GOOGLE http://auto.howstuffworks.com/question229.htm

Not too complicated is it!

VTEC 10 years ago and today is the same. Only slight adjustments to improve
power or feul consumption have been made since. But the basic are the same.


"User" <user@email.address.here> wrote in message
news:43c009d5.175143359@netnews.att.net...
> Yeah, I know it's some sort of variable valve timing. But exactly
> what is it as implemented in my 2006 Civic LX? I've done a lot of
> searching on the web, but I can't find my answers.
>
> When does it activate? Is it a smooth, continuous action, or is it a
> step change in configuration at some engine speed? Is it somehow
> changing the fulcrums of the rocker arms? Is it rotating cam lobes on
> the cam shafts? Is it rotating the cam shaft relative to the pully
> driven by the timing belt? Is it selecing different cam lobes? Is it
> a change of the valve lift? Opening only? Closing only? Is its
> activation a function of engine speed only, or load, throttle
> position, airflow, etc.? Is it done with solenoids in the head, or is
> oil pressure used?
>
> Any pointers to detailed engineering descriptions would be greatly
> appreciated.
>
> Thanks.
>