AndyRST

and dont say it varies the valve timing, because i guessed that in the name of it

Can someone explain it (in a technical but easy to understand way please stu, karl, etc ) and how it acheives the varied valve timings on say a Focus ST170 ??

Cheers

philc

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

Jim Galbally

uses va va voom

AndyRST

So how does the cam timing adjust then ?

Jim Galbally

without reading that howstuf works page...

cam has 2 sets of lobes (so say 8 valves, you have 16 lobes) in normnal running half of them are in contact with the valves, and have "normal" profiles... all's happy

when you start caning the shit out of the c the cam physically moves across a bit (so moves sideways) which will mean the normal profile lobes are no longer in contact with the valves, and the new more meaty lobes are touching the valves...

feck knows how it moves, or even if im talkin about the right type of thing (iirc vtec and vvti are actually different, not just different names for same thing )

but thats how i understand it

Alps Pacino

my crx vtec actually had 3 lobes and 3 rocker arms 2 big 1 little on the exhaust side per cylinder, and the cam does infact move across. Me and me mate took his head apart after he blew it up to see what the crack with the vtec was, and still couldnt work it out with the head infront of us. I think you need to look at it with slanty eyes to see how it works

markk

iTrader: (2)

lol !!

try by hydraulic pulleys (usually just inlet ) can work by oil pressure (early type oil pressure alone -simple on of ) tho not stricktly call variable valve timing , another way is to duty cycle a solenoid to create a pressure sensetive gallery to which the cam will be forced against a spring to advance or retard camshafts !!

Dan B

This explains VTEC nicely, I thought:

Video-clip (2.4Mb)

AndyRST

Dan that video clip explains things really well, thanks for that!