profile for higher RPM power output without having to sacrifice smoothness/emissions/power at low RPM.

VTEC stands for Variable Valve Timing and Lift Electronic control

there are different variants of VTEC, so each effects the Performance differently, for those of us in the honda tuner community VTEC is the holy grail, VTEC in performance DOHC engines (two sets of camshafts) found in civic type-r's and sports is more aggressive and has a crossover point where it switches to a higher cam lift profile,

cams operate the valves in a cars engine and in performance VTEC engines they have two lobes that operate the valves per valve, at high RPM (5,550 +) the second more aggressive lobes come in and lift the valves more open, allowing higher fuel/air flow into and (in DOHC engines) out of the cylinders, resulting in a more powerful combustion which = more power, simultaneously the engine also varies the valves timing (them letting in fuel and letting out gases) to sync them with one onother to optimize fuel flow....it comes in at 5,550 rpm as at lower RPM the engine isn't buring enough fuel to cope with the higher fuel imput VTEC provides, also an aggressive cam profile as idle/low speed makes for a rough idle and bad ride (race cars will idle irregularly, thats why!)

in lesser performance engines, like SOHC engines, (single camshaft) VTEC works only the inlet valves and comes in in less noticeable stages rather than the one crossover as in more powerful engines...

sorry if thats a bit complicated, I explained it in my own words but its impossible to understand the system without some basic engine knowledge, put simply VTEC = better performance, but a MASSIVE increase in the sport engines, trust me -- it makes a difference!

if you mean the 1.6 civic LS then its 3-stage VTEC that doesn't affect perofrmance massively, it helps fuel economy whilst having a positive affect on performance,

if you mean the 1.6 civic VTi/Si then it has the better more performance oriantated VTEC system

search VTEC on youtube, or 'civic VTi', you will hear VTEC engage at around 5,000 rpm